THE DEV ELOPM EN T OF THE EMBRYO, ENDOSPERM, AND
PERICARP OF THE PEACH (PRUNUS PERSICA, SIEB. Z U C C .) AS R E L A T E D
TO FR U IT THINNING WITH PLANT REGULATORS

By

PO RTER BRONSON LOMBARD

AN ABSTRACT

S u b m itted to the School fo r Advanced G ra d u a te Studies of M ichigan
S tate U n iv e rsity of A g r ic u ltu r e and A pplied S cience
in p a r t i a l fu lfillm e n t of the r e q u i r e m e n t s
for the d e g re e of

DOCTOR OF PHILOSOPHY
D e p a r tm e n t of H o r tic u ltu r e
1958

A p prov ed

PO RTER BRONSON LOMBARD

ABSTRACT -

A s e r i e s of stu d ie s w e r e con ducted d u rin g the p e r io d of y e a r s from
1955 th ro u g h 1958 to d e te r m in e the tim e of a p p lic a tio n and the v alu e of naphth a le n e a c e tic a c id (NAA), N - 1 -n a p h th y lp h ta la m ic a c id (NPA), and 3 - c h lo r o i s o p r o p y l-N -p h e n y l c a r b a m a t e (3 -c h lo ro IPC) fo r b lo ss o m and f r u it thinning of
peaches.
A p p licatio n s of NPA d u rin g 1955 th ro u g h on R edhaven and H aleh av en
p e a c h t r e e s a t 200, 250, 300 and 400 ppm th re e days a f te r full bloom did not
r e s u l t in su fficien t th in nin g to e lim in a te hand-thinning, except fo r the r e s u l t s
fro m the a p p lic a tio n s of NPA at 300 ppm on R edhaven t r e e s in 1956 and 1958.
T he u s e of 3 -c h lo ro IPC at 400 ppm on Redhaven and H alehav en t r e e s fo u r
w eeks a f t e r bloom in 1956 and 1957 r e s u l te d in h a s te n in g f r u it rip e n in g and in
u n fa v o ra b le Mbeaked" p e a c h e s , but did not thin su fficien tly to e lim in a te handthinning.

NAA at 30 ppm ap p lied 42 days a f te r bloom, two w eeks a f t e r ” shuck-

off", in 1957 and 1958 r e s u l t e d in sig n ifican t fru it thinn ing on R edhaven and
H aleh av en t r e e s .

An a p p lic a tio n of NAA on Redhaven 35 days a f t e r bloom at

30 ppm r e s u l t e d in sig n ifican t thinning, w h e r e a s an a p p lic a tio n of NAA 49 days
a f t e r bloom r e s u l t e d in no a p p a re n t thinning.
An a p p lic a tio n of NAA a t 30 ppm 42 days a f t e r bloom on R edhaven
and H alehaven t r e e s in 1957 sig n ifican tly re d u c e d the n u m b e r of flo w er buds
in the s p r in g of 1958.

ABSTRACT - 2

PO RTER BRONSON LOMBARD

A study w as in itia te d in 1958 to c o m p a r e the n a tu r a l drop of b lo s s o m s
and young f r u it s fro m R edhaven p e a c h t r e e s with the drop r e s u l t i n g fro m the
u se of NAA and NPA a s thinning ag en ts.
The daily b lo ss o m drop of the c o n tro l t r e e s w as h e a v ie s t d u rin g a
sev en day p e r io d one w eek a f t e r bloom .

M ost of the drop fro m the Redhaven

p e a c h t r e e s , which r e c e iv e d an a p p lic a tio n of NPA a t 300 ppm t h r e e days a f t e r
bloom , took p la c e d u rin g th is sa m e p e rio d .

T he "June" drop of the c o n tro l

t r e e s a p p e a r e d in two p e r io d s of heavy fru it drop, the f i r s t p e r io d o c c u r r e d
a p p ro x im a te ly 35 days a f t e r bloom and r e m a in e d co n sta n t fo r 14 days.

The

secon d p e r i o d of "June" drop o c c u r r e d about 49 days a f t e r bloom and l a s te d
f o r 11 days.

An a p p lic a tio n of NAA a t 30 ppm 42 days a f t e r bloom a p p e a r e d

to delay the secon d p e r io d of "June" drop by t h r e e days.
A n ato m ical in v e stig a tio n s m ad e in 1958 on R edhaven p e a c h e s r e v e a le d
th a t sy n g am y took p la c e betw een sev en and 14 d ays a f te r bloom .

The peach

e m b ry o of both the H aleh av en in 1957 and 1958 and R edhaven in 1958 continued
in the fila m e n to u s stage, l i n e a r in shape, for a 2 8 -day p e r io d .
v elo p ed im m e d ia te ly a f t e r the f i r s t divisio n of the zygote.

T h is fo rm d e ­

T he e m b ry o b e c a m e

bulbous in shape, the s p h e r ic a l stage, a p p ro x im a te ly 42 days a f t e r bloom
and con tinu ed fo r about sev en days.

R apid grow th of the p e a c h e m b ry o w as

o b s e r v e d about 49 days a f t e r bloom d u rin g the tr a n s itio n a l stag e, when the

PO RTER BRONSON LOMBARD

ABSTRACT

e m b r y o chang ed to a tr ia n g le shape.

C e llu la r f o rm a tio n of the e n d o s p e rm

o c c u r r e d about 42 days a f t e r bloom .

The se e d and p e r i c a r p of the p e a c h

continued to grow a t a r a p id r a t e fo r a p e r io d of 49 days a f t e r bloom when a
s h a rp d eclin e in g row th o c c u r r e d .
Diethyl e t h e r e x t r a c t s fro m p e a c h s e e d s c o lle c te d from R edhaven
t r e e s fro m June 2, 1958, four w eeks a f t e r bloom and at w eek i n t e r v a ls t h e r e
a f t e r f o r a p e r io d of four w eeks, r e v e a le d th at the n a tu r a l h o rm o n e content
of the a c id and n e u tr a l f ra c tio n s r e a c h e d a m ax im u m in quantity six w eeks
a f t e r bloom .

F r o m v a r io u s q u a lita tiv e t e s ts , it a p p e a r e d that the n a tu r a l

h o rm o n e p r e s e n t in the a c id f ra c tio n w as not IAA, how ever, t h e r e w as a
s tr o n g in dication that the n a tu r a l h o rm o n e p r e s e n t in the n e u tr a l fra c tio n
w as EtLA.

TH E DEVELOPM ENT OF THE EMBRYO, ENDOSPERM, AND
PERICARP OF THE PEACH (PRUNUS PERSIC A, SIEB. Z U C C .) AS R E L A T E D
TO F R U IT THINNING WITH PLANT REGULATORS

By

PORTER BRONSON LOMBARD

A THESIS
S ub m itted to the School for A dvanced G ra d u a te Studies of M ich ig an
State U n iv e rsity of A g r ic u ltu r e and Applied S cien ce
in p a r t i a l fu lfillm en t of the r e q u i r e m e n t s
fo r the d e g re e of

DOCTOR OF PHILOSOPHY

D e p a r tm e n t of H o r tic u ltu r e
1958

ProQ uest Number: 10008547

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ACKNOW LEDGEMENTS

The a u th o r d e s i r e s to e x p r e s s h is genuine g ra titu d e to Dr. A r th u r
E. M itch ell fo r h is g e n e ro u s help, v alu ab le su g g estio n s, and guidance t h ro u g h ­
out the in v estig atio n .
G ra te fu l ackn ow led gem ent is e x p r e s s e d to D rs. H. B. Tukey S r. ,
C. L. H am n er, L. W. M e ric le , G. P. S te in b a u e r and F. G. T e u b n e r, fo r
t h e i r g e n e ro u s help and ad v ice in the dev elop m en t of th is study.
The a u th o r w is h e s to e x p r e s s h is deep a p p r e c ia tio n to his wife,
M r s . L o rn a L. L o m b ard , fo r h e r a s s i s t a n c e in the field and la b o ra to ry , fo r
typing of the m a n u s c rip t, and fo r h e r continued e n c o u ra g e m e n t.

TABLE OF CONTENTS
Page
IN T R O D U C T IO N ..................................................................................................

1

REVIEW OF L I T E R A T U R E ...........................................................................

4

C h em ical T h inn in g of F r u i t .............................................................

4

N a tu ra l A b s c is s io n of Young F r u i t ...............................................

7

Seed and F r u i t D e v e l o p m e n t .............................................................

11

S u gg ested M e c h a n is m s fo r F r u i t Thinning w ith N aphthalene a c e tic A c i d ....................................................................................
H orm on e P ro d u ctio n D u rin g Seed and F r u it D evelopm ent.

17

.

22

M ATERIALS AND M E T H O D S .........................................................................

25

I. F ie ld Studies on C h em ical T hinning of P e a c h e s u s in g
N a p h th a le n e a c e tic Acid, N -l-n a p h th y lp h th a la m ic
Acid and 3 - c h lo ro I P C .............................................................

25

II. F ie ld S tudies C o m p a rin g N a tu ra l Blossom and F r u i t Drop
with th at R e s u ltin g fro m the use of N a p h th alen eacetic
Acid and N -l-n a p h th y lp h th a la m ic A c i d ..............................
III.

28

A n a to m ic a l In v e stig a tio n s of the D eveloping E m b ry o and
E n d o s p e rm of H alehaven and Redhaven P e a c h . . . .

30

IV. N a tu ra l H o rm o n e Content and C o n c e n tra tio n of Young R e d ­
haven P each S eeds a s R e la te d to E a r l y G row th and
D e v e l o p m e n t ...............................................................................

.

34

TABLE OF CONTENTS CO NT’D
Page
R E S U L T S ................................................................................................................

38

I. F ie ld S tudies on C h em ical T hinning of P each es u s in g N a p h ­
th a le n e a c e tic Acid, N -l-n a p h th y lp h th a la m ic Acid, and
3 - c h lo ro I P C ....................................................................................

38

II. F ie ld Studies C o m p arin g N a tu ra l Blossom and F r u i t Drop
with th at R e s u ltin g fro m the u se of N a p h th a le n e a c e tic
Acid and N -l-n a p h th y lp h th a la m ic A c i d ...............................

49

III. A n ato m ical In v e stig a tio n s of the D eveloping E m b ry o and
E n d o s p e rm of H alehav en and R edhaven P each . . . .

55

IV. N a tu ra l H orm one Content and C o n c e n tra tio n of Young R e d ­
haven P each S eeds a s R e la te d to E a r l y G row th and D e ­
v elop m en t .........................................................................................

70

DISCU SSION...................................................

80

SU M M A R Y ...................................................................................................................

93

L IT E R A T U R E C I T E D ...........................................................................................

98

1.

INTRODUCTION

Blossom and f ru it thinning is a n e c e s s ity in c o m m e r c i a l p e a c h g r o w ­
ing, a s o v e r p ro d u c tiv ity is com m on fo r the p e a c h t r e e .

Since th is m eth o d of

thinning p r e s e n t s a m e a n s of e lim in a tin g an e x p en siv e p r o c e d u r e of r e m o v in g
p a r t of the b lo s s o m s and young f ru it w ith hand lab o r, m an y in v e stig a tio n s of
c h e m ic a l thinning of p e a c h e s have b een s tim u la te d .

T hus f a r the r e s u l t s of

th e s e stu d ie s have b een c o n tr a d ic to ry p r i m a r i l y b e c a u se of the e r r a t i c r e s p o n s e
of p e a c h t r e e s to the c h e m ic a l thinning tr e a t m e n ts .
T he p la n t r e g u la to r, n a p h th a le n e a c e tic a c id (NAA), u s e d s u c c e s s ­
fully fo r thinning a p p le s when ap p lied a s a f o lia r s p ra y d u rin g and s h o rtly a f te r
bloom , w as found to r e s u l t in effectiv e thinning of p e a c h e s at low c o n c e n t r a ­
tio n s when it w as ap p lied 30 to 42 days a f t e r bloom (33, 44).

C e r ta in i n v e s t i ­

g a t o r s have a ttrib u te d its fa ilu r e to r e d u c e the fru it s e t of p e a c h e s when
a p p lie d s h o rtly a f t e r bloom to la c k of a b s o rp tio n of the th inn in g ag en t b e c a u s e
of the lim ite d le a f s u r f a c e of the t r e e s (6).

M u rn eek (74) b e lie v e d th a t the

p e a c h e m b ry o w hich p la y s a functional r o le in thinning, w as r e s i s t a n t to in h ib ­
itio n by NAA d u rin g its in activ e stag e im m e d ia te ly a f t e r f e r tiliz a tio n .
T he induction of em b ry o a b o rtio n a p p e a r e d to M u rn e e k and T e u b n e r
(76) and Luckw ill (62) a s the m e c h a n is m actio n in which thinning of a p p le s w as
a c c o m p lis h e d w ith p o s t-b lo o m a p p lic a tio n s of NAA.

T he e m b ry o of the apple

2.

is in a v e r y e l e m e n ta r y stag e of developm ent, 8- to 1 6 -celled , .two w eek s
a f t e r full bloom .

T h is h as been found to be one of the m o s t s e n s itiv e p e r io d s

fo r thinn ing a p p le s with NAA (96).

T ukey and Young (102) s ta te d th a t the

e a r l y g row th and dev elo p m en t of the p e a c h e m b ry o a p p e a r e d to take p la c e
m o r e slowly than th at of the apple.

T h is could acco un t fo r the in e f fe c tiv e ­

n e s s of NAA a s a thinning ag en t fo r p e a c h e s when a p p lied c lo s e to bloom .
If the co ncept of e m b ry o a b o rtio n is e n tir e ly acco u n tab le a s a c a u s e
of f r u it thinning, the e a r ly develo pm ent of the p e a c h e m b ry o should be m o r e
c lo s e ly in v e s tig a te d in an a tte m p t to r e c o g n iz e what m a y a cco u n t fo r the late
p e r i o d of s e n s itiv ity of p e a c h e s to NAA a s a thinning agent in c o n t r a s t to the
e a r l y p e r i o d of s e n s itiv ity fo r the apple.
A n o th er p lan t r e g u la to r , N - l-n a p h th y lp h th a la m ic a c id (NPA) h as
been found to e ffectiv ely r e d u c e b lo sso m s e t of p e a c h t r e e s , if ap p lied w ith ­
in a s e v e n -d a y p e r io d im m e d ia te ly a f t e r full bloom (29).

T h e r e f o r e , the

th in ning a c tio n of NPA a p p e a r s to be of a d iffe re n t n a tu r e than th at of NAA.
C o n tr a r y to NAA, the thinning actio n of NPA is r e l a te d to the e a r l y d e v e lo p ­
m e n t of the p e a c h flow er and its com ponent p a r t s .
B ecause of the v a ry in g r e s u l t s r e p o r t e d on c h e m ic a l thin nin g of
p e a c h e s , and the a p p a r e n t v a r ia tio n in tim e of a p p lic a tio n fo r the d iffe re n t
c h e m ic a ls r e s u l t in g in e ffectiv e thinning, a study w as u n d e rta k e n w ith the
follow ing o b je c tiv e s in m ind:

(1) to d e te r m in e the tim e of ap plication ,

c o n c e n tra tio n , and e ffe c ts of NPA, NAA and 3 - c h lo ro IPC fo r effectiv e c h e m i ­
cal thin n in g of p e a c h e s , (2) to c o m p a r e the n a tu r a l drop of p e a c h b lo s s o m s
and f r u i t s to the d r o p s fro m NPA and NAA t r e a t e d t r e e s to d e te r m in e the
r e a s o n fo r the drop, (3) to r e l a t e the d ev elop m ent of the em b ry o , e n d o s p e rm ,
and p e r i c a r p of the p e a c h w ith the tim e of a p p lic a tio n of the p la n t r e g u la t o r s ,
NPA and NAA, fo r m o r e e ffectiv e thinning, and (4) to d e te r m in e the r e l a ­
tive c o n c e n tr a tio n and con ten t of n a tu r a l h o rm o n e s o c c u r r i n g in p e a c h s e e d s
f o r the p e r io d fo ur w eek s a f t e r bloom th ro u g h "June" drop.

LIT ER A TU R E REVIEW

C h e m ic a l T hinning of F r u i t
C h em ical thinning a s r e l a t e d to t r e e f r u its r e s u l t s in the r e m o v a l of
a p o rtio n of the flo w e rs o r f r u its by the ap p licatio n of a c h e m ic a l d u rin g o r
a f t e r bloom to i n c r e a s e the s iz e of the fru it at h a r v e s t tim e and to r e d u c e
annual b e a rin g .

The m a t e r i a l s u sed can be divided into two c l a s s e s , " c a u s t i c ”

c h e m ic a ls and p la n t r e g u l a to r com pounds.
W orking with a d in itro s p ra y a s a " c a u s tic " m a t e r ia l in 1933, A u c h te r
and R o b e r ts (3) found it p o s s ib le to re d u c e the b lo sso m s e t of apple t r e e s w ith ­
out undue in ju ry to the tr e e .

W atson (105) showed that the d in itro com pounds

re d u c e s e t by in ju rin g the sty le of the p is ti l p re v e n tin g p o s s ib le fe rtiliz a tio n .
Since the r e p o r t of A u c h te r and R o b e rts (3, 4), m any p a p e r s have been p r e ­
se n te d on the u s e of c a u s tic c h e m ic a ls fo r b lo sso m thinning of t r e e f r u i t s and
Batj e r and Hoffman (6) have m ad e an e x c e lle n t re v ie w of th e s e p r e s e n t a t i o n s .
B ecause of the r e q u i r e d c r i t i c a l tim in g of d in itro s p r a y s and the
e r r a t i c r e s u l t s fro m t h e i r use, c o n s id e ra b le a tte n tio n h as b een fo c u se d on
p la n t r e g u l a to r m a t e r i a l s fo r thinning fru it.
In 1941 B u rkh old er and McCown (15) r e p o r t e d th at n a p h th a le n e ­
a c e tic a c id (NAA) would re d u c e f r u it set when ap p lied as a s p r a y to apple
t r e e s in full bloom .

T h is w as s u b sta n tia te d s h o rtly a f t e r w a r d by S c h n e id e r

and E n z ie (84, 85), and G r e e n e (31).

5.

D evelop m ent of p o s t bloom thinning began w ith a r e p o r t by D avidson
et a l. in 1945 (22).

Stebbins, Neal and G a r d n e r (91) c o n firm e d th e s e r e s u l t s

u s in g n a p h th a le n e a c e tic a c id (NAA) effectiv ely fro m p e ta l - f a ll to two w eeks
a f t e r p e ta l- f a ll.
A n u m b e r of in v e stig a tio n s followed which w e r e c o n c e rn e d w ith the
tim e of a p p lic a tio n and c o n c e n tra tio n of NAA fo r the v a r io u s apple v a r i e t i e s
(1, 6, 23, 24, 25, 34, 35, 60, 62, 72, 74, 88, 89, 90).
M u rn e e k (74) s ta te d th at the ra n g e of NAA c o n c e n tra tio n fo r f r u it
thinn in g of a p p le s in M is s o u r i w as betw een 10 and 30 ppm depending upon the
v a r i e t y and the tim e of ap p licatio n .

B atjer (6) in W ashington, and Luckw ill

(60) in England, found that e a r l i e r the a p p lic a tio n s of NAA i n c r e a s e d the e f ­
f e c tiv e n e s s of any sing le c o n c e n tra tio n in p o s t-b lo o m thinning of a p p le s .
L uckw ill (62), though, found th at the g r e a t e s t thinning effect o btained fro m NAA
on C ra w le y Beauty w as a t the tim e the e n d o s p e rm ch an g es fro m the f r e e n u c le a r condition to the c e l l u l a r stag e.
NAA w as the f i r s t p la n t grow th r e g u l a t o r s u g g e ste d a s a p o s s ib le
th inn in g ag en t f o r p e a c h e s .

Southwick,

E d g e rto n and Hoffman (87) r e p o r t e d

little s u c c e s s in re d u c in g the f r u it s e t on Golden Jubilee,

E lb e r ta and V alian t

in 1947 w ith e i t h e r the sodium s a lt o r the m ethy l e s t e r of n a p h th a le n e a c e tic
a c id at c o n c e n tr a tio n s of 10 to 40 ppm .

The a p p lic a tio n s w e r e m ad e d u rin g

the p e r i o d of full bloom to 20 days a f te r bloom.

M u rn e e k and H ib b a rd (75)

6.

a ls o r e p o r t e d u n s u c c e s s fu l thinning of p e a c h e s with NAA at the s a m e c o n ­
c e n t r a ti o n s and p e r io d of app licatio n.
T h r e e y e a r s la te r , H ibb ard and M u rn e e k (33) found that NAA ap p lied
35 days a f te r full bloom on E l b e r t a a t 40 to 60 ppm, sig n ific a n tly re d u c e d
f r u it set.

T h e ir ex p lan atio n of the sig n ifican t thinning w as that the e m b ry o

is r e s i s t a n t to inhibition by NAA d u rin g its in activ e stag e .

They im p lie d

th a t the a p p lic a tio n m u s t be m ade a f te r the inactiv e sta g e to be effectiv e.
B atjer and Hoffm an (6) r e p o r t e d fa v o ra b le p e a c h thinning w ith 10
to 30 ppm of NAA ap p lied 30 days a f t e r full bloom when e a r l i e r a p p lic a tio n s
w e r e found to be u n s u c c e s s fu l They a ttrib u te d the ineffectiv e thinning w ith
NAA when ap p lied s h o rtly a f t e r bloom to the lim ite d le a f s u rf a c e fo r a b s o r p ­
tion of the thinning agent.
K elley (40, 41, 42, 44) a ls o r e p o r t e d fa v o rab le p e a c h thinning w ith NAA
when ap p lied two w eek s a f te r " sh u c k -o ff” , about 42 days a f te r full bloom .
F ro m e x p e rie n c e , he found th a t the date of the " sh u c k -o ff" stag e w as m u ch
b e tte r th an full bloom fo r c a lc u la tin g the optim um tim e of a p p lic a tio n (44).
A seco n d m a te r ia l, 3 - c h lo ro - is o p r o p y l- N - p h e n y l c a r b a m a te ( 3 -c h lo ro
IPC) w as r e p o r t e d by M a rth and Prince in 1953 (66) a s an effective thinning
ag en t of p e a c h e s when u s e d at c o n c e n tra tio n s of 200 to 500 ppm 30 and 42 days
a f t e r full bloom .

They a ls o r e p o r t e d th at t r e a t e d f r u i ts m a t u r e d e a r l i e r and

w e r e s o f t e r than th o se not t r e a te d .

And, no foliage in ju ry o c c u r r e d fro m the

7.

u s e of 3 - c h lo ro IPC w hich w as not tru e fo r n a p h th a le n e a c e tic acid.

K elley

(41) o b s e rv e d effectiv e thinning with 3 - c h lo ro IPC ap p lied two w eek s a f t e r
" s h u c k - o f f ” , 42 days a f t e r full bloom, at 200 ppm on E lb e r t a and a t 400 ppm
on H alehaven, but e x te n s iv e fru it in ju ry r e s u lte d .

H o rs fa ll and M o o re (36)

found s a ti s f a c t o r y thinning of H alehaven with 3 - c h lo ro IPC at 200 to 300 ppm
a p p lie d 35 to 48 days a f t e r full bloom, and of E lb e r ta a t 300 ppm ap p lied 38
to 40 days a f t e r full bloom.

In all c a s e s hand thinning had to s u p p le m e n t the

c h e m ic a l thinning, but no f r u it in ju ry w as r e p o rte d .
R ecently, E d g e rto n and Hoffman (29) try in g v a r io u s grow th r e g u ­
la tin g c h e m ic a ls r e p o r t e d thinning of Redhaven, Halehaven, E lb e r ta and July
E l b e r t a w ith N - l- n a p h th y lp h th a la m ic a c id (NPA).

T h is m a t e r i a l w as found

to be m o s t effectiv e when u sed a p p ro x im a te ly t h r e e days a f t e r full bloom .
They s u g g e ste d a c o n c e n tra tio n ran g e of 150 to 400 ppm depending on the v a r ie ty .
B urkholder and A r m s tr o n g (14) u sin g th is sa m e m a t e r ia l had r e s u l t s v a r y in g
fro m no thinning to fa v o ra b le thinning, to o v e r-th in n in g .

W estwood (106)

s u c c e s s fu lly u se d NPA a t 200 and 300 ppm one w eek a f t e r full bloom on E l b e r t a
and R edhaven.

W estwood fa v o re d the l a t e r ap p licatio n in o r d e r to e lim in a te

the d a n g e r of thinning b efo re a p o s s ib le la te killing f r o s t.

N a tu ra l A b s c is s io n of Young F r u i t
Many i n v e s tig a to r s have stu d ied the o c c u r r e n c e of n a tu r a l f r u it drop
w hich ta k e s p la c e e a r l y in the gro w in g s e a so n .

T h is drop a p p e a r s to be c lo s e ly

a s s o c i a te d with the r e m o v a l of flo w e rs and young fru it by the a p p lic a tio n of
v a r io u s thinning c h e m ic a ls .
A b s c is s io n of ap ple f r u it s e a r l y in the grow ing s e a s o n a s d e s c r ib e d
by How lett (37) ta k e s p la c e a s two p r i m a r y ' ’d ro p s" .

He c o n s id e re d th a t the

f i r s t drop u s u a lly c o n s is te d of "u n e n la rg e d " flo w e rs and " e n la rg e d " flo w ers,
while the secon d drop c o n s is te d of only the l a t t e r .

M u rn eek (71) p o in ted out

th a t a b s c i s s io n of young apple f r u it s c o n s is te d of four p e r io d ic " w av es".
f i r s t drop w as a c tu a lly two o v e r -la p p in g "w av es".
of a b n o r m a l and of u np ollinated flo w e rs .

The

The f i r s t one c o n s is te d

T his drop a lso included p o llin a te d

flo w e rs when f e r tiliz a tio n had fa ile d to tak e p la c e .

The seco nd "w av e" c o n ­

s is t e d of flo w e rs in which the to r u s had e n la rg e d .

The second drop o r "June"

drop M u rn e e k divided into th ir d and fo urth a b s c is s io n "w av e” although the
ev id en ce fo r th is div isio n w as not too s tro n g .

The l a s t two "w av es" of f r u it

a b s c is s io n , he poin ted out, c o n s is te d of f r u it w h e re f e r tiliz a tio n w as follow ed
im m e d ia te ly by e m b ry o a b o rtio n .
D etjen (26) s u g g e ste d only two p e r io d s of drop follow ing bloom fo r
peach tre e s.

T he f i r s t drop s h o rtly a f te r bloom c o n s is te d p r i m a r i l y of d e v e l­

oping p i s t i l s , but m ay co n tain so m e f r u its w ith a b o r te d p i s t i l s and w ith " u n d e ­
v elo p ed " p i s t i l s .

The "June" drop, the second p erio d , he stated , c o n s is te d

e n t i r e ly of fru it w ith developing e m b ry o s .
w a s m u c h h e a v ie r than the f i r s t.

T he "June" drop, he d e s c rib e d ,

9.

B radb ury (7) found th r e e p e r i o d s of a b s c i s s e d im m a t u r e c h e r r y f r u it
follow ing the in itia l drop of ’’undeveloped" p i s t il s .

She found s o m e u n p o llin ated

f lo w e rs d ro p p in g a s la te a s two and o n e - h a lf w eeks a f t e r bloom .

She o b s e r v e d

a d e g e n e r a tio n of the e m b ry o s a c of the a b s c i s s in g f r u its c a u s e d by in c o m p a ti­
b ility of g a m e te s w ith f ru it drop r e a c h in g a p e a k t h r e e and o n e - h a lf w eek s a f t e r
bloom .

" D ro p s " fro m the th i r d p e r io d o c c u r r i n g six and o n e -h a lf w eek s a f t e r

bloom , c o n s is te d of f r u i t s w ith d e g e n e r a te d e m b r y o s a n d / o r e n d o s p e r m s .
T he c a u s e of young f r u it a b s c i s s io n a c c o r d in g to H owlett (37) and
B rad b u ry (7) a p p e a r s to be n u tritio n a l c o m p etitio n .

H ow ever, D etjen (26)

and D etjen an d G r a y (27) c o n s id e r e d g en etic f a c t o r s of g r e a t e r im p o rta n c e
th a n the e n v iro n m e n ta l one of n u tritio n .

K ra u s (46) o b s e r v e d th at the e a r l i e s t

d r o p s of i m m a tu r e ap p les, w hich fell s h o rtly a f t e r the a b s c i s s io n of f e r t i l iz e d
flo w e rs , show ed sligh t o v u la r developm ent, but w ith evid ence of l e s s e n d o ­
s p e r m and e m b ry o d evelo pm ent in th o se ov ules a s c o m p a r e d to th o se in the
f r u i t r e m a i n in g on the t r e e .

D etjen (26) and M u rn e e k (71) s t r e s s e d th at e m b ry o

a b o r tio n w as p r i m a r i l y r e s p o n s ib le fo r the a b s c i s s io n of the i m m a t u r e f r u i t s
of the ’’June” drop.

B ryant (13) m a k in g a study of the f a c t o r s a ffe c tin g e m b r y o s

in the M cIntosh, s ta te d "T he v ig o r of the apple e m b r y o s r e s u l t i n g fro m e f f e c ­
tiv e p o llin a tio n co ntinu ed to be m a n ife s te d in e n d o s p e rm dev elop m en t. "
Studying the C a r m a n v a r i e ty of peach, H a r r o l d (32) o b s e r v e d th at the
zy go te n u cleu s divided 12 days a f t e r bloom .

T h is w as p r e c e d e d by the f i r s t

10.

e n d o s p e rm n u cleu s d iv isio n by two o r th r e e days.

The e n d o s p e rm r e m a in e d

in a f r e e - n u c l e a r s ta te until the end of the sixth w eek.

He a g r e e d w ith B rad b ury

(7) in o b s e r v in g t h r e e p e r i o d s of f r u i t drop, the f i r s t d u rin g a t h r e e - w e e k
p e r i o d beginning one to t h r e e days b efo re bloom, the s e c o n d la s tin g a p e r io d
of sev en days at five w eek s a f t e r bloom , and the th i r d d u rin g a s e v e n -d a y
p e r i o d about the se v e n th w eek a f t e r bloom .

T h e d ro p s of the f i r s t p e r i o d c o n ­

s is te d m o s tly of f r u i ts w ith o vules which d e g e n e r a te d b etw een the m e g a s p o r e
m o t h e r c e ll sta g e and the e a r l y m e g a g a m e to p h y te stag e .

T he o v u les of o th e r

f r u i t s in th is g roup gave ev id en ce th a t f e r t i li z a t i o n had ta k e n p la c e .

The

d ro p p e d f r u i t s of the seco n d and t h i r d p e r io d s w e r e found to have o v u les in
w hich the n u cellu s, e n d o s p e rm , and e m b ry o lack ed n o rm a l dev elo pm ent, a s
m e a s u r e d by s iz e .

The only s t r u c t u r a l d iffe re n c e he could o b s e r v e betw een

the d eveloping f r u it and the a b s c i s s e d f r u it w as the d e g e n e ra tio n of the n u c e llu s
in the c h a la z a l r e g io n of the a b s c i s s e d fru it.

F r o m th is o b s e r v a tio n he b e ­

lieved th a t such d i s o r d e r in the c h a la z a l r e g io n would d i s a r r a n g e the v a s c u l a r
s y s te m and m ig h t c a u s e d is in te g r a tio n of the e n d o s p e rm and a b o r tio n of the
e m b ry o b e c a u s e of the f a ilu r e of food conduction.
D o r s e y (28) found th at the f i r s t d iv isio n of the e n d o s p e rm in E l b e r t a
p e a c h e s o c c u r r e d about 20 days a f t e r full bloom, and in the zyg ote a w eek la t e r .
The e m b ry o had r e a c h e d only a s ix - to e ig h t- c e lle d sta g e a s late a s 40 days
a f t e r full bloom .

F o r the J. H. Hale, a v a r i e ty in w hich r e t a r d e d f r u i t s o r

"b u tto n s" a r e com m on, he found the d evelo pm ent of the e m b ry o and e n d o s p e rm
g r e a t l y r e t a r d e d a s c o m p a r e d to the E lb e r ta .

He b eliev ed th a t " sin g le f e r t i l i ­

z a tio n " , r e f e r r i n g to a sing le g a m e te fusio n of e ith e r the egg o r the e n d o s p e rm
n u cleu s, w as the m o s t p ro b a b le c a u s e of th is condition.

F ro m th is he i n f e r r e d

th at e m b ry o and e n d o s p e rm d ev elo p m en t a r e in te rd e p e n d e n t.
T uk ey (100, 101) by a r t i f i c i a l l y d e s tr o y in g c h e r r y and p e a c h e m b r y o s
a t v a r i o u s p e r io d s of growth, d e m o n s tr a te d th a t the e m b ry o h as a definite
b e a r i n g on fru it fo rm a tio n .

D e s tru c tio n of the e m b ry o e a r l y in the d ev elo p m en t

of the fru it, d u rin g the a r r e s t e d p e r i c a r p dev elo p m en t o r e a r l i e r , r e s u l t e d in
a b ru p t ch eck in f r u it growth, and eventu al a b s c is s io n of the fru it.

D e s tru c tio n

of the e m b ry o a f t e r th is stag e did not influence f r u it dev elop m en t.

Seed and F r u i t D ev elo pm en t
M any in v e s tig a to r s have stu died the d ev elo p m en t of the e m b ry o and
e n d o s p e rm in r e la tio n to the d ev elo p m en t of the pom e and stone f r u its .

How­

e v e r, t h e r e is s till in fo rm a tio n to be d eriv ed .

M a h e sh w a ri (65) s ta te d th a t

a f t e r f e r t il i z a t i o n the zygote r e m a i n s inactive.

The d u ra tio n of in a c tiv ity

depends on the s p e c ie s and e n v iro n m e n ta l cond itio ns.

T he f i r s t d iv isio n of

the zyg ote is followed a lm o s t alw ays by the f o rm a tio n of a t r a n s v e r s e wall,
f o r m in g a t e r m i n a l c e ll a t the i n t e r i o r side of the e m b ry o s ac and b a s a l c e ll
a t the e x t e r i o r side.

Six p r in c ip a l ty p es of e m b r y o s am o n g D icoty led on s have

b een r e c o g n iz e d by Joh ansen (39) b a s e d on w h e th e r the t e r m i n a l cell d ivid es

12.

lo n g itu d in ally o r t r a n s v e r s e l y and on the c o n trib u tio n of the b a s a l c e ll to the
d ev elo p in g e m b ry o .

T h e s e six e m b ry o ty p es a r e P ip e ra d , O nagrad, A s te ra d ,

Solanad, C ry o p h y llad and Chenopodiad.
T e u b n e r and M u rn e e k (96) s ta te d that the apple e m b ry o can be c lo s e ly
c o m p a r e d to that of Geum u rbanu m w hich h a s been c l a s s i f ie d by M a h e sh w a ri
(65) a s an A s t e r a d type.

T h e r e w as a sing le t r a n s v e r s e d iv isio n in th is zygote

w hich w as followed by an oblique d iv isio n in the t e r m i n a l cell and a seco n d
t r a n s v e r s e d iv isio n in the b a s a l cell.
In c o n t r a s t to the findings of T e u b n e r and M u rn eek (96), M e y e r (67)
o b s e r v e d th at the d is til ce ll of the f o u r - c e l l e d e m b ry o of the M cIntosh apple
w hich is fo rm e d fro m a t r a n s v e r s e div isio n of the d ista l cell of the tw o -c e lle d
em b ry o , p r o d u c e s all the t i e r s of the e m b ry o p r o p e r .

He s u g g e ste d th at the

apple e m b ry o dev elo p m en t w as of the Solanad type fro m Johansen*s (39) c l a s ­
sificatio n .

The e m b ry o of the p e a c h h a s not been c l a s s i f ie d a s to type.

M e y e r (67) stu dy ing the e a r l y d ev elop m en t of the M cIntosh e m b ry o
fro m the zygote to the beginning of the c o ty le d o n a ry stag e, p r o p o s e d th r e e
s ta g e s b a s e d on the b ro a d p a t t e r n s of m e r i s t e m a t i c a ctiv ity .

The f ir s t, the

" fila m e n to u s " stag e, began w ith the zygote and continued a s long a s, a c c o r d in g
to M ey er,

"T he e m b ry o g ro w s and d ivid es a s a l in e a r ob ject. " The " s p h e r i c a l ’1

stage, the second, began when the d is ta l t i e r s of c e lls i n c r e a s e in s iz e in t h r e e
d im e n s io n s .

The th ird , the " tr a n s i ti o n a l " stage, w as m a r k e d by a change in

the d is tr ib u tio n of grow th, giving a t r ia n g le a p p e a r a n c e to the e m b ry o , and
c lo s e d when the two c o ty le d o n a ry p r im o r d i a p r o tr u d e fro m the s u r f a c e of the
e m b ry o .
M a h e s h w a r i (65) s ta te d th a t in m o s t c a s e s the f i r s t d iv isio n of the
p r i m a r y e n d o s p e rm p r e c e d e s the f i r s t zygote divisio n.

T h r e e ty p es of e n d o ­

s p e r m dev elo p m en t w e r e r e c o g n iz e d by M a h e sh w a ri a s n u c le a r, c e llu la r , o r
h elo b ial.
P e c h o u tre (81), O s t e r w a ld e r (79), T u key (97), and Luckw ill (56)
have found the e n d o s p e rm d ev elo p m en t of the apple and stone f r u i ts to be
n u c le a r .

In the n u c le a r type, the f i r s t div isio n and a few of the su b seq u en t

d iv isio n s do not fo rm w alls, but the nu clei m a y e i t h e r r e m a i n f r e e o r in l a t e r
s ta g e s b e c o m e s e p a r a te d by w a lls.

As Brink and C oo per (10) have an e x c e lle n t

re v ie w of e m b ry o and e n d o s p e rm d ev elop m ent in d ic o ty le d o n a ry p la n ts, only
the l i t e r a t u r e r e l a t iv e to the d ev elo p m en t of the com ponent p a r t s of th e p e a c h
s e e d w ill be d is c u s s e d h e r e .
O s te r w a ld e r (79) r e p o r t e d th a t the f i r s t ce ll div isio n in the zygote
of h a n d -p o llin a te d ap p le flo w e rs o c c u r r e d nine days a f t e r po llin atio n .

T h is,

he stated , w as follow ed by a p e r io d of r a p i d grow th 12 to 16 days a f t e r full
bloom when the e m b ry o w as in the f o u r- to e ig h t- c e ll stag e .

Knight (45) c o n ­

f i r m e d the o b s e r v a tio n s of O s t e r w a l d e r of the e a r l y s ta g e s of e m b ry o d e v e lo p ­
m en t.
F r o m O s te rw a ld e r* s findings (79) the d iv isio n of the e n d o s p e rm

14.

n u c le u s p r e c e d e d th a t of the zygote.

He showed th at one of the f i r s t two e n d o ­

s p e r m nu clei m i g r a t e d to w a rd the m i c r o p y l a r end of the e m b ry o sac; and, it
w a s fro m th is n u cleu s that the c e l l u l a r e n d o s p e rm w as d e riv e d .

The r e m a i n ­

ing n u c le u s f o r m e d the l a r g e - n u c l e a r e n d o s p e rm in the c h a la z a l re g io n .
O s t e r w a ld e r (79) d e s c r i b e d a ls o the is th m u s of c o n s tr ic tio n w hich divided the
e m b r y o s a c into two r e g io n s .

He found th at the ce ll w a lls of the e n d o s p e rm

w e r e not la id down beyond the is th m u s to w a rd the c h a la z a l re g io n and s u g g e s te d
th a t th is w as due to the c h e m ic a l m a k e -u p and n u tritiv e function of th at reg io n .
P e c h o u tre (81) a p p a r e n tly m ad e the f i r s t o b s e rv a tio n s of e m b ry o d e ­
v e lo p m e n t in the P ru n u s s p e c ie s .

Although the d e ta ils w e r e not defin ite from

a tim e re la tio n s h ip , he im p lie d th at the e m b ry o d ev elop m ent of the P ru n u s
s p e c ie s w as m u ch s lo w e r than the e m b ry o d ev elo p m en t of the apple.
T uk ey (97) found the e m b ry o g en y of P ru n u s avium to be s i m i l a r to
P y ru s m a lu s .

He o b s e rv e d th at the f i r s t d iv isio n of the sw eet c h e r r y zygote

o c c u r r e d about four days a f te r full bloom when it p r o d u c e d a s u s p e n s o r cell.
S u bsequ ence e m b ry o d ev elo p m en t w as v e r y slow until about 24 days a f t e r full
bloom, when a sudden ra p id d evelo pm en t of the e m b ry o ta k e s p la c e .

The

p r i m a r y e n d o s p e rm n u c le u s of the sw eet c h e r r y a s d e s c r ib e d by T ukey (97)
divided p r i o r to the d iv isio n of the zygote.

C ell w a lls began to a p p e a r on the

ninth day a f t e r full bloom at the m i c r o p y la r end of the e m b ry o sac.

C ell w all

f o rm a tio n co ntinued p r o g r e s s i v e l y fro m the m ic r o p y l a r to the c h a la z a l end

and f ro m the p e r i p h e r y in w a rd u ntil it b ecam e a solid m a s s .

He found that

the c h a la z a l r e g io n of the e m b ry o s a c n e v e r b ecam e m u ltic e llu la r .

T he

r a p i d d e v elo p m en t of the c e llu la r e n d o s p e rm of the sw eet c h e r r y c o m m e n c e d
about s e v e n days b e fo re the r a p id d ev elo p m en t of the em b ry o .
T uk ey (98, 99) p r o p o s e d t h r e e s ta g e s of f ru it dev elo p m en t for P ru n u s
p e r s i c a and P ru n u s c e r a s u s .

T he f i r s t stag e (Stage I) w as c h a r a c t e r i z e d by a

p e r i o d of r a p id i n c r e a s e of the p e r i c a r p following f e rtiliz a tio n .

C oinciding

w ith th is w as the r a p id dev elo p m en t of the n u cellu s and in teg u m en ts.

F o r the

p each , Stage I continued fo r about 40 to 50 days d u rin g which the grow th of
th e e m b ry o w as e x t r e m e l y slow.

In Stage II t h e r e w as a m a r k e d d eclin e in

the r a t e of g ro w th of the p e r i c a r p and a c e s s a tio n of grow th of the n u cellu s
and in te g u m e n ts.

He found that the em b ry o c o m m e n c e d to grow ra p id ly at

th e b eg in nin g of Stage II and r e a c h e d m a x im a l s iz e by the end of Stage II.
e n d o c a rp began to h a r d e n d u rin g th is stag e .

The

It w as su g g e ste d by T u key (97),

H a r r o ld (32), and Luckw ill (57) th a t the in itia tio n of th is p e r io d of r a p id e m b ry o
d ev elo p m en t in both the stone f r u it s and the apple m ay coincide w ith the change
of the e n d o s p e rm fro m a f r e e - n u c l e a r to a c e l l u la r sta te .

The beginning of

Stage III w as co in cid en t with the second ra p id i n c r e a s e in r a te of grow th of
the p e r i c a r p , and continued until the fru it w as m a tu re .

Tukey (98) found th at

in e a r l y r ip e n in g v a r i e t i e s of p e a c h e s Stage III began when the e m b ry o was
in a p e r io d of r a p id growth, which, in tu rn , s o m e tim e s c a u s e d e m b ry o a b o rtio n .
O th e r in v e s tig a to r s who have e m p h a s iz e d the t h r e e definite s ta g e s of

16.

g ro w th fo r the stone f r u i t s a r e C o nn ors (16), L ille la n d (48), L ott (52, 53),
H a r r o l d (32), and L o tt and A sh ley (54) on p e a c h e s ; L ille la n d (46, 50) on
a p r ic o ts ; L ille la n d and N ew som e (51) on c h e r r i e s ; L ille la n d (49) on p lu m s;
and Brooks (12) on a lm o n d s.
T ukey and Young (102) s u g g e ste d a s i m i l a r p e r io d ic ity in the grow th
of the ap p le in d icatin g that the c a r p e l of the apple developed s im i l a r ly to the
p e r i c a r p of the P ru n u s f ru its .

They found th at the c a r p e l b lad es and the n u cellu s

and in te g u m e n ts r e a c h e d full length e a r l y in the d evelop m ent of the fru it, while
the e m b ry o r e m a in e d m i c r o s c o p i c fo r som e tim e a f t e r full bloom.

H owever,

unlike the e m b ry o of P r u n u s , the e m b ry o of the apple began r a p id d ev elo p m en t
b e fo re the n u c e llu s and in te g u m e n ts and the c a r p e l blade have h e ach ed m a x i ­
m um length.

T hey b e lie v e d th a t t h e r e w as g r e a t e r s i m i l a r i t y betw een the

d ev elo p m en t of the em b ryo ,

n u c e llu s and in teg u m en ts, and the c a r p e l of the

apple and of the P ru n u s f r u i t s than t h e i r findings r e v e a le d .
M itc h e ll (68) found a c lo s e s im i l a r i t y in fru it develop m ent betw een
the p e a r and the drupe f r u i ts .

He n oted that the e n la r g e m e n t on the e n ti r e

f r u it of the B a rtle tt p e a r w as v e r y r a p id ju st a f t e r full bloom and la s te d up to
eig ht w e e k s when grow th d eclin ed n oticeab ly.

He r e p o r t e d that the n u c e llu s and

in te g u m e n ts a c q u ir e d a lm o s t t h e i r full length d u rin g th is e a r l y p e r io d of ra p id
f r u it grow th, w hile the e m b ry o r e m a in e d m ic ro s c o p ic .

R e la te d to the d ecline

of f r u it g row th eigh t w eeks a f t e r full bloom w as the r a p id i n c r e a s e in length

of the e m b ry o w hich r e a c h e d its m ax im u m s iz e about fo u r w eek s l a te r .
R e s u m p tio n of r a p id g ro w th of the e n tir e p e a r f r u it 10 w eeks a f t e r full bloom
w as found to be r e l a te d to a d eclin e in e m b ry o dev elo pm en t.
As r e p o r t e d by Tukey and Young (102) and M itc h e ll (68), the e a r l y
d e v elo p m en t of the c o r te x of the apple and the e n la r g e m e n t of the c a r p e l, pith,
and c o r te x of the p e a r , involved an a p p r e c ia b le am ount of g row th by both c e ll
d iv isio n and cell e n la r g e m e n t.

H ow ever, cell d iv isio n c e a s e d at about the

tim e of r a p id e m b ry o develop m ent.

By c o n tr a s t, cell d iv isio n in the flesh y

p e r i c a r p of the s o u r c h e r r y (99) and of the c lin g p e a c h (5) did not c e a s e until
about the f i r s t half of Stage II, d u rin g r a p id e m b ry o developm ent.

F ru it en ­

la r g e m e n t of the apple, p e a r , and stone f r u its a f t e r the p e r io d of ra p id
e m b ry o grow th w as brought about a lm o s t e n tir e ly by ce ll e n la rg e m e n t.

Suggested M e c h a n is m s fo r F r u i t T h inn ing w ith N a p h th a le n e a c e tic Acid
M any in v e stig a tio n s have been conducted r e g a r d in g the p o s s ib le m e c h ­
a n ism by w hich NAA m a y re d u c e f r u i t set.

Van O v erb eek (103) s u g g e ste d fro m

i n d ir e c t e v id en ce th at NAA m a y a c c e l e r a t e a b s c is s io n of young f r u i t s by a c c e l ­
e r a t i n g gro w th in the a b s c i s s io n zone of the p ed icel, which functions in the
d e c o m p o s itio n of the m id d le la m e lla .

T h is condition led even tually to the

m e c h a n ic a l f r a c t u r e of the a b s c i s s io n zone c a u s in g the f ru it to drop.
R ec en tly Luckw ill (62) o b s e rv e d that NAA s p r a y e d on open apple
flo w e rs b e fo re p o llin a tio n induced in c o m p a tib ility betw een p o llen tu b es and

18.

s t y l a r tis s u e , thus a cco u n tin g fo r thinning a c tio n of NAA when a p p lied at
th is stag e .

When NAA w as ap p lied on apple t r e e s d u rin g p o st bloom, an

obvious delay in im m a t u r e fru it d ro p p in g h as been o b s e rv e d by fo u r i n v e s t i ­
g a t o r s (62, 76, 89, 93).

T h e r e f o r e , one of the e ffects of thinn ing s p r a y s of NAA

a p p e a r e d to be a t e m p o r a r y delay of a b s c is s io n fo r one o r two w eeks, which
is s i m i l a r to the effect p ro d u c e d by a p r e h a r v e s t a p p lic a tio n of NAA to p r e ­
vent f r u i t drop (93).

S tru c k m e y e r and R o b e r ts (93) p r o p o s e d a p o s s ib le

m e c h a n is m of NAA thinning a f te r r e c o g n iz in g th is effect.

T h e ir h y p o th e sis

c o n s id e r e d the p la n t r e g u l a t o r thinning of fru it a s an e x te n sio n of i m m a tu r e
f r u i t drop, r e s u lt i n g fro m the n u tritio n a l c o m p etitio n c a u s e d by the t e m p o r ­
a r i l y i n c r e a s e d set.
A fo u rth p o s s ib le m e c h a n is m of f ru it thinning u s in g NAA h as been
p r o p o s e d by M u rn e e k (71, 73) by an ex p lanation of n a tu r a l f ru it drop involving
the functional im p o rta n c e of the e m b ry o as a n a tu r a l s o u rc e of h o rm o n e to
p r e v e n t f r u i t a b s c is s io n .
on ap p les,
ab scissed .

M u rn e e k (73) found that with NAA thinning s p r a y s

la r g e f r u i t s tend ed to r e m a i n on the tre e , w h e r e a s s m a ll f r u its
He b e lie v e d th a t th is w as due to the p r e s e n c e of l a r g e r n u m b e r of

s e e d s in the l a r g e r f r u its with the e m b r y o s supplying the r e q u i r e d am o un t
of h o rm o n e to p r e v e n t f r u it a b s c is s io n .
a b o rtio n in f r u it s s p r a y e d w ith NAA.

He m en tio n ed the o c c u r r e n c e of se e d

Based on this, he s u g g e ste d that NAA

u se d at r e l a t iv e ly high c o n c e n tra tio n s fo r apple and p e a c h thinning m ight

19.

d i s t u r b the e m b ry o a n d / o r e n d o s p e rm d u rin g the c r i t i c a l p e r io d of e a r l y seed
d evelo pm en t.
By r e m o v in g i m m a tu r e f r u i t s fro m the apple tr e e , but leav in g the
p e d ic e l in ta c t w ith the sp u r, M u rn e e k and T e u b n e r (76) found that an a p p l i ­
c a tio n of NAA at 30 ppm, im m e d ia te ly a f t e r the r e m o v a l of the f ru its , d e ­
lay ed the a b s c i s s io n of the p e d ic e ls .

In a n o th e r e x p e rim e n t, a f t e r e x am in in g

a b s c i s s e d f ru it of NAA s p ra y e d t r e e s , they o b s e rv e d e m b r y o s which w e r e
in h ib ited in grow th a s c o m p a r e d w ith th o se in s e e d s of a p p le s which had set
and w e r e developing.

The two in v e s tig a to r s e m p h a s iz e d the c o n tro l in v e ste d

in the e m b ry o on the a b s c is s io n of the p e d ic e l.

F ro m th e s e s e r i e s of e x p e r i ­

m e n ts , M u rn e e k an d T e u b n e r b e lie v e d that the ex tent of fru it th in nin g by NAA
w as p a r t i a l l y dependent upon its t e m p o r a r y p o s itiv e effect on the a b s c is s io n
l a y e r of the p e d ic e l (30) and its s tr o n g n egative effect on the h o rm o n a l f u n c ­
tio n of the em b ry o.
Luckw ill (61) and T e u b n e r and M u rn e e k (76) have added m uch s u p p o rt
to the h y p o th e sis th at NAA in d u c e s e m b ry o ab o rtio n .

The l a t e r found th at the

m o s t s u s c e p tib le s ta g e d u rin g apple e m b ry o developm ent to th is induced a b o r ­
tio n w as w hen the e m b ry o w as in the 8- to 16- c e lle d stag e.

They b eliev ed

the a d d itio n of an exogenous supply of a p lan t r e g u la to r to the a l r e a d y n a tu r a l
h o rm o n e s a tu r a t e d e m b ry o r e s u l t e d in inhibition of th is o rg an .
F u r t h e r e v id en ce that the e m b ry o m a y c o n tro l f ru it a b s c i s s io n a s a

20.

m e c h a n is m of f ru it th inn in g h a s been s u p p o rte d by the " s o m a to p la s tic s te r i l i t y "
th e o ry .

Cooper, Brink and A lb re c h t (8, 9, 17, 18, 19, 20, 21) found m u ch evid en ce

in su p p o rt of th is th eo ry .
" S o m a to p la stic s t e r i l i t y " a s e x p lain ed by Brink and C ooper (8) is the
h y p e r p la s ia of the s o m a tic t i s s u e s of the f e r t il i z e d ovule, such a s the n u cellu s
an d in te g u m e n ts.

O v e r -g r o w th of the n u c e llu s and in te g u m e n ts o c c u r r e d a s

a r e s u l t of a lag in the n o r m a l d ev elo p m en t of the e n d o s p e rm , th e r e b y lead in g
to the d is in te g r a tio n of the e n d o s p e rm .

Subsequently, the em b ry o b e c a m e

d is o r g a n iz e d and ev en tu ally the c o m p le te ovule co llap se d .
T he condition a s found in the a lfalfa ovule a f t e r s e lf - f e r t i l i z a t i o n
f i r s t a p p e a r e d w henconductive t i s s u e s betw een the apex of the v a s c u l a r bundle
and the c h a la z a l p o ck et fail to d iffe re n tia te (8).

Cytoplasm of the n u cellu s

c e lls a d ja c e n t to the e m b ry o s a c b e c a m e fin elly v a c u o la te d and e x ten siv e
m e r i s t e m a t i c a c tiv ity o c c u r r e d a t the c h a la z a l p o rtio n of the in n e r in tegu m ent
d u r in g th is tim e .

A fte r s e lf - f e r t i li z a t i o n of the alfalfa, e n d o s p e rm d i s o r g a n i ­

z a tio n developed, f i r s t at the c h a la z a l end and then p r o g r e s s e d to w ard the
m ic ro p y le .

Subsequently, the c y to p lasm of the c e lls of the e m b ry o b e c a m e

d e n s e and the e m b ry o c o lla p s e d a f t e r the co m p lete d is in te g r a tio n of the e n d o ­
sperm .
T h e s e p h en o m en a w e r e l a t e r found to o c c u r in unfruitfu l in te r s p e c if ic
c r o s s e s of N ico tian a (9).

Brink and C o op er (9) b eliev ed th a t the o v e r - g r o w th

21.

of the m a te r n a l tis s u e a s a f o r e - r u n n e r may, m o re o r l e s s c o m p le te ly o b s tr u c t
the im m e d ia te line of food supply to the e n d o s p e rm .

They e m p h a s iz e d the

n u tr itiv e r o le w hich the e n d o s p e rm p la y s in the d ev elo pm en t of the e m b ry o .
The ” s o m a to p la s tic s t e r i l i t y " th e o ry has been b rou gh t fo rth a ls o a s
a r e a s o n fo r n a tu r a l f r u it drop.

As s ta te d e a r l i e r , H a r r o l d (32) in 1935

b e lie v e d th a t i m m a tu r e fru it drop of p e a c h e s m a y be c a u s e d by the d e g e n e r a ­
tion of the n u c e llu s in the c h a la z a l re g io n th e r e b y a ffectin g e n d o s p e rm d i s ­
i n te g ra tio n and e m b ry o ab o rtio n .

D o rs e y (28) m ade the s a m e o b s e rv a tio n in

1939 a s d e s c r i b e d by Brink and C o op er in 1940 (9) when he s ta te d th at the
g ro w th of the e m b ry o w as dependent on e n d o s p e rm develop m ent in n o r m a l
f r u it of the p e a c h v a r ie t y J. H. Hale.
B ritten in 1947 (11) and T e u b n e r and M u rn e e k in 1955 (96) i n v e s t i ­
g a te d the p o s s ib ility of a p la n t r e g u l a to r function in " s o m a to p la s tic s te r il i t y " .
B ritten (11) found th at a n a p h th a le n e a c e tic acid tr e a tm e n t on the c o rn e a r at
th e tim e of f e r t i li z a t i o n p ro d u c e d a t e m p o r a r y s tim u la tio n of the o v a r i e s for
eigh t to nine days, but lag ged behind the n o rm a l o v a r ie s in d ev elop m en t a f t e r ­
w ards.

T r e a t e d c a r y o p s i s a s c o m p a r e d to th o se r e c e iv in g no t r e a t m e n t w e r e

found to c o n s is t of e n d o s p e rm and e m b ry o r e t a r d e d in d ev elo p m en t when
o b s e r v e d nine days a f t e r tr e a tm e n t.

T he e n d o sp erm of t r e a t e d o v a r ie s at

th is sta g e a p p e a r e d to la c k the a b s o rp tiv e la y e r of c e lls at the b a s e .

Endo­

s p e r m and e m b ry o d is in te g r a tio n w as found to o c c u r in t r e a te d c a r y o p s i s in

12 to 18 d ay s.

Even though a condition a p p ro a c h in g " s o m a to p la s tic s te r i l i ty "

a p p e a re d , B ritten b e lie v e d the r e s e m b l a n c e to th is condition m ay have been
only s u p e rf ic ia l.
Studying the inh ibitio n of e m b ry o dev elo p m en t by n a p h th a le n e a c e tic
acid, T e u b n e r and M u rn e e k (96) w o rk in g with the p e p p e r p la n t o b s e r v e d som e
d e g e n e r a tio n of the en d o s p e rm 12 days a f te r t r e a t m e n t.

E n d o s p e rm and e m b ry o

d e g e n e r a tio n w as p r e s e n t in the o ld e s t in hibited o v u les when e x am in ed 90 days
a f t e r t r e a t m e n t.

The d e g e n e ra tin g e m b ry o s a c s at th is late stage w e r e found

to exhibit a h y p e r p la s ia at the c h a la z a l reg ion .

H o rm o n e P ro d u ctio n D u rin g Seed and F r u it D evelopm ent
T h e r e l e a s e of n a tu r a l h o rm o n e s by the p h y sio lo g ic a l p r o c e s s e s
a s s o c i a t e d w ith f e r tiliz a tio n , a p p e a r s to p lay an im p o rta n t r o le in the g ro w th
a n d d ev elo p m en t of the fru it.
M u rn e e k (70) s u g g e ste d th at the a c tio n of g a m e te union m a y be a
s eco n d s o u rc e of s tim u la tio n to the develop m ent of the f r u it and seed .

W ittw er

(107) w o rk in g w ith c o rn found two p e r io d ic s tim u la tio n s in gro w th a s s o c ia t e d
w ith the p r o c e s s of fe rtiliz a tio n , one o c c u r r e d at the tim e of the s y n a p s is
p h a s e , and the o t h e r a t the tim e of the syngam y p h a s e .

Two m a j o r p e a k s of

h o rm o n e a c c u m u la tio n in the c o r n c a r y o p s i s followed th e s e two p h a s e s .
R ed em ann , W ittw er and Sell (81) have sin ce id en tified th e is h o rm o n e found in
c o r n k e r n e l s a s ethyl in d o le a c e ta te .

23.

In 1942, M u ir (69) w o rk in g with tobacco, N icotiana to b a c u u m , found
l a r g e q u a n titie s of the h o rm o n e in p o llin a te d p i s t i ls , but v e r y little in n o n ­
p o llin a te d p i s t i l s .

He o b s e rv e d no h o rm o n e s in p o llen g r a in s o r p o llen tubes,

but he b e lie v e d the p o llen tu b es m ay have r e l e a s e d an en zym e w hich a c tiv a te d
a h o rm o n e fro m in activ e com pounds in the sty le and p is ti l .

N itsch (77) s tu d y ­

ing the p ro d u c tio n of n a tu r a l h o rm o n e s d u rin g the grow th of the p o llen tube
down the sty le of the s t r a w b e r r y flow er a lso in d icated th at th e s e n a tu ra l h o r ­
m o n e s m a y have acco u n ted fo r the initial s tim u la tio n of fru it d ev elop m ent
and t e m p o r a r y p re v e n tio n of a b s c is s io n .
In 1946, Luckw ill (55) is o la te d a s u b stan ce fro m the apple e n d o ­
s p e r m w hich he found to be a c tiv e in se ttin g p a r th e n o c a rp ic to m ato fru it.
L uck w ill and W oodcock (64) could only p a r t i a l l y identify th is s u b stan ce, but
m a in ta in e d th at the apple h o rm o n e w as not in d o le a c e tic acid.

T e u b n e r (94)

a p p a r e n tly is o la te d the s a m e s u b sta n c e from apple s e e d s and id en tified the
com pound a s ethyl in d o le a c e ta te .
Luckw ill (56) u s e d the c a p a c ity of the e x tr a c te d s u b sta n c e to set
p a r t h e n o c a r p i c tom ato f r u i t fo r a q u an titativ e m e a s u r e m e n t of the n a tu r a l
h o rm o n e p r e s e n t in the apple s e e d s.

He w as able to c o r r e l a t e the p e r io d s

of high h o rm o n e con ten t of apple s e e d s with c o r re s p o n d in g p e r io d s of re d u c e d
f r u i t drop u sin g the app le v a r i e t y Beauty of Bath (57).

In f u r t h e r s tu d ie s he

found the p e a k s of h o rm o n e a c c u m u la tio n to c o r r e l a t e w ith the c e s s a t i o n of

the f i r s t drop and the ’’June" drop (59).

T he h o rm o n e co n ten t of the s e e d s

w as found to be lo w est ju st p r i o r to the f i r s t drop, the "June" drop, and p r e h a r v e s t drop.

T h e s e p e a k s of h o rm o n e a c c u m u la tio n w e r e v e r y s i m i l a r for

the apple v a r i e t ie s , L a n e 's P rin c e A lb e rt (59) and C raw ley Beauty (61).
L uckw ill (57, 58) found a c lo s e c o r r e l a t i o n betw een the tim e of c e l ­
l u l a r f o rm a tio n of the e n d o s p e rm and the a p p e a r a n c e of high h o rm o n e content
in the ap p le s e e d s of Beauty of Bath.

He s u g g e ste d that ihe e n d o s p e rm its e lf

m ig h t be the lo catio n of the h o rm o n e p ro d u ctio n .

By s e p a r a tin g the e m b ry o

fro m the e n d o s p e rm and n u c e llu s he found that the c o n c e n tra tio n in the o u te r
la y e r s , th e e n d o s p e rm and nucellu s, w as eig h teen tim e s a s g r e a t a s in the
em bryo.

Since the n u c e llu s w as a lm o s t c o m p le te ly a b s o rb e d by the e n d o s p e rm

soon a f t e r the tim e the h o rm o n e c o n c e n tra tio n w as m e a s u r e d , it s e e m e d
p r o b a b le to him th a t the g r e a t e r c o n c e n tra tio n w as in the e n d o s p e rm .
Luckw ill (57) r e p o r t e d th a t im m e d ia te ly a f te r the c e l l u l a r fo rm a tio n
of the e n d o s p e rm of the apple, the e m b ry o e n te r e d a p e r io d of r a p id grow th
d u rin g w hich the h o rm o n e content of the s e e d d e c r e a s e d to a low le v e l.

He

s u g g e ste d a s a p o s s i b l e explanation, that the h o rm o n e p la y e d a p a r t in e m b ry o
d e v elo p m en t d u rin g the p e r io d of its ra p id growth, and thus the h o rm o n e w as
d ep leted m o r e quickly than w as p ro d u c e d by the e n d o s p e rm .

25.

MATERIALS AND METHODS

I. F ie ld S tudies on C h e m ic a l T hinn ing of P e a c h e s u sin g N aphth a le n e a c e tic Acid, N - l-n a p h th y lp h th a la m ic Acid, and 3 -c h lo ro
IPC.
A s e r i e s of s tu d ie s w e r e conducted d u rin g the p e r i o d 1955 th ro u g h
1958 to d e te r m in e the value of n a p h th a le n e a c e tic acid
th y lp h th a la m ic a c id

2

1

(NAA), N - l - n a p h -

(NPA), and 3 - c h lo r o - is o p y l- N - o h e n y l c a r b a m a t e

c h lo ro IPC) fo r b lo ss o m and f r u it thinning of p e a c h e s .

3

(3-

The s tu d ie s w e r e

p e r f o r m e d a t the Bailey fa rm in the a r e a of P on tiac in 1955 and 1956, a t the
M ich ig an State U n iv e r s ity H o r tic u ltu r a l f a rm , E a s t L a n s in g in 1956, 1957
and 1958, and at the M ichigan State U n iv e rs ity G rah am E x p e rim e n t Station,
G ra n d R ap ids in 1957.
E a c h t r e a tm e n t included five r e p lic a te d m a t u r e b e a r in g t r e e s of
m e d iu m v ig o r, ex cep t fo r c e r t a i n stu d ie s in E a s t L a n sin g in 1958, when fivey e a r - o l d e a r l y b e a r in g t r e e s w e r e used .

T h r e e to four b r a n c h e s w e r e s e l e c ­

te d in d iffe re n t a r e a s of e a c h t r e e , and a p p ro x im a te ly 500 b lo s s o m s o r f r u it
p e r t r e e w e r e u s e d fo r thinning o b s e r v a tio n s .

F in al fru it se t cou nts w e r e

m a d e e a c h y e a r the m id d le of July.
T he th in nin g t r e a t m e n t s m ad e a r e r e c o r d e d in T a b le 1.

^ A p p -L -S et, a p r o d u c t of Dow C h em ical Company, M idland, M ichigan
w as u s e d fo r NAA.
2
P e a c h -T h in , a p r o d u c t of A m e r ic a n C h em ical P aint Company, A m b le r,
P en n sy lv an ia, w as u s e d for NPA.
^ C h lo ro IPC M is c ib le , a p r o d u c t of N ia g a r a C h em ical D ivision, M id d lep o rt,
N. Y. , w as u s e d f o r 3 - c h lo ro IPC t r e a t m e n ts .

T a b le 1
T h in n in g T r e a t m e n t s on R ed hav en and H aleh av en P each T r e e s U sed in 1955, 1956,
1957 and 1958
T im e of a p p liM a te r ia l

S easo n

L o c a tio n

c a tio n (daVs
a f t e r full bloom)

Cone.
(ppm)

C o m m e n ts

NPA
NPA

1955
1955

Pontiac
P o ntiac

3
3

200
400

NPA
NPA

1956
1956

E a s t L a n s in g
E a s t L a n sin g

3
3

300
300

NPA
NPA

1957
1957

G ra n d R ap id s
G r a n d R apid s

3
3

200
250

NPA

1957

E a s t L a n s in g

3

300

NPA
NPA

1958
1958

E a s t L a n s in g
E a s t L a n sin g

3
3

250
300

H aleh aven only
H aleh av en only

NPA

1958

E a s t L a n s in g

3

250

NPA

1958

E a s t L a n s in g

3

300

F i v e - y e a r - o l d Redhaven
tre e s
F iv e -y e a r-o ld tre e s

1956

E a s t L a n s in g

28

400

1957

G ra n d R apid s

28

400

NAA

1957

E a s t L a n s in g

42

30

NAA
NAA
NAA

1958
1958
1958

E a s t L a n s in g
E a s t L a n s in g
E a s t L a n s in g

35
42
49

30
30
30

R edhaven only

NAA

1958

E a s t L a n s in g

42

30

F i v e - y e a r - o l d H alehaven
tre es

3 - c h lo ro
IPC
3 -c h lo ro
IPC

Tw ilight a p p licatio n

R edhaven only

27.

All f r u i t th in nin g t r e a t m e n t s w e r e ap p lied with a hand gun u s in g
500 pounds p r e s s u r e .

The t r e e s w e r e s p ra y e d to the d rip point.

All a p p li­

c a tio n s w e r e m ad e u n d e r f a s t d ry in g conditions, ex cep t fo r one tw ilight
a p p lic a tio n of NPA in 1956.

T h is t r e a t m e n t w as m ade a t a p p ro x im a te ly 8:30

p . m . to a s s i m i l a t e slow d ry in g con ditio ns.
F i r m n e s s of the f ru it w as e v a lu a te d in 1956 and 1957 a t the b e g in ­
ning and d u rin g h a r v e s t .

The r e a d in g s w e r e m ade at fo u r lo catio n s on the

fru it, on the d o r s a l and v e n tr a l s u tu r e s , and in the m idd le of the two ch eek s.
The p r e s s u r e s w e r e tak en w ith a M a g n e s s - T a y l o r p r e s s u r e t e s t e r equipped
w ith a 7 / 1 6 - i n c h p lu n g e r, a s su g g e ste d by Rood (83).

The siz e of the h a r ­

v e s te d f r u i t w as r e c o r d e d only in 1956 u s in g s ta n d a rd f ru it s iz in g r in g s .
Studies w e r e conducted in 1958 u sin g p lo ts e s ta b lis h e d d u rin g 1957.
T h e p lan t r e g u l a t o r thinning t r e a t m e n ts ap p lied in 1957 at the M ichigan State
U n iv e r s ity H o r tic u ltu r a l fa rm , E a s t L a n sin g w e re u se d to e v alu ate the i n ­
flu e n ce of NPA and NAA on the n u m b e r of Redhaven and H alehaven flow er
buds the follow ing y e a r .

F lo w e r buds w e r e counted in A p ril 1958 on six u n ­

b ra n c h e d t e r m i n a l s , two t e r m i n a l s 2 to 5 1/2 inches in length, two t e r m i n a l s
5 1 /2 to 9 1 /2 in ch es in length, and two t e r m i n a l s 9 1 /2 to 15 in ch es in length,
s e le c te d on e a c h t r e e .
of Illin o is in 1955 (43).

T h is c o n fo rm e d w ith the technique u s e d by Kelley

II.

F ie ld S tudies C o m p a rin g N a tu ra l Blossom and F r u i t Drop
w ith th a t R e s u ltin g fro m the Use of N a p h th a le n e a c e tic Acid
and N - 1-n a p h th y lp h th a la m ic Acid.

In o r d e r to o b s e r v e the p a t t e r n of f r u it drop, a study w as in itia te d
in 1958 a t the M ichigan State U n iv e rsity H o r tic u ltu r a l f a rm , E a s t L a n sin g
to c o m p a r e the n a tu r a l drop of b lo s s o m s and young p e a c h f r u its with the
drop r e s u l t i n g fro m the u se of NAA and NPA fo r b lo sso m and f r u it thinning.
T w enty u niform m a t u r e b e a r in g R edh aven t r e e s w e r e s e le c te d fo r th is in ­
v e s tig a tio n to p ro v id e five t r e e s p e r tre a tm e n t, of w hich five t r e e s w e re
t r e a t e d and five w e r e u s e d a s a c o n tro l.

A m in im u m of t h r e e b r a n c h e s

w e r e s e le c te d in d iffe re n t a r e a s of e a c h t r e e and a p p ro x im a te ly 500 b lo s s o m s
p e r t r e e w e r e o b s e r v e d a t sp e c ific p e r io d s to e v a lu a te f r u it developm ent
and dro p.
An a p p lic a tio n of 30 ppm of n a p h th a le n e a c e tic a c id (NAA) w as m ad e
on five of the ten s e le c te d t r e e s two w eek s a f t e r " sh u ck -o ff", June 14, when
con d itio n s w e r e fa v o ra b le f o r f a s t d rying.

The b lo s s o m s and developing

f r u i t s on the s e le c te d b r a n c h e s of a ll ten t r e e s w e re counted at w eekly i n t e r ­
v a ls fro m bloom (May 3) to two w eek s a f t e r " sh u ck -o ff" (June 14).

A fte r

th is tim e d ro p p ed f r u i t s of the NAA t r e a t m e n t and the c o n tro l t r e a t m e n t
fro m the s e le c te d b r a n c h e s of a ll ten t r e e s w e r e counted tw ice w eekly until
i m m a t u r e fru it drop w as c o m p le te d by July 4.

An add ition al count w as m ad e

the m id d le of July to ch eck fo r p o s s ib le ad d itio n al fru it drop o c c u r r i n g a f te r
July 4.

It should be noted th at the ten R edhaven t r e e s r e c e iv e d uniform

29.

in s e c tic id e and fungicide a p p lic a tio n s d u rin g th is p e r io d of o b s e rv a tio n .
E a c h tim e drop w as counted the n u m b e r of b lo s s o m s and f r u it r e ­
m a in in g on e a c h b r a n c h w as r e c o r d e d .

The drop p e r 100 b lo s s o m s o r f r u i t s

fo r e a c h b r a n c h a t e a c h tim e in te rv a l w as found by dividing the n u m b e r of
b lo s s o m s o r f r u its hanging a t the tim e of p r e v io u s counting date into the n u m ­
b e r th a t had dro p p ed d u rin g th is in te rv a l (94).

The daily drop p e r 100 b l o s ­

s o m s o r f r u its w as then co m pu ted fo r each in te rv a l by dividing by the n u m b e r
of days b etw een the r e c o r d d a te s .
In a s i m i l a r study counts w e r e m ade on tag ged b r a n c h e s of NPA
t r e a t e d and c o n tro l R edhaven t r e e s a t bloom and at 14 days a f t e r bloom in
o r d e r to d e te r m in e the a p p r o x im a te tim e the b lo s s o m s o r f r u it dropped.
F in a l co unts w e r e m ad e July 12 on th e s e s a m e t r e e s .
The p e a c h b lo s s o m s which fell d u rin g the 1 4 -day p e r io d a f t e r bloom
w e r e e x a m in e d m a c r o - and m ic r o s c o p ic a lly .

F o r the m ic r o s c o p e study the

o v u le s of the p e a c h b lo s s o m s w hich d ro p p ed w e r e k illed and fixed in 50 p e r ­
cen t FAA (38) fo r 24 h o u rs.

The o v u les w e r e r in s e d th r e e tim e s in 50 p e r c e n t

ethyl alco h o l fo r 30 m in u te s each, fro z e n in a 10 p e r c e n t g elatin m ediu m , and
th en cut into s e c tio n s of 20 m i c r o n s in th ic k n e s s with a Model 880 A m e r ic a n
O p tical Com pany f r e e z in g m ic r o to m e .

T he s e c tio n s w e r e p la c e d on a g la s s

s lid e and sta in e d t h r e e m in u te s w ith D e la f ie ld 's H em atoxylin.

A fte r the s ta in

w a s re m o v e d fro m the slide, the s e c tio n s w e re m ounted in g ly c e r in on m ic r o s c o p e
s lid e s and c o v e r s lip s w e r e p la c e d on them .
a Z e i s s N r. 250190 m ic r o s c o p e .

T he s e c tio n s w e re then s tu d ie d u n d er

30.

III. A n ato m ical In v estig atio n s of the D eveloping E m b ry o and E n d o ­
s p e r m of H aleh av en and R edhaven P each.
F lo w e r s and f ru it w e r e g a th e r e d fro m a single m a t u r e b e a r in g H a le ­
haven p e a c h t r e e in 1957 and fro m a sing le m a tu r e b e a r in g Redhaven and
H alehaven p e a c h t r e e in 1958 to study the developing e m b ry o and e n d o s p e rm
of young p e a c h f r u it s .
H o r tic u ltu r a l f a rm ,
NAA.

The t r e e s lo cated on the M ichigan State U n iv e rsity

E a s t L ansing, w e r e r e p r e s e n t a t i v e of th o se t r e a te d w ith

T h e y r e c e i v e d the s a m e in se c tic id e and fungicide a p p lic a tio n s as tho se

of the NAA t r e a t m e n ts .
At e a c h tim e of sam pling, f r u its w e r e taken from one b ra n c h in o r d e r
to lo c a liz e the th inn in g effect to only th at b ra n c h on the t r e e .

Blossom a n d / o r

f r u it c o lle c tio n s w e r e m ad e tw ice w eekly on the H aleh av en t r e e d u rin g 1957
fro m fo u r days a f te r bloom (May 6) to eight w eek s a f t e r bloom (June 28).

In

1958, b lo ss o m and fru it c o lle c tio n s w e r e m ad e on the Redhaven t r e e at full
bloom (May 3); the fo u rth day a f t e r full bloom; one w eek a f t e r full bloom; and
at w eekly i n te r v a ls t h e r e a f t e r until five w eeks a f t e r full bloom (June 7), a f t e r
w hich tim e the fre q u e n c y of c o lle c tio n s w as in c r e a s e d to tw ice w eekly th ro u g h
the eigh th w eek a f t e r bloom (June 28).

H alehaven f r u its w e r e c o lle c te d tw ice

w eekly b eginning five w eek s a f t e r bloom (June 7) and ending the eighth w eek
a f t e r bloom .

A final f r u it c o lle c tio n of Redhaven and H alehaven w as m ad e

nine w eeks a f t e r bloom, 1958, fo r m a c r o - m e a s u r e m e n t s .
A p p ro x im a te ly 25 p e r s i s t i n g b lo s s o m s a n d / o r fru it w e re c o lle c te d

a t e a c h s a m p lin g fro m e a c h v a r ie ty .

The o v a r i e s w e r e d is s e c te d th ro u g h

the v e n tr a l and d o r s a l s u tu r e s w ith a r a z o r blade ’keeping the seed s^ in tact.
F iv e of the 25 f r u its in 1957 and ten of the 25 f r u its in 1958 c o lle c te d d u rin g
the p e r io d of two w eek s a f t e r full bloom to eight w eeks a f t e r bloom w hich
a p p e a r e d to have only one viab le s e e d w e r e u s e d for g row th m e a s u r e m e n t s .
All R edhaven b lo s s o m s and f r u i t s c o lle c te d from the tim e of full bloom to
two w eeks a f t e r bloom co n tain ed two viable ovules^.
M e a s u r e m e n ts ta k e n w e r e a s follows:
P e r i c a r p length:

d ista n c e betw een the p ed icel a tta c h m e n t and the

line of d e m a r k a tio n w h e re the sty le a r i s e s fro m the o v a ry .
P e r i c a r p t r a n s v e r s e d ia m e te r : g r e a t e s t c r o s s - s e c t i o n a l d ia m e te r of
the fru it.
Seed length: lo n g est longitudinal d ista n c e of the seed.
Seed width: g r e a t e s t c r o s s - s e c t i o n a l d ia m e te r of the seed.
M e a s u r e m e n t s w e r e m a d e with a m e t r i c r u l e r to the n e a r e s t 0. 5 m i l l i m e t e r .
L en gth of the p e r i c a r p and s e e d w as u s e d in o r d e r to m e a s u r e the i n c r e m e n t s
of grow th (98).

W idth w as tak en only to su b sta n tia te the gro w th in c r e m e n ts .

T he s e e d s u s e d for m e a s u r e m e n ts w e re killed and fixed in 70 p e r c e n t
FAA

2

and then d eh y d rated , u sin g the t e r t i a r y butyl alcohol m ethod d e s c r ib e d

by Jo h an sen (38).

The m a t e r i a l w as then em b ed ded in F i s h e r ti s s u e m a t with

■^In th is study the t e r m "ovule" w as u s e d befo re syngam y and the t e r m " se e d "
a f te r w a r d .
2
A so lu tio n of 5 m i l l i l i t e r s of 37 to 40 p e r c e n t fo rm ald eh y d e, 5 m i l l i l i t e r s of
g la c ia l a c e tic a c id and 90 m i l l i l i t e r s of 70 p e r c e n t ethyl alcohol.

32.

a m e ltin g point of 53-55° C.

The p a r a ff in em bedd ed m a t e r ia l w as cut lo n g i­

tu d in a lly into s e c tio n s 10 to 12 m ic r o n s in th ic k n e ss w ith a Model 820 A m e r ic a n
O ptical C om pany r o t a r y m ic ro to m e .

The s e c tio n s w e re then m ounted in s e r i e s

on s ta n d a r d m ic r o s c o p e s lid e s , u sin g H aupt’s ad h esiv e (38).

The p a r a ff in w as

r e m o v e d fro m the s e c tio n s w ith xylol and the s e c tio n s w e r e s ta in e d five s e c ­
onds w ith f a s t g r e e n (38).

The s e c tio n s w e r e m ounted in C la r ite and allow ed

to d ry fo r four days b e fo re m ic r o s c o p ic exam in atio n .
All m ic r o s c o p ic e x a m in a tio n s w e r e m ade with a Z e i s s N r. 250190
m icro sco p e.
m e n ts .

A c a l i b r a t e d o p tical len s w as u s e d fo r all m ic r o s c o p ic m e a s u r e ­

L eng th and w idth of the em b ry o , the en d o sp erm , and the e m b ry o s ac

of five s e e d s w e r e o b s e rv e d fo r e a c h tim e of sam pling.

The ten f r e s h s e e d s

fro m both H aleh av en and R edhaven f r u its of the final collection, July 5, 1958,
w e r e u s e d only fo r m a c r o - m e a s u r e m e n t s .
In ad* d ition to the m ic r o s c o p ic e x am in atio n s of the m a t e r i a l em b ed d ed
in p a r a ff in in 1958 ten f r u it s w e r e s e le c te d daily from e a c h R edhaven and
H alehaven t r e e fro m June 11 (five and o n e -h a lf w eeks a f t e r bloom) to June 20,
1958, to study the dev elo p m en t of the e n d o s p e rm .

The s e e d s of th e s e f r u its

w e r e re m o v e d , killed and fixed in 50 p e r c e n t FAA (38).

A fte r 24 h o u rs the

o v u les w e r e r i n s e d thoro ug hly with th re e changes of 50 p e r c e n t ethyl alcohol.
E a c h s e e d w as then cut with a s h a rp r a z o r blade longitudinally th ro u g h the
m ic r o p y le to ex p ose the e m b ry o sac.

The em b ry o sac w as re m o v e d fro m

33.

the s e e d by p u llin g the n u c e llu s t is s u e away from the e m b ry o sac with d i s ­
s e c tin g n e e d le s u n d er a d is s e c tin g m i c ro s c o p e .

The e m b ry o s ac w as p la c e d

on a g l a s s m i c r o s c o p e s lid e and s ta in e d t h r e e m in u te s in D e la fie ld 's h e m a ­
toxy lin .

A fte r the e x c e s s s ta in w as rem o v ed , the m a t e r i a l w as m ounted

in g ly c e r o l and then ex am in ed u n d er a m ic ro s c o p e .

T h e s e e x a m in a tio n s

w e r e m a d e p r i m a r i l y to d e te r m in e when the e n d o sp e rm changed from a
f r e e - n u c l e a r condition to a c e l l u la r s ta te .
P h o to m ic ro g r a p h s w e r e tak en with an E xakta VX c a m e r a u sin g a
m i c r o s c o p e a d a p te r .

The light w as ob tained fro m a type 3 1 -3 3 -2 6 Bausch

and L om b O ptical Com pany m ic r o s c o p e light with a ground g la s s f ilt e r
(39375) and a blue g la s s f i l t e r (39370) p la c e d betw een the light s o u rc e and
s u b - s t a g e m i r r o r of the m ic ro s c o p e .
the b lack and w hite p h o to - m ic r o g r a p h s .

Kodak P lu s-X film w as u se d fo r takin g

IV. N a tu ra l H orm o ne Content and C o n c e n tra tio n of Young R edhaven
P each Seeds a s R e la te d to E a r l y G row th and Development.
Luckw ill (57) found that n a tu r a l h o rm o n e content of apple s e e d s
w as r e l a t e d to n a tu r a l f r u it drop.

On the b a s is of this finding, a stud y w as

i n itia te d to d e te r m in e the r e la t iv e c o n c e n tra tio n and content of the n a tu ra l
h o rm o n e in developing p e a c h s e e d s.
F r u i t c o lle c tio n s w e r e m ad e June 2 , 1958, fo u r w eek s a f t e r full
bloom , and a t w eekly i n te r v a ls t h e r e a f t e r for a p e r io d of four w eeks fro m
five R edhaven t r e e s at the M ichigan State U n iv e rsity H o r tic u ltu r a l fa rm ,
E a s t L a n sin g .

F iv e h u n d re d f r u its w e r e c o lle c te d on each of the f i r s t two

s a m p lin g d ates, but only 300 f r u i t s w e re g a th e r e d e a c h tim e t h e r e a f t e r .
E qual n u m b e r s of f r u i t s w e r e ta k e n from each of the five t r e e s by s tr ip p in g
in dividual b r a n c h e s .

F r u i t w ith a b o r te d s eed s w e re d is c a rd e d .

w e r e s p lit w ith a r a z o r blade and the s eed s rem o v ed .

The f r u its

The s e e d s w e r e then

w eighed, w ith a s e p a r a t e count and w eight m ade fo r the fru it co ntaining
one o r two s e e d s.

F ollow ing th is o p e ra tio n the f r e s h sin gle and double s e e d s

w e r e p la c e d to g e th e r in a p l a s ti c bag and t r a n s f e r r e d im m e d ia te ly to s to r a g e
a t -10°C .
When tim e p e r m itte d , the fro z e n plan t m a t e r i a l w as next e x t r a c t e d
w ith cold, p e r o x i d e - f r e e diethyl e t h e r a s d e s c r ib e d by Van O v erb eek et aL (104)
To c a r r y out th is p r o c e d u r e , the s e e d s w e r e ground in a m o r t a r and p e s tle
w ith san d add ed to aid in the grinding.

About 50 m i l l i l i t e r s of diethyl e th e r

35.

w e r e ad d ed to the m ix tu re d u rin g the g rin d in g p r o c e s s .

The co n ten ts w e r e

e m p tie d into a 5 0 0 - m i l l i li t e r E r le n m e y e r f la s k and p la c e d in s to r a g e at 2° C
f o r eigh t h o u rs .

The s u p e rn a ta n t w as decan ted fro m the flask.

T he ground

s e e d s w e r e w a sh e d t h r e e tim e s with 50 m i l l i l i t e r s of diethyl e th e r and ad d ed
to die o r ig in a l s u p e rn a ta n t so a s to e x tr a c t the r e m a in in g n a tu ra l h o rm o n e .
T h is e x t r a c t w as then s e p a r a t e d into a c id and n e u tra l fra c tio n s w ith 200
m i l l i l i t e r s of five p e r c e n t sodium b ic a rb o n a te solution by m e a n s of a s e p a r a ­
t o r y funnel (96).

T he n e u tr a l s u b s ta n c e s re m a in e d in the e th e r la y e r, while

the a c id s u b s ta n c e s p a s s e d into the sodium b ic a rb o n a te la y e r .

The b ic a rb o n a te

so lu tion w as ac id ifie d to pH 2. 8 with h y d ro c h lo ric acid and e x tr a c te d w ith 200
m i l l i l i t e r s of diethyl e th e r .

Both fra c tio n s , acidic and n e u tra l, w e r e c o n c e n ­

t r a t e d to five m i l l i l i t e r s u n d er r e d u c e d p r e s s u r e .
T h r e e dilution q u an tities, 0. 01, 0. 05 and 0. 10 m i l l i l i t e r s of each acid
and n e u tr a l fra c tio n of the diethyl e th e r e x t r a c t w e re p la c e d w ith a m i l l i l i t e r
s y rin g e into individual p o r c e l a i n bo ats to which had been added s m a ll s t r i p s
of f i l t e r p a p e r .

A fte r the e t h e r e x t r a c t s had ev ap o rated , one m i l l i l i t e r of

a p h o s p h a te - c i t r i c a c id buffer s o lu tio n 1 a s u se d by N itsc h and N itsch (78) w as
p la c e d in e a c h boat.

S ta n d a rd s of 0. 01, 0. 10 and 1. 00 m i c r o g r a m s of indole-

a c e tic a c id (IAA) and ethyl in d o le a c e ta te (EtIA) w e r e p la c e d a ls o in the bo ats
p r e c e d in g the ad d itio n of the b uffer solution.

The c o n tro l t r e a t m e n t c o n s is te d

of the bu ffer solu tion alone.
1Double c o n c e n tra tio n of p h o s p h a te - c i tr i c a c id buffer solution is m ad e up of
0. 359 g r a m s of K^HPO^, 0. 204 g r a m s of c it r i c acid, 4. 0 g r a m s of s u c r o s e in
100 m i l l i l i t e r s of w a te r solution.

36.

The avena s tr a ig h t grow th t e s t w as u sed a s p a r t of the b io a s s y study
a s d e s c r ib e d by N itsc h and N itsch (78) and m o d ified by T e u b n e r (96).

T h is

m eth o d of biolo gical a s s y w as c h o se n in ste a d of the to m ato o v a ry t e s t a s u s e d
by L u ck w ill (55) b e c a u s e of the s im p lic ity of its p r o c e d u re .
f o r o b tain in g oat c o le o p tile s w as a s follows:

The p r o c e d u r e

Husked s e e d s of the Brighton

v a r i e t y of o a ts w e r e p la c e d in d is tille d w a te r and e v a c u a te d in a suction fla sk .
T h e s e e d s w e r e r e m o v e d fro m the suction fla sk and soak ed fo r two h o u rs.
The so a k w a t e r w as d is c a r d e d and the se e d s w e re r in s e d twice with d is tille d
w a te r .

T he s e e d s w e r e then p la c e d groove side down on a wet p a p e r towel

c o v e r in g a d e s s i c a t o r p la te w ith the v isib le r a d ic a ls sligh tly o v e r the edge
of the d e s s i c a t o r p la te .

The p la te with the s e e d s w as p la c e d in a c u ltu re

d is h w ith su fficien t d is tille d w a te r to keep the p a p e r towel wet.

T he c u ltu re

d is h w ith its co n ten ts w as p la c e d in a d a r k in cu b ato r fo r th r e e days.

T he

g e r m in a tin g s e e d s w e r e e x p o sed to two h o u rs of r e d light 24 h o u rs a f te r
they w e r e p la c e d in the d a r k in c u b a to r in o r d e r to inhibit elongation of the
f i r s t in te rn o d e .

A fte r t h r e e days in the in cub ator, the g e r m in a tin g s e e d s w e r e

r e m o v e d and the c o le o p tile s w e r e cut in uniform s e c tio n s of five m i l l i m e t e r s ,
d is c a r d in g the a p ic a l t h r e e to fou r m i l l i m e t e r s .

The co leo p tile s e c tio n s w e r e

then th r e a d e d on thin g la s s ro d s five c e n tim e te r s long, th r e e o r fo u r to a rod.
The le a f in sid e the co leo p tile c y lin d e r w as punched out d u rin g the th re a d in g
o p e ra tio n .

All c u ttin g and th re a d in g o p e ra tio n s w e r e done u n d e r r e d light.

T h r e e r o d s w ith a total of 10 s e c tio n s w e r e p la c e d in e a c h boat.

In tu rn , the

37.

b o ats w e r e put into p e t r i d is h e s and kept in a d a rk in c u b a to r for 24 h o u rs.
M e a s u r e m e n t s of the co leo p tile s e c tio n s following the in c u b a to r t r e a t m e n t w e r e
m a d e w ith a r u l e r to the n e a r e s t 0. 5 m i l l im e t e r .
S ta n d a rd c u r v e s showing the r a t e of grow th of the co leo p tile s e c tio n s
a s in flu en c ed by the d iffe re n t c o n c e n tra tio n s of IAA and EtIA w e r e m ad e on s e m ilo g rith m ic g ra p h p a p e r w ith the c o n c e n tra tio n s in p a r t s p e r m illio n c h a r te d
lo g rith m ic a lly .

The quantity of the n a tu ra l h o rm o n e s w as b a s e d on m i c r o g r a m

e q u iv a le n ts of IAA fo r the a c id f ra c tio n and m ic r o g r a m eq u iv alen ts of EtIA for
the n e u tr a l f ra c tio n .

T h e h o rm o n e content of the s e e d s w as e x p r e s s e d a s m i c r o ­

g r a m e q u iv a le n ts p e r 100 f ru its ; and h o rm o n e c o n c e n tra tio n in the s e e d s w as
e x p r e s s e d a s m ic r o g r a m eq u iv alen ts p e r g ra m of f r e s h weight of the seed s.
P a p e r c h ro m a to g ra p h y w as u tilized fo r a q u alitativ e a n a ly s is of the a c id
and the n e u tr a l f r a c tio n s of the p each se e d e x tr a c t (92).

U sing a o n e - m i l l i l i t e r

sy rin g e , 0. 05 m i l l i l i t e r s of the acid and 0. 05 m i l l i li t e r s of the n e u tr a l e x tr a c t
w e r e sp o tted on d iffe re n t s t r i p s of t h r e e - q u a r t e r inch W hatm an No. 1 f i l t e r p a p e r .
Both f r a c tio n s of the e x t r a c t w e r e p a r titio n e d by a so lvent m ix tu re co m p o se d
of 2 -p ro p a n o l, a m m o n ia, w a t e r a s a r a tio of 8:1:1 volum e to volum e (92).
T he d rie d c h r o m a t o g r a m s w ith the p a r titio n e d e x t r a c t s w e r e scan n ed
fo r u l tr a v io le t f lu o r e s c e n t spo ts with a 2537 A ng strom " M in e r a lig h t” .

The d rie d

c h r o m a to g ra p h e d p a p e r w as then cut into s m a ll s e c tio n s and b io a ss a y e d by the
av en a s tr a i g h t - g r o w t h m eth o d p r e v io u s ly m entioned.

E h r l i c h e r 's s p r a y r e a g e n t

w as a p p lie d to s i m i l a r t r e a t e d c h r o m a to g r a m s fo r f u r th e r q u a lita tiv e a n a ly s is a s
d e s c r i b e d by Sen and L eopold (86).

38.

RESULTS

I. F ie ld Studies on C h e m ic a l Thinning of P each es U sing N - l - n a p h th y lp h th alam ic, N a p h th alen eacetic Acid, and 3 - c h lo ro IPC.
T he findings fro m the u se of N - 1-n a p h th y lp h th alam ic a c id (NPA),
n a p h th a le n e a c e tic a c id (NAA), and 3 - c h lo ro IPC a s thinning a g e n ts f o r R e d ­
h av en and H aleh av en p e a c h e s u n d e r field conditions a r e given in T a b le s 2
and 3.
In 1955 fru it set on R edhaven and H alehaven t r e e s in the Pontiac a r e a ,
s p r a y e d w ith NPA a t 200 and 400 ppm, w as not sign ifican tly d ifferen t fro m the
c o n tro l t r e a t m e n t s (Table 2).

How ever, NPA app lied at 300 ppm in 1956 in

E a s t L a n s in g on the s a m e v a r i e t i e s r e s u l t e d in sig n ificant thinning.

T h e re

w a s no sig n ifican t d iffe re n c e betw een day and tw ilight ap p lic a tio n s of NPA
m ad e in 1956, even though it had b een su g g ested that slow d ry in g con dition s
would m a k e NPA m o r e effective.

B ecause of the o v e r thinning at 300 ppm in

1956, NPA w as u s e d a t 200, 250 and 300 ppm in 1957.

No sign ifican t thinning

o c c u r r e d a t the lo w er c o n c e n tr a tio n s in 1957 (Table 2) and ev en though t h e r e
w as sig n ifican t th inn ing a t 300 ppm, the fru it on both the R edhaven and H a le ­
h av en t r e a t e d t r e e s had to be hand thinned.
In 1958, sig n ifican t re d u c tio n of fru it set o c c u r r e d when 300 ppm of
NPA w as ap p lied to f iv e - y e a r - o ld Redhaven and H alehaven t r e e s and when 250
ppm of NPA w as ap p lied to f iv e - y e a r - o l d R edhaven t r e e s (T able 2).

H ow ever,

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the Use of N- 1-Naphthylphthalamic Acid (NPA) as a Chemical Thinning Agent on R ed­
haven and Halehaven Peach T rees

39.

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the Use of 3-Chloro IPC and Naphthaleneacetic Acid (NAA) as Thinning Agents on
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no s ig n ific a n t th in n in g w as r e a l i z e d in 1958 on 1 0 - y e a r - o ld H alehaven t r e e s
t r e a t e d w ith NPA a t 250 ppm and 300 ppm .

In 1958 the heavy fru it drop of

the f iv e - y e a r - o l d R edhaven and H alehaven t r e e s o c c u r r e d d u rin g the p e r io d
M ay 10 to 17, se v e n to fo u rte e n days a f te r bloom .

T h is w as in a c c o r d w ith

E d g e rto n and Hoffm an (29) who r e p o r t e d that the heavy drop fro m NPA t r e a t e d
p e a c h t r e e s o c c u r r e d about 10 days a f t e r bloom.
The re d u c tio n in f r u it s e t on Redhaven and H alehaven t r e e s t r e a t e d
w ith 3 - c h lo ro IPC a t 400 ppm in 1956 w as significant, but when u s e d a t 400 ppm
in 1957, sig n ific a n t thinning o c c u r r e d only on H alehaven t r e e s a t the G ra h a m
E x p e rim e n t Station, G ra n d R apids (T able 3).

However, in both 1956 and 1957,

all R edh av en and H aleh av en t r e e s r e c e iv in g 3 -c h lo ro IPC thinning t r e a t m e n ts
p ro d u c e d u n d e s ir a b le "b eak ed shaped" p e a c h e s (F ig u re 1).

Not only w e r e the

p e a c h e s m iss h a p e n e d , but the "beaked" p o rtio n b ecam e soft when the p e a c h e s
r e a c h e d the f i r m - r i p e stag e m ak in g them e a s y to b ru is e , a condition v e r y
fa v o ra b le fo r the d evelop m ent of brow n ro t.

Because of the u n d e s ir a b le effect

fro m 3 - c h lo r o IPC on p e a c h e s , the u se of the plant r e g u la to r fo r thinning p e a c h
t r e e s w as te r m i n a t e d in 1957.
T he u se of NAA 42 days a f t e r bloom at 30 ppm on R edhaven and H a le ­
h aven t r e e s in 1957 and 1958 gave sig n ifican t fru it thinning (Table 3 and F i g u r e s
2 and 3) ex cep t fo r the f i v e - y e a r - o l d H alehaven t r e e s .

Also, the u s e of NAA

in 1958 on f i v e - y e a r - o l d and o ld e r R edhaven t r e e s , at the s a m e co n c e n tra tio n ,

F ig u re 1
Injury on Redhaven p e a c h e s fro m 3 - c h lo ro IPC.
Top row: uneven developm ent of the fru it
M iddle row: u n d e s ira b le e n la r g e m e n t of b a s e of the style,
’’beaked f r u i t ”
Bottom row: d e s ir e d shape for m a tu r e Redhaven p e a c h e s .

42.

:

43.

35 d ays a f t e r bloom r e s u lt e d in sig n ifican t thinning.

H ow ever, when NAA

w as a p p lie d 49 days a f t e r bloom, on Redhaven, no sig n ifican t thinning w as
a c c o m p lis h e d (T able 3).

Even when thinning w as sig n ifican t fro m the u se

of NAA in 1958, light hand thinning w as n e c e s s a r y .

Injury to the te r m i n a l

g row th of the R edhaven t r e e s fro m the ap p licatio n of NAA w as a p p a re n t,
but a p p e a r e d to have little c o m m e r c ia l sig nifican ce.

F o liag e in ju ry on H ale-

hav en t r e e s w as not a s s e v e r e as on Redhaven.
F ru it F irm n ess:

As f ir m n e s s of flesh of p e a c h e s has been found

to be a fa v o ra b le index fo r m a tu r ity (83), data of f ir m n e s s of the f ru it fro m
p e a c h t r e e s t r e a t e d w ith NPA, NAA and 3 -c h lo ro IPC a s thinning ag en ts w e re
r e c o r d e d a t h a r v e s t tim e in 1956 and 1957.

T h e se data a r e s u m m a r iz e d in

T a b le 4.
R edhaven f r u its fro m t r e e s of the NPA t r e a t m e n ts m ad e in E a s t L a n s in g
in 1956 r e a c h e d m a tu rity , a s m e a s u r e d by f ir m n e s s of flesh, a p p ro x im a te ly
t h r e e days e a r l i e r than th o se fro m the co n tro l t r e e s .

It w as c o n je c tu r e d that

th is e a r l i e r m a t u r i ty w as r e l a t e d to the light fru it set on the t r e a t e d t r e e s
r a t h e r than to the NPA tr e a t m e n t.

In 1957 th e r e w e re no sig n ifican t d iff e r e n c e s

in f i r m n e s s of f ru it t r e a t e d with NPA and th o se r e c e iv in g no t r e a t m e n t (Table 4).
Since fru it s e t w as not re d u c e d by the u se of NPA at 200 o r at 250 ppm in 1957,
it s e e m e d a p p a r e n t that the e a r l y rip e n in g of the f ru it on the NPA t r e a t e d t r e e s
in 1956 w as not an influence of the c h e m ic a l, but the r e s u l t of a light set of
f r u it on the t r e e s at h a r v e s t tim e (T able 2).

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of Redhaven and Halehaven Peaches at Harvest as Affected by Various Plant Regulator
in 1956 and 1957

Thinning Sprays

44.

45.

R ed hav en f r u it on t r e e s t r e a t e d with 3 -c h lo ro IPC w e r e l e s s firm
in both 1956 and 1957 than th o se of the c o n tro l tr e a tm e n t (Table 4).
T he use of NAA a s a thinning agent in 1957 had no a p p a r e n t influence
on the r a t e of rip e n in g of Redhaven f r u it (Table 4).
As found fo r the R edhaven in 1956, H alehaven f r u its on NPA t r e a t e d
t r e e s m a t u r e d a few days e a r l i e r than the u n tre a te d f r u it when e v a lu a te d by
f i r m n e s s of fle sh .

H ere, also, e a r l y m a tu rity a p p e a r e d to be the r e s u l t of

r e d u c e d f r u it s e t on the NPA t r e a t e d t r e e s , r a t h e r than to a d ir e c t rip e n in g
in fluence of the NPA compound, a s th e r e w e r e no d iffe re n c e s in f ir m n e s s of
f le s h betw een the NPA and c o n tro l t r e a tm e n t in 1957 (Table 4).
T he u se of 3 - c h lo ro IPC on H alehaven as a thinning agent in 1956 and
1957 r e s u l t e d in e a r l i e r rip e n in g of the fru it when c o m p a re d w ith the co n tro l
t r e a t m e n t (Table 4).

P o ssib ly th at the 3 -c h lo ro IPC com pound w as r e s p o n s ib le

f o r the e a r l i e r rip e n in g of the t r e a t e d fru it of both Redhaven and H alehaven as
the r e d u c tio n of fru it s e t w as not e x c e s s iv e (Table 3).
F r u i t Size:

The s iz e ra n g e of 100 p e a c h e s p icked at h a r v e s t tim e

fro m the t r e e s of the d iffe re n t thinning t r e a t m e n ts in E a s t L a n sin g in 1956
a r e given in T a b le 5.
As exp ected, the d e g re e of thinning r e s u ltin g from the c h e m ic a l t r e a t ­
m e n ts d i r e c t ly in fluenced the s iz e of the h a r v e s te d p e a c h e s .

The fru it of R e d ­

haven and H aleh av en fro m the NPA t r e a t m e n ts w e re the la r g e s t, and th e s e

F ig u re 2
Typical b ra n c h e s of a Redhaven p e a c h t r e e s p ra y e d w ith naphthalene a c e tic a c id at 30 ppm 42 days a f t e r bloom .
fo re the o c c u r r e n c e of fru it drop.

P ic tu re tak en b e ­

Note the s iz e of the a b o rte d

f ru its .

F ig u r e 3
T y pical b ra n c h e s of a Redhaven p e a c h t r e e s p r a y e d w ith nap h th alen e a c e tic a c id a t 30 ppm 42 days a f t e r bloom .
o c c u r r e n c e of f r u it drop.

P ic tu r e a f t e r the

46.

47.

t r e e s w e r e thinned the h e a v ie s t.

The Redhaven p e a c h e s fro m the 3 -c h lo ro

IPC t r e a t m e n t s w e r e in te rm e d ia te in size , and the p e a c h e s fro m the H alehaven
t r e e s t r e a t e d w ith 3 - c h lo ro IPC and th o se from the u n tre a te d t r e e s w e re the
sm allest.
The Effect of NAA and NPA on F lo w e r Buds:

Since te r m i n a l in ju ry

to the R edhaven and H alehaven t r e e s fro m the a p p lic a tio n s of NAA in 1957
w as v e r y a p p a re n t, an ev alu atio n of the effect that NAA and NPA m ay have on
the n u m b e r of flow er buds w as m ad e in the s p rin g of 1958.

The effect of NPA

and NAA on flo w er bud f o rm a tio n when u s e d on Redhaven and H alehaven t r e e s
a r e s u m m a r i z e d in T a b le 6 a s the a v e ra g e n u m b er of flo w er buds p e r l in e a r
foot of t e r m i n a l growth.
The a v e r a g e n u m b e r of flow er buds on te r m in a l grow th of Redhaven
t r e e s t r e a t e d with NAA at 30 ppm 42 days a f t e r bloom the p re v io u s g row ing s e a so n
w as sig n ifican tly r e d u c e d to 7. 0 when c o m p a re d to the a v e ra g e n u m b e r of flow er
buds on the t r e e s of the NPA and co n tro l tr e a t m e n ts , 17. 0 and 11. 9 r e s p e c tiv e ly
(T able 5).

T h e r e w as a lso a sig n ifican t in c r e a s e in the a v e r a g e n u m b e r of R e d ­

haven flo w e r buds on t r e e s t r e a t e d with NPA at 300 ppm th r e e days a f t e r bloom in
1957 when c o m p a r e d with the co n tro l t r e e s , 17. 0 a s c o m p a re d to 11. 9 buds p e r
l i n e a r foot of t e r m i n a l grow th.

The re d u c tio n in flo w er buds in 1958 from the u se

of NAA on H alehaven t r e e s at 30 ppm 42 days a f te r bloom in 1957 w as sig nifican t,
12. 8 flo w e r buds p e r l i n e a r foot, a s c o m p a r e d to 17. 4 buds fo r the NPA tr e a tm e n t.
A lthough not sig n ifican tly differen t, the a v e r a g e of 12. 8 flo w er buds p e r lin e a r foot
in 1958 on p e a c h t r e e s s p ra y e d with NAA in 1957 w as le s s than the a v e r a g e of 16. 1
flo w e r buds p e r foot fo r the c o n tro l t r e e s .

T a b le 5
Size of R edhaven and H alehaven P e a c h e s a s Influenced by the U se of N- 1 -N aphthylp h th a la m ic A cid (NPA) and 3 -C h lo ro IPC a s T hinning S prays, 1956
V a r ie ty
M a te r i a l
C o n c e n tra tio n
(ppm)

C o ntro l

Redhaven
NPA
3- ch loro
IPC
300
400

H alehaven
C ontrol
NPA
300

3 -c h lo ro
IPC
400

Size ra n g e of 100 p e a c h e s a t h a r v e s t
1 1/8 - 2 in.

89

0

6

33

11

25

2 - 2 1 /4 in.

11

0

69

36

33

64

2 1 / 4 - 2 3 /4 in.

0

56

25

31

56

11

2 3 / 4 - 3 1/ 2 in.

0

44

0

0

0

0

T able 6
T h e E ffect of N aphthalene a c e tic Acid (NAA) and N - l-N a p h th y lp h th a la m ic A cid (NPA)
A pplied in 1957 on the F lo w e r Buds on Redhaven and H alehaven T r e e s D u rin g
S p rin g 1958

R edhaven

V a r ie ty

H alehaven

M a te r ia l
(A v erage n u m b e r of flow er buds p e r lin e a r foot)
NAA1
2
NPA

7 .0

12. 8

17. 0

17. 4

C on trol

11. 9

16. 1

L. S. D. 5 p e r c e n t level
1 p e r c e n t level

4. 0
5. 4

3 .8
N. S.

■'‘NAA w as ap p lied at 30 ppm 42 days a f te r bloom in 1957.
^NPA w as a p p lie d at 300 ppm th r e e days a f t e r bloom in 1957.

49.

II. F ie ld Studies C o m p a rin g N a tu ra l Blossom and F r u it Drop with
th a t R e s u ltin g fro m the u se of N ap h th alen eacetic Acid and N - l n ap h th y lp h th alam ic Acid.
The a v e r a g e daily blo sso m o r fru it drop of young R edhaven p e a c h e s
of th e c o n tro l t r e e s is r e c o r d e d in T a b le 7.

The a v e r a g e daily fru it drop on

n a p h th a le n e a c e tic a c id (NAA) t r e a t e d t r e e s a s o b s e rv e d a f te r the NAA t r e a t ­
m e n t on June 14,

is r e c o r d e d a ls o in T a b le 6.

The a v e ra g e daily fru it drop

of the c o n tr o ls and the t r e a t e d t r e e s is p r e s e n t e d as a b a r g ra p h in F ig u re 4.
As shown in F ig u re 4, the daily b lo sso m drop of the co n tro l t r e e s
w as h e a v ie s t d u rin g M ay 10 to M ay 17.

G r o s s ex am in atio n of the b lo s s o m s and

f r u i t fro m May 10 to M ay 17 r e v e a le d th a t 20 p e r c e n t of the b lo s s o m s w hich
d ro p p ed co n tain ed " d e v e lo p e d ” o v a r i e s a s la rg e a s th o se in b lo s s o m s still
p e r s i s t i n g on the t r e e .

The 80 p e r c e n t c o n s is te d m o stly of b lo s s o m s with

"undeveloped" p i s t i l s p lu s a few with no p i s ti l s at all.
a p p e a r e d to con fo rm w ith the findings of D etjen (27).

T h is f i r s t heavy drop
Also, it could be divided

into two c a t e g o r i e s a s r e p o r t e d by M u rn eek (71) for apples, c o n s is tin g of u n ­
p o llin a te d flo w e rs and of p o llin a te d flo w e rs w h e re f e rtiliz a tio n had failed to
take p la c e .
T h e s o - c a l l e d "June" drop, although showing only one p ro lo n g e d p e r io d
of heavy drop, m ay be divided into a f i r s t and second p e rio d , F ig u r e 4.

A s ig ­

n ifica n t i n c r e a s e of daily d ro p s o c c u r r e d d u rin g June 7 to 14, and th is r a t e of
d aily d rop r e m a in e d r e la tiv e ly c o n sta n t for two w eeks, the f i r s t p e rio d , when

50.

Average Daily Blossom

and Fruit Drop of Young Redhaven Peaches of the Control and Naphthaleneacetic Acid (NAA)
Treated Trees from Full Bloom to One Month Before Harvest, 1958

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Figure 4. Comparison of average daily blossom and fruit drop of the control and naphthaleneacetic
acid (NAA) treated Redhaven peach trees. Significantly different between the control and NAA
treated trees at 1 percent level**.
51.

the d aily drop i n c r e a s e d sig n ifican tly again, the second p e rio d , F ig u r e 4.
"Ju ne” drop o c c u r r e d about five w eek s a f t e r bloom, a s r e p o r t e d by H a r r o l d
(32) fo r the p e a c h v a r ie ty ,

C a rm a n .

The line of d e m a rk a tio n b etw een the

f i r s t and seco n d p e r io d of "June" drop a s found in this study w as r a t h e r h a r d to
d e te r m in e , but a p p a r e n tly took p la c e a p p ro x im a te ly 49 days a f te r bloom, June
21, 1958.

T h is a p p e a r e d to o c c u r about fo u r to five days a f t e r the tim e of

c e l l u l a r f o rm a tio n of the e n d o s p e rm (Table 10).

H a r r o ld (32) found the th i r d

p e r i o d of f r u it drop o c c u r r e d about the sev enth w eek a f te r bloom .

The d u r a ­

tion of "June" drop in th is study a p p e a r e d lo n g er than r e p o r t e d by H a r r o ld (32)
fo r the C a r m a n v a r ie ty .

T h e f r u its w hich dropped in June contained developed

se e d s, in d ic a tin g th at f e rtiliz a tio n had taken p la c e .

However, th e s e e d s w e re

b ro w n and s h riv e lle d .
The only sig n ifican t d ifferen ce betw een the daily fru it drop of the
c o n tro l t r e e s and the NAA t r e a t e d t r e e s o c c u r r e d d u rin g June 21 to 25, 4. 1 a s
c o m p a r e d to 1. 1 p e r 100 o rig in a l f ru its ; June 28 to July 2, 1. 9 a s c o m p a r e d to
5. 7; and July 1 to 5, 0. 4 a s c o m p a r e d to 3. 5 (Table 7).
NAA a p p lie d 42 days a f te r bloom at 30 ppm a p p e a r e d to delay the
seco n d p e r i o d of "June" drop t h r e e to four days (F ig u re 4).

A s im i l a r d elay in

fru it d rop w as r e p o r t e d by S tru c k m e y e r and R o b e rts (93) when NAA w as u sed
a s a thinn ing agent fo r ap ples, but the delay in fru it drop which they r e p o r t e d
l a s t e d a s long a s one o r two w eek s.

The use of NAA on p e a c h e s in th is study

d3.

did not exten d the seco n d p e r io d of ’’June" drop fo r a lo n g e r tim e than w as found
f o r the c o n tro l t r e e s .

T h is w as c o n tr a r y to the findings of K elley (44) w o rk in g

w ith p e a c h e s , and T e u b n e r and M u rn e e k (96) w o rkin g with ap p les.
A s the NPA thinning t r e a t m e n ts w e re m ade th re e days a f t e r full bloom
it s e e m e d d e s ir a b le to d e te r m in e the a p p ro x im a te tim e the b lo s s o m s o r f r u its
d ro p p ed fro m NPA t r e a t e d R edhaven t r e e s .

To a c c o m p lis h this, counts w e re

m ad e of b lo s s o m s and f r u its on tagged b r a n c h e s at the tim e of bloom, and a t
two and ten w eeks a f t e r bloom .

It w as found that 88. 2 p e r c e n t of the o rig in a l

n u m b e r of b lo s s o m s at full bloom had d ropped d u rin g the p e r io d of 14 days a f te r
bloom w ith the m a j o r i t y of drop o c c u r r i n g in the la s t sev en days.

W hereas,

d u rin g th is s a m e p e r io d of 14 days, it w as found that about 30 p e r c e n t of the
o r ig in a l n u m b e r of b lo s s o m s had dropped fro m the co ntro l t r e e s .

T h is p e r io d

of heavy b lo ss o m drop on both the co n tro l and t r e a t e d t r e e s coin cided w ith the
tim e of the f i r s t heavy b lo sso m drop of the co n tro l t r e e s of Redhaven in the NAA
study ( F ig u re 4).
As s ta te d p r e v io u s ly M u rn e e k (71) su g g ested that the f i r s t heavy drop of
a p p le s could be divided into two c a te g o r ie s c o n s is tin g of unp ollin ated flo w e rs and
of p o llin a te d f lo w e rs w h e re f e r tiliz a tio n had failed to take p la c e .

On the b a s is of

th is, a s s u m i n g that the p o llin atio n should stim u la te the grow th and developm ent
of the p i s t i l (77), the flo w e rs w hich fell d u rin g the f i r s t heavy drop fro m n on ­
t r e a t e d c o n tro l t r e e s and the NPA t r e a t e d t r e e s of Redhaven w e re e x am in ed to

o4.

d e t e r m in e the n u m b e r w hich had b een p o llin ated and th o se w hich w e r e unpollinated.
E x a m in a tio n s of the flo w e rs fro m the NPA t r e a t e d t r e e s r e v e a le d that 65. 5 p e r c e n t
of th o se w hich had dro p p ed co ntained a "developed" p is til.

W h ereas, fo r the c o n ­

t r o l t r e e s it w as found th at only 19. 8 p e r c e n t of the flo w e rs which d ro p p ed c o n ­
ta in e d a "develo ped" p is t i l.

T h is would in d icate that the n u m b e r of p o llin a te d

f lo w e rs w hich had a b s c i s s e d d u rin g th is p e r io d of drop w as in c r e a s e d by NPA
t r e a t m e n t m ad e t h r e e days a f t e r bloom on Redhaven p e a c h t r e e s .

A sim ila r r e ­

s u lt w as found fo r NPA t r e a t e d H alehaven t r e e s a s 83. 3 p e r c e n t of the b lo s s o m s
w hich had a b s c i s s e d co n tain ed a "developed" p is til as c o m p a re d to only 20. 0 p e r ­
c en t fo r the c o n tro l t r e e s .
In o r d e r to d e te r m in e if f e rtiliz a tio n had taken p la c e in the flo w e rs which
had d ro p p ed fro m R edhaven t r e e s t r e a t e d with NPA, the ovules of ten of th e s e
f lo w e rs w e r e e x a m in e d u n d e r the m ic ro s c o p e .

No m o re than eight nu clei w e re

found w ithin the e m b ry o s a c of any one of th e s e ovules.

In c o m p a riso n , 14 nu clei

w e re found in the e m b ry o s a c s of flo w e rs still r e m a in in g on the u n tre a te d c o n tro l
tre e s.

T h is would in d icate th at f e r tiliz a tio n had not taken p la c e in "developed"

p i s t i l s of the flo w e rs w hich had a b s c i s s e d from the Redhaven t r e e s t r e a t e d with
NPA o r th a t the zygote faile d to develop.

III. A n ato m ical In v estig atio n s of the D eveloping E m b ry o and
E n d o s p e rm of H alehaven and Redhaven P each
The p r o g r e s s i v e grow th and d evelopm ent of the em bryo, en d o s p e rm ,
s e e d and p e r i c a r p of the H alehaven p e a c h from full bloom th ro u g h the p e r io d
of "June" drop in 1957 and 1958 and of the Redhaven p e a c h in 1958 a r e r e c o r d e d
in T a b le s 8, 9 and 10.

G row th of the em bryo, the e n d o sp e rm , the se e d and

the p e r i c a r p in len gth is p lo tted a g a in s t days in F ig u r e s 5 and 6 for the H a le ­
h av en p e a c h in 1957 and 1958, and in F ig u re 7 fo r the Redhaven p e a c h in 1958.
T he data of the tim e of c e ll u l a r fo rm a tio n of the en d o sp erm of H aleh aven and
R edh aven p e a c h e s in 1958, a s a n aly zed fro m whole m ounts, a r e given in
T a b le 11.
M ic r o s c o p ic ex a m in a tio n s of o vules of Redhaven p e a c h b lo s s o m s c o l ­
le c te d a t full bloom, May 3, 1958, r e v e a le d a p p ro x im a te ly th re e nuclei w ithin
a m e g a s p o r e (Table 10).

F o u r and seven days a f te r bloom, about six and eight

nuclei w e r e lo c a te d within the m e g a s p o re tis s u e (Table 10).

In the co llectio n

m ad e s e v e n days a f t e r bloom, th r e e nuclei, the antipo dals, w e r e o b s e r v e d at
the d is til end; t h r e e nuclei, the s y n e rg id s and the egg; at the m i c r o p y l a r end
and one o r two nu clei, the e n d o s p e rm nucleus, a t the c e n t e r of the e m b ry o sac.
Syngam y a p p a r e n tly took p la c e in the Redhaven p each betw een May 10
and M ay 17, 1958, 7 to 14 days a f t e r bloom.

F ro m o b s e rv a tio n s of c e r t a i n

s lid e s , the zy go te had not divided in m o s t c a s e s by May 17, but m any e n d o ­
s p e r m nu clei, about 14 in n u m b er, a p p e a r e d w ithin the em b ry o sac (Table 10).

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59.

P e r ic a r p

1000

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25
20

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T ree-n u clear
Endosj^grm
** C e llu la r
E nd osp erm

500

200
100
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24
M ay

14 17 21 24 28
June

F ig u r e 5. G row th of the em bry o, en d o sp erm , seed and p e r i c a r p of
the young H alehaven p e a c h from full bloom thro ug h "June" drop,
1957. G row th w as d e te r m in e d by lin e a r m e a s u r e m e n ts in m i l l i ­
m e t e r s , ex cep t e m b ry o length in m ic ro n s .

Embryo Length (microns)

Length (m illim eters)

40

60.

E m b ry o
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June

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500

200

Embryo length (microns)

40

100
0

28

F ig u r e 6. G row th of the em bry o, en d o sp erm , s e e d and p e r i c a r p of the young
H alehaven p e a c h d u rin g ’’June” drop, 1958. Growth w as d e te rm in e d by
l i n e a r m e a s u r e m e n t s in m i l l im e t e r s , except e m b ry o length in m ic ro n s .

1000

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200
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0

28
June

100

July

F ig u r e 7. G ro w th of the em bry o, e n d o sp erm , s e e d and p e r i c a r p of the young
R edhaven p e a c h fro m full bloom through "June" drop, 1958. G row th w as
d e te r m in e d by l i n e a r m e a s u r e m e n t s in m i ll i m e t e r s , ex cep t e m b ry o length
in m i c r o n s .

Embryo Length (microns)

E m b ry o
40

61.

The m ic r o s c o p i c s e c tio n s of H alehaven p each ovules of 1957 c o lle c te d d u rin g
the f i r s t w eek a f te r bloom w e r e stain ed too heavy to study p o s s ib le m e g a g a m e to g e n e s is .
The p r e s e n c e of a zygote within the em b ry o sac w as o b s e rv e d f i r s t
in H aleh av en p e a c h s e e d s c o lle c te d M ay 13, 1957, about 11 days a f t e r bloom
and f i r s t d iv isio n of the zygote o c c u r r e d within four days (Table 8).

In 1958,

w o rk in g w ith the Redhaven v a r ie ty the zygote was f i r s t o b s e rv e d on May 17,
14 days a f t e r bloom (T ab le 10); and in som e c a s e s f i r s t div ision of the zygote
had a lr e a d y tak en p la c e (F ig u re 8).

H a r ro ld (32) studying the p each v a rie ty ,

C a rm a n , o b s e rv e d zygote d ivision 12 days a f te r bloom, while D o rsey w o rk in g
w ith the E l b e r ta p e a c h (28) found the zygote division to o c c u r about 27 days
a f t e r bloom .

The p each e m b ry o of both H alehaven and Redhaven v a r i e t ie s

grew v e r y slow in length, width and cell n u m b e r fo r a p p ro x im a te ly 42 days
a f t e r the f i r s t d ivision ( F ig u r e s 5 and 7).
An a tte m p t w as m ad e to c la s s if y the d ev elopm ental stag e of the p each
e m b ry o a s r e p o r t e d by M e y e r (67) for the em b ryo of the developing M cIn to sh
apple.

M e y e r c la s s if ie d th r e e s ta g e s of p ro e m b ry o developm ent fro m the tim e

of f i r s t c e ll d iv isio n to the stag e of cotyledon developm ent as filam en to u s,
s p h e r i c a l and t r a n s itio n a l.

He d e s c rib e d the filam en to u s stag e a s follows;

" T h e e m b ry o beginning with the f i r s t cell division grow s and divides as a
l i n e a r o b ject. " The fila m e n to u s stag e of the p e a c h e m b ry o is e x em p lified in

F ig u re 8
T w o -c e lle d e m b ry o found in the Redhaven p e a c h on M ay 17, 1958,
14 days a f t e r bloom. The em b ry o is in the e a r l y fila m e n to u s stag e .
The en d o s p e rm is in the f r e e - n u c l e a r stag e. (X510)

F ig u re 9
A typ ical em b ry o found in the Redhaven p e a c h on June 11, 1958,
39 days a f t e r bloom. The em b ry o of a p p ro x im a te ly 56 c e lls is the late
filam en to u s stag e. T he e n d o s p e rm is in the f r e e - n u c l e a r stag e . (X200)

F ig u r e 10
The en d o s p e rm found in the Redhaven p e a c h on June 14, 1958,
42 days a f t e r bloom. C e llu la r f o rm a tio n of the e n d o s p e rm h a s begun
at the m i c r o p y l a r end and the p e r ip h e r y of the e m b ry o sac. (X200)

F ig u re 11
A typical e m b ry o found in the R edhaven p each on June 18, 1958,
46 days a f te r bloom. The e m b ry o of a p p r o x im a te ly 95 c e l l s is in the
s p h e ric a l stag e. The e n d o s p e rm h as changed from the f r e e - n u c l e a r
s ta te to the c e l l u l a r condition. (X200)

62.

63.

F i g u r e s 8 and 9.

In 1957 the em b ry o of the H alehaven p each could be c l a s s i ­

fied a s fila m e n to u s fo r a p p ro x im a te ly 28 days fro m about 15 to 43 days a f te r
bloom (T able 8).

In 1958 the Redhaven p each em b ry o w as found a ls o to be

f ila m e n to u s fo r a 2 8 -d ay p e r io d beginning 14 days a f t e r bloom (Table 10 and
F ig u r e 9).

M e y e r (67) found that th is em b ry o stag e la s te d only 10 days fo r

the M cIntosh apple.
The second stag e a s d e s c rib e d by M ey er (67), the s p h e ric a l stag e of
th e em b ry o , begins when the d istil t i e r s of c e lls i n c r e a s e in s iz e in t h r e e d im e n ­
s io n s.

T h is sta g e of the p e a c h em b ry o is shown in F ig u re s 11 and 12.

In 1957

th is sta g e w as o b s e rv e d about 43 days a f t e r bloom for the H alehaven v a r ie ty
and continued fo r 7 to 10 days, T ab le 8, and in 1958 th is s p h e ric a l stag e w as
o b s e r v e d about 39 days a f t e r bloom and la s te d 7 to 10 days (Table 9).

For

the R edh av en v a r ie ty , the s p h e r ic a l stag e began about 42 days a f t e r bloom
and continued fo r 7 to 10 days (Table 10).

F o r both the Redhaven and H alehaven

th is stag e w as found to begin about th r e e o r four days b efo re e n d o sp e rm c e l lu ­
l a r fo rm a tio n .

M e y e r (67) o b s e r v e d th at the s p h e ric a l stag e of the e m b ry o of

the M cIn to sh apple began about 22 days a f t e r f e rtiliz a tio n and la s te d fo r nine
days.
T he tra n s itio n a l stag e o r the th ird stage of em b ry o developm ent m a r k e d
by the e lip itic a l d ev elo p m en t of the d istil p o rtio n of the em b ryo , a p p e a r e d f i r s t
when the e m b r y o s of the R edhaven and H alehaven re a c h e d about the 300- to 500-

64.

c e lle d sta g e ( F ig u r e 13).

By th is tim e the e m b ry o of both p e a c h v a r i e t i e s had

a tta in e d a l i n e a r d im en sio n of 100 m ic r o n s in 1957 and 1958 (T ab les 8, 9 and 10).
T h is change took p la c e in the H alehaven v a r ie ty about 49 days a f te r full bloom
in both 1957 and 1958.

T h is change in developm ent of the Redhaven e m b ry o

w as about 49 to 53 days a f t e r bloom c o m p a rin g c lo s e ly with th a t of the H a le ­
h aven v a r ie ty .

The change fro m the s p h e ric a l to the tra n s itio n a l stag e o c c u r r e d

fo r both p e a c h v a r i e t i e s about th r e e o r four days a f t e r the co m p lete change of
the e n d o s p e rm fro m f r e e - n u c l e a r to c e llu la r fo rm atio n (T ab les 8, 9, 10 and 11).
C oinciding with the change to the tra n s itio n a l stag e w as the g rad u al
i n c r e a s e d ra p id r a t e of grow th in length, width, and cell division of the H a le ­
h aven and Redhaven e m b r y o s .

However, the high est r a t e of em b ry o grow th

w as found to o c c u r d u rin g the te r m in a tio n of the tra n s itio n a l stag e (F ig u re 14)
and the in itia tio n of the co ty led o n ary stage (F ig u re 15).
days a f t e r in itia l t r a n s i t i o n a l developm ent.

T h is w as about seven

To e x p r e s s th is in a d iffe re n t way,

the r a p id grow th of the e m b ry o took p la c e about 10 days a f t e r c e llu la r fo rm a tio n
of the e n d o s p e rm (T ab les 8, 9, 10 and 11).
In g e n e ra l, the tim e of in itiatio n of the ra p id grow th of the p e a c h em b ry o
a s found in th is study a g r e e s with T u k e y ’s o b s e rv a tio n s of v a rio u s v a r i e t i e s of
p e a c h e s (98).

He c l a s s i f ie d th is change in grow th r a te a s Stage II, w hich begins

w ith the ra p id dev elo p m en t of the p e a c h em bryo, about 49 days a f t e r bloom.
E n d o s p e rm d evelopm ent of both the H alehaven and Redhaven f r u its

F ig u re 12
A ty p ical e m b ry o found in the R edhaven p e a c h on June 21, 1958,
49 days a f t e r bloom . The e m b ry o is in the late s p h e r ic a l stag e . T he
e n d o sp e rm has changed fro m the f r e e - n u c l e a r sta te to the c e ll u l a r
condition. (X93)

F ig u r e 13
A typ ical e m b ry o found in the H alehaven p e a c h on June 21, 1957,
49 days a f t e r bloom . The em b ry o is in the e a r l y tr a n s i ti o n a l stag e.
The e n d o s p e rm h a s changed fro m the f r e e - n u c l e a r stag e to the c e llu la r
condition. (X93)

F ig u r e 14
A typ ical e m b ry o found in the R edhaven p e a c h on June 28, 1958,
56 days a f t e r bloom. The e m b ry o is in the late tr a n s i t io n a l stage, the
co ty led o n ary p r i m o r d i a showing. T he e n d o s p e rm h as chan ged fro m the
f r e e - n u c l e a r sta te to the c e llu la r condition. (X46)

F ig u re 15
A ty pical e m b ry o found in the H alehaven p each on June 28, 1958,
57 days a f t e r bloom . T he e m b ry o is in the co ty le d o n a ry stag e . T h e
e n d o s p e rm h a s changed fro m the f r e e - n u c l e a r s ta te to the c e l l u l a r c o n ­
dition. (X46)

65.

F ig u r e 12

F ig u re 13

F ig u r e 14

F ig u re 15

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w as v e r y r a p id im m e d ia te ly a f t e r syngamy, the developm ent p r i m a r i l y m a n i ­
f e s te d a s m an y d iv isio n s of the f r e e - n u c l e i .

A p p ro x im a te ly 14 nuclei w e r e

found w ithin e m b ry o sac of the Redhaven peach c o lle c te d May 17, 1958 (Table
10) a t the tim e of zygote division.

The tim e of the f i r s t division of e n d o s p e rm

n u cleu s, 7 to 14 days a f te r bloom, a g r e e s c lo se ly with H a r r o l d ’s study of the
C a r m a n p each.
T he r a t e of c e ll d ivision of the em bryo in the Redhaven v a r ie ty was
h ig h e r than the e n d o s p e rm n u c le a r d ivision d u rin g the p e r io d May 17 to 24.
The change was one to 15 c e lls for the em b ry o a s c o m p a re d to 14 to 90 nuclei
of ihe e n d o s p e rm (T able 10).

F u r th e r m o r e , 14 days a f t e r the f i r s t evid en ce of

an e n d o s p e rm , m ic r o s c o p ic stu d ies re v e a le d that the e m b ry o sac contained a s
m a n y a s 400 e n d o s p e rm nuclei a s c o m p a re d to about 27 c e lls fo r the em b ry o .
D u ring the p e r io d of 21 days a f te r the f i r s t a p p e a ra n c e of the en do ­
s p e rm , the e m b ry o s ac of both H alehaven and Redhaven developed ra p id ly in
length to w a rd the c h a la z a l po cket of the ovule (T ab les 8 and 10) and the en do ­
s p e r m a p p e a r e d to occupy the e n t ir e a r e a of the em b ry o s a c d u rin g th is lengthen
ing p r o c e s s .

T he ex ten sio n of the em b ry o sac to the c h alazal pocket a p p a re n tly

w as co m p lete 35 days a f t e r bloom fo r H alehaven in both 1957 and 1958 and for
R edh aven in 1958 ( F ig u r e s 7, 8 and 9).
The change of the e n d o s p e rm fro m the f r e e - n u c l e a r sta te to c e llu la r
fo rm a tio n in the H alehaven p e a c h in both y e a r s a p p e a re d about 42 days a f te r
bloom and w as a p p a r e n tly c o m p le te within two o r th re e days (Tables 8, 9 and 11)

68.

T h is change fo r the R edhaven v a r i e t y w as v e ry s im i l a r to the H alehaven,
o c c u r r i n g 44 to 45 days a f t e r full bloom (T ables 10 and 11).

H a r r o ld (32)

found a ls o that the e n d o s p e rm r e m a in e d in a f r e e - n u c l e a r sta te until the end
of the six th week, 42 days a f te r bloom.
Long thin s tr a n d s of cy top lasm a p p e a re d throughout the f r e e - n u c l e a r
e n d o s p e rm of H aleh aven and Redhaven a w eek befo re fo rm a tio n of the cell
w a lls with the g r e a t e s t c o n c e n tra tio n of th ese s tr a n d s s u rro u n d in g la rg e v a c u o ­
la te d a r e a s n e a r the m ic r o p y l a r end of the en d o sp erm ( F ig u re s 9, 10 and 11).
G ra d u a l f o rm a tio n of the c e ll c a lls a p p e a r e d at the m ic r o p y la r end a t the p e r i ­
p h e r y of the e m b ry o s a c and continued until the la rg e vacoule in the c e n te r
b e c a m e c o m p le te ly occupied w ith c e lls.

Tukey (97) d e s c rib e d a s im i l a r d e ­

v e lo p m e n t in the c e l l u l a r f o rm a tio n of the e n d o sp e rm of the sw eet c h e r ry ,
P ru n u s avium .
Im m e d ia te ly a f t e r en d o s p e rm c e llu la r form ation, the e n d o sp e rm of
the H aleh av en and R edhaven p e a c h grew v e r y ra p id ly in length and width
(T ab les 8, 9 and 10) r e a c h in g about o n e - th ir d the volum e of the seed 18 days
a f t e r c e l l u l a r fo rm a tio n .
C oincident w ith this, the r a t e of grow th of the se e d and p e r i c a r p of
the H aleh av en and R edhaven p each declined sh arp ly .

T h is change in grow th r a t e

o c c u r r e d sev en to eight w eeks a f t e r full bloom, d u rin g the 1958 s e a so n ( F ig u r e s
8 and 9) and it followed a v e r y s i m i l a r grow th p a tte r n as found fo r the H alehaven

in 1957 ( F ig u r e 7).

T h e s e gro w th r e la tio n s w e r e d e s c rib e d by Tukey (98) in

a n e a r l i e r study of the grow th and developm ent of the p each.
The e n d o carp of both the H alehaven and Redhaven of 1958 w e r e found
to begin to h a r d e n about 35 days a f te r bloom, m akin g it difficult to b r e a k the
p e r i c a r p in half w ith the fin g e rs .

By 56 days a f te r bloom the en d o carp w as

too h a r d f o r p e n e tr a tio n of even a r a z o r blade.
T he te r m " sh u ck -o ff" is used freq u en tly in re la tio n to p e a c h e s and
m e a n s the shedding of the hypanthium from the young fru it.

T he hypanthium

u n ites the s ta m e n s , c h o ro lla and calyx to the r e c e p ta c le of a p e rig y n o u s
flo w er.

M o st of the shucks w e re shed fro m H alehaven p e a c h e s in 1957 about

30 to 32 d ays a f t e r bloom.

W h ereas, the g r e a t e s t p o rtio n of " sh u c k -o ff" from

both H alehav en and R edhaven p e a c h e s in 1958 o c c u r r e d a p p ro x im a te ly 29 days
a f t e r bloom .

E n d o s p e rm c e l l u l a r fo rm atio n o c c u r r e d a p p ro x im a te ly 12 days

a f t e r " s h u c k -o ff" for H alehav en in 1957, 15 days a f te r "sh u ck -off" fo r H a le ­
haven in 1958, and 18 days a f t e r "sh uck -o ff" for Redhaven in 1958.

It m ight

be that the tim e of "sh u ck -o ff" fo r a sp ecific v a r ie ty could be u se d to d e t e r ­
m in e the a p p r o x im a te tim e th a t the e n d o sp erm of the p e a c h changed fro m a
f r e e - n u c l e a r s ta te to c e llu la r fo rm .

70.

IV. N a tu ra l H orm o ne Content and C o n cen tratio n of Young Redhaven
P each Seeds a s R elated to E a rly Growth and D evelopm ent.
Studies in 1957 r e v e a le d that the en d o sp erm of the H alehaven s e e d s
changed fro m a f r e e - n u c l e a r s ta te to a c e llu la r sta te a p p ro x im a te ly six w eeks
a f t e r bloom .

T h e re f o re , s tu d ie s w e r e set up to ev aluate the n a tu r a l h o rm on e

con ten t and c o n c e n tra tio n of the s e e d s before, during, and a f te r the e n d o s p e rm
b e c a m e c e llu la r .
T he g row th r e s p o n s e s u sin g the avena s tra ig h t grow th te s t by t r e a t ­
ing 5 m i l l i m e t e r s e c tio n s of Brighton o ats with diethyl e th e r e x t r a c ts of young
R ed hav en p e a c h s e e d s and with v a rio u s c o n c e n tra tio n s of in d o leacetic a c id (IAA)
and of ethy l in d o le a c e ta te (EtIA) a r e r e c o r d e d in Table 12.

A s u m m a r y of the

d ata of n a tu r a l h o rm o n e content and co n cen tratio n from diethyl e th e r e x tr a c ts
of young R edhaven p e a c h s e e d s a s d e te rm in e d by the aven a s tr a ig h t grow th
t e s t s shown in T a b le 12 a r e r e c o r d e d in T able 13.

The c a lc u la te d c o n c e n t r a ­

tion and con ten t of h o rm o n e s p r e s e n t in the s e e d s a r e p lo tte d a g a in s t tim e s
of s a m p lin g s in F ig u r e s 16 and 17.

The acid and the n e u tra l fra c tio n s of the

June 15 diethyl e t h e r e x t r a c t w e re c h ro m a to g ra p h e d u sin g a 8:1:1 volu m e r a tio
of 2 -p ro p a n o l, am m o n ia, and w a te r solvent, and the se c tio n s of the c h r o m a t o ­
g r a m s w e r e a n a ly z e d by the av en a s tr a ig h t grow th te s t.
c o r d e d in T a b le 14.

T h e se data a r e r e ­

T he data of the c h r o m a to g ra m s a r e p lo tted as h is to g r a m s

in F i g u r e s 18 and 19.
T he n a tu r a l h o rm o n e content from the acid and n e u tra l f ra c tio n s of

71.

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N —-

A 0. 05 milliliter dilution of each fraction of the diethyl ether extract was used in the avena tests and also in
making these tabulated calculations.

Summary Data of Natural Hormone Content and Concentration from Diethyl Ether Extracts of Redhaven
Peach Seeds as Determined by the Avena Straight Growth Test^

72.

F ig u re 16
N atu ral h o rm o n e c o n c e n tra tio n fro m diethyl e t h e r e x t r a c t s of
R edhaven p each a s d e te r m in e d by the av en a s tr a ig h t grow th te s t, 1958.
H orm one c o n c e n tra tio n of the a c id f r a c tio n of the e x t r a c t is com p uted
in equ ivalent in d o leacetic a c id (1AA) m i c r o g r a m s p e r g ra m f r e s h w eight
of s e e d s. H orm one c o n c e n tra tio n of the n e u tr a l f r a c tio n is com pu ted in
ethyl in d o le a c e ta te (EtIA) m i c r o g r a m s p e r g r a m f r e s h w eight of s e e d s .

F ig u r e 17
N atu ral ho rm o n e content from diethyl e t h e r e x t r a c t s of R edhaven
p e a c h s eed s as d e te r m in e d by the avena s tr a ig h t grow th te st, 1958. H o r ­
m one content of the a c id fra c tio n of the e x t r a c t is com p uted in equ ivalent
in d o leacetic a c id (LAA) m i c r o g r a m s in s e e d s of 100 f r u i t s . H orm on e
content of the n e u tr a l f ra c tio n of the e x t r a c t is co m p u ted in eq u iv alen t
ethyl in d o le a c e ta te (EtIA) m i c r o g r a m s in s e e d s of 100 f ru its .

Hormone Concentration (Micrograms per Gram
Fresh Weight of Seeds)

.5

Hormone Content (Micrograms in Seeds
of 100 Fruits)

73.

8.0

Acid fraction (equiv. IAA)
Neutral fraction (equiv. EtIA)

.4

.3

.2

.1

0

2
June

7
June

15
June

28
June

21
June

A cid fraction (equiv. IAA)
Neutral fraction (equiv. EtIA)

7 .0

6.0
5 .0
4 .0
3 .0

s

\

2.0
1.0
0.0

2
June

7
June

15
June

21
June

28
June

74.

the e x t r a c t s of young Redhaven p e a c h s e e d s sam p led on June 2, 7, 15, 21 and
28 a s d e te r m in e d by the avena s tr a ig h t grow th t e s t w as sign ifican tly h ig h e r
th an the c o n tro l t r e a t m e n ts of the pho sph ate buffer solution fo r all sam p lin g
d a te s w ith one exception, the acid f ra c tio n of June 2 (Table 12).

The n a tu ra l

h o rm o n e content of the s e e d s of both the acid and n e u tra l f ra c tio n s r e a c h e d a
m a x im u m in quantity of June 15 (F ig u re 11).

The co n cen tratio n of the n a tu ra l

h o rm o n e in the s e e d s w as h ig h e st on June 15 fo r the acid fra c tio n of the e x ­
tra c t.

W h ereas, the ho rm o n e c o n cen tratio n of the n e u tra l fra c tio n w as high est

on June 7.

The n a tu r a l h o rm o n e co n c e n tra tio n of the n e u tra l f ra c tio n w as

r e l a t iv e ly the s a m e for the f i r s t th r e e d ates of sam pling, June 2, 7 and 15,
a f t e r w h ich tim e it d e c r e a s e d m a rk e d ly .

D uring the p e rio d the weight of the

s e e d of 100 f r u i t s in c r e a s e d fro m 2. 8 g r a m s on June 2 to 46. 6 g r a m s on June
28 (Table 13).

T he h o rm o n e c o n c e n tra tio n and content p r e s e n t in the acid

fr a c tio n had a g r e a t e r v a r ia tio n d u rin g the p e r io d of s a m p lin g than was found
fo r the n e u tr a l f r a c tio n ( F ig u r e s 16 and 17).
It w as o b s e rv e d th at the dilution q u an tities of 0. 5 and 1. 0 m i l l i l i t e r
of the a c id and n e u tr a l f ra c tio n s fro m e x tr a c t s of Redhaven p e a c h se e d s c o l ­
le c te d June 2 and 7 a lm o s t c o m p le te ly inhibited any grow th of co leoptile.

The

only e x c e p tio n w as the 0. 5 m i l l i m e t e r of the n e u tra l fra c tio n from the June 7
c o lle c tio n w hich re d u c e d the grow th of the coleoptile in c o m p a ris o n to the
c o n tro l of p h o sp h ate buffer solution alone.

75.

C oinciding c lo s e ly w ith the o b s e rv e d high ho rm o n e acc u m u la tio n in
the p e a c h s e e d s on June 15, w as the g rad u al change of the e n d o sp erm fro m a
f r e e - n u c l e a r s ta te to a c e l l u la r condition which took p lace in 1958 fo r the
R edhaven v a r i e t y fro m a p p ro x im a te ly June 14 to June 18.

Luckw ill (57) a lso

found a c lo s e c o r r e l a t i o n betw een high horm o ne content of the s e e d s of the
Beauty of Bath apple and the tim e of c e llu la r fo rm a tio n of the e n d o s p e rm .

He

b e lie v e d the lo catio n of the n a tu ra l h o rm o n e m ay be in the e n d o sp e rm sin ce the
n u c e llu s w as a lm o s t c o m p letely a b s o rb e d by the e n d o sp erm at the tim e he m ad e
th e s e o b s e rv a tio n s .

By c o n tr a s t, the Redhaven p each e n d o sp erm did not a p p e a r

to be any l a r g e r than o n e -te n th the s iz e of the nu cellu s a t the tim e of the la s t
sam p ling , June 28.
High daily r a te of fru it drop of Redhaven, com m only r e f e r r e d to as
"June" drop, betw een June 21 and June 28,

1958 a p p e a re d a f t e r the high c o n ­

c e n tr a tio n and content of n a tu r a l h o rm o n e s of the p each s e e d s o b s e rv e d June
15 ( F ig u r e s 4, 16 and 17).
(58) w o rk in g with the apple.

T his did not conform with the findings of Luckw ill
He r e p o r te d that high h o rm o n e content of apple

s e e d s c o r r e s p o n d e d w ith the te r m in a tio n of the "June" drop.
As the a v en a s tr a ig h t grow th t e s t s re v e a le d the p r e s e n c e of n a tu ra l
o c c u r r i n g h o rm o n e s in the seed, stu d ies w e re m ade in hopes of identification.
D r ie d c h r o m a to g ra p h e d p a p e r s which had been spo tted w ith 0. 05 m i l l i l i t e r of
the n e u tr a l fra c tio n and of the a c id fra c tio n of the se e d e x t r a c t s of the June 15

76.

s a m p le w e r e s c a n n e d w ith a 2537 " M in e ra lig h t" for u ltra v io le t ab s o rp tio n .
ligh t blue spot w as found at Rf

1

A

0. 89 on the c h ro m a to g ra p h p a p e r of the

n e u tr a l fra c tio n , but no n o ticeab le spot w as o b s e rv e d on the c h ro m a to g ra p h
p a p e r of the a c id f ra c tio n .
C h ro m a to g ra p h p a p e r s w e r e spotted with EtIA and with IAA in the
so lv en t 8:1:1 vo lu m e r a tio of 2 -p ro p an o l, am m o n ia and d istille d w a te r, dried,
and s c a n n e d w ith the " M in e ra lig h t" a s fo r the n e u tra l and a c id f ra c tio n s of
the p e a c h s e e d e x t r a c t s .

A blue spot was found fo r the c h ro m a to g ra p h e d

EtIA at Rf 0. 91, and a white spot w as evident for the c h r o m a to g ra p h e d IAA
at Rf 0. 50.
F o r f u r t h e r ev alu atio n th e s e c h r o m a to g ra m s of the acid and n e u tra l
f r a c tio n s co n tain in g the n a tu r a l e x tr a c te d h o rm o n e s w e r e cut into s tr i p s and
b io lo g ic a lly a s s y e d w ith the avena s tr a ig h t grow th te s t.

G row th r e s p o n s e s

w e r e o b s e r v e d a t the Rf r a n g e s of 0. 5 to 0. 6, 0. 6 to 0. 7, and 0. 7 to 0. 8 for
the a c id f r a c tio n and of 0. 8 to 0. 9 and 0. 9 to 1 .0 fo r the n e u tra l fra c tio n
(Table 14 and F i g u r e s 18 and 19).

T he Rf of th e se grow th r e s p o n s e a r e a s

would be about 0. 63 for the acid fractio n , and 0. 93 fo r the n e u tr a l f ra c tio n
the m id - p o in ts of e a c h Rf spot.
Sen and L eap o ld (86) have r e p o r te d the use of E r l i c h e r ’s r e a g e n t to
d e t e r m in e the p r e s e n c e of indole com pounds.

A ccordingly,

E r l i c h e r 's re a g e n t

1Rf is the d ista n c e the s u b sta n c e m ig ra te d , divided by the d ista n c e the s o l ­
v en t fro n t m ig ra te d .

The Summary Data on the Chromatographed Paper of Diethyl Ether Extracts of Redhaven Peach Seeds Using 2Propanol, Ammonia, Water (8:1:1 v/v) Solvent and Determined by Avena Straight Growth Test

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79 .

w a s s p r a y e d on c h r o m a to g ra p h p a p e r s of the n e u tra l and acid f ra c tio n of the
e x t r a c t e d h o rm o n e s .

No n o tic e a b le spot w as fo rm e d on the c h r o m a to g ra p h

p a p e r of the a c id f r a c tio n t r e a t e d w ith E r l i c h e r 's re a g e n t.

However, a

light blue sp ot w as lo c a te d on c h ro m a to g ra p h p a p e r of the n e u tra l fra c tio n .
C h ro m a to g ra p h p a p e r s of EtIA and IAA w e re a ls o t r e a t e d w ith E r l i c h e r 's
r e a g e n t.

A blue spot w as found a t Rf 0. 95 on the EtIA p a p e r, while an

o ra n g e spot w a s evid ent at Rf 0. 50 on the IAA p a p e r.
On the b a s is of th e s e ev alu atio ns, it a p p e a rs that the n a tu r a l h o r ­
m o n e p r e s e n t in the a c id f ra c tio n of the e x tr a c tio n fro m the Redhaven p e a c h
s e e d s is not IAA.

T h e r e is a s tr o n g indication, however, th at the n a tu ra l

h o rm o n e p r e s e n t in the n e u tr a l fra c tio n of the e x tra c tio n is EtIA.

80.

DISCUSSION

Two p la n t r e g u la to r s , N - 1-naph thy lph thalam ic acid (NPA) and napht h a le n e a c e tic a c id (NAA), when ap p lied to p each t r e e s th re e and 42 days a f t e r
bloom, r e s p e c tiv e ly , at the c o r r e c t c o n c e n tra tio n have sign ificantly re d u c e d
the f ru it se t a s w as found in th is study.

But it has been o b s e rv e d that NPA

a p p lic a tio n s to p e a c h t r e e s l a t e r than seven days a f te r full bloom do not r e ­
duce the f r u i t s e t (2).

W h ereas, H ibbard and M urneek (33) and K elley (44)

have found that an ap p licatio n of NAA at low c o n c e n tra tio n s does not r e s u l t
in e ffectiv e f r u it thinning when applied to p each t r e e s d u rin g a p e r io d of a p ­
p r o x im a te ly 30 days following bloom.

T h e re fo re , it is a p p a re n t th at the

a p p lic a tio n of the two m a t e r i a l s a r e effective in re d u c in g the se t of b lo ss o m s
and f r u i t s from p e a c h t r e e s at two d ifferen t developm ental s ta g e s of the
r e p ro d u c tiv e o rg an .

A h isto lo g ical study of the developing flow er and fru it

w as t h e r e f o r e n e c e s s a r y to e s ta b lis h the stage of developm ent d u rin g which
the a p p lic a tio n of th e s e m a t e r i a l s to p e a c h t r e e s would r e s u l t in effective
thinning.
O vules of Redhaven p e a c h e s w e re exam ined a n a to m ic a lly a t full
bloom, a t four, and a t sev en days a f t e r bloom in 1958.

F ro m th e se e x a m in ­

atio n s, it w as o b s e r v e d that m e g a g a m e to g e n e s is w as in p r o g r e s s in the p each
ovule d u rin g the sev en day p e r io d a f te r bloom (Table 10).

Syngamy did not

tak e p la c e in the p e a c h e s of the Redhaven t r e e s u sed in th is study in 1958

until d u r in g a s e v e n -d a y p e r io d betw een seven and 14 days a f te r bloom (Table
10).

T h is c o n fo rm e d w ith the findings of H a r ro ld (32) who r e p o r te d that syn-

gam y took p la c e about nine days a f t e r bloom in the p each of the C a rm a n
v a r ie ty .
The NPA ap p lic a tio n s m ade th re e days a f te r bloom on young R e d ­
hav en t r e e s sig n ific a n tly re d u c e d the n u m b er of b lo s s o m s in 1958 (T able 10).
T h is is a s tr o n g indication, th e r e fo r e , that the p r o c e s s by which p each
flo w e rs a r e re m o v e d by the r e s u l t of an NPA application m ay involve the
p r e v e n tio n of syngam y.

S im ila rly , Luckwill (62) has o b s e rv e d that NAA

s p ra y e d on open apple flo w ers b efore po llination induced in co m p atib ility b e ­
tw een p o lle n tu b es and s ty la r tis s u e , and th e r e f o r e has s u g g ested that th is
m a y a cco u n t fo r thinning actio n of NAA when applied at th is stage.
F u r t h e r evidence to su p p o rt th is hy po thesis of p e a c h thinning w ith
NPA w as found by o b s e rv in g the n u m b e r and type of b lo s s o m s which dropped
fro m the NPA t r e a t e d t r e e s .

A m uch g r e a t e r n u m b er of b lo s s o m s drop ped

fro m the NPA t r e a t e d t r e e s than fro m the co n tro l t r e e s d u ring the f i r s t heavy
daily d rop of b lo s s o m s of the co n tro l t r e e s .
On the b a s is of the su gg estion by M u rn eek (70) that apple b lo s s o m s
of the f i r s t heavy drop m ay be divided into unpollinated flo w e rs and po llin ated
flo w e rs w h e re syng am y h as failed, the p i s t il s of the p e a c h flo w e rs which
d ro p p ed fro m the c o n tro l and NPA tr e a t e d t r e e s d u rin g the f i r s t heavy drop
w e r e e x a m in e d fo r grow th and developm ent.

A h ig her p o rtio n of the a b s c i s s e d

flo w e rs fro m the NPA t r e a t e d t r e e s contained a " d e v e lo p e d ” p is til than
th o se flo w e rs which dro pp ed fro m the c o n tro l t r e e s .

On the b a s is of th is

finding and a s s u m i n g that po llin atio n had s tim u la te d p is til developm ent ( 7 7 ),
the i n c r e a s e drop fro m the NPA t r e a t e d t r e e s o v e r the c o n tro ls a p p a re n tly
was due to a h e a v i e r drop of p o llin ated flo w ers.
M ic r o s c o p ic s tu d ie s of a b s c i s s e d flow ers with a ’'dev elop ed ” p is til
fro m the NPA t r e a t e d t r e e s r e v e a le d no evidence that f e rtiliz a tio n had taken
p la c e .

Thus, it a p p e a r s that NPA m ay hinder, in som e m an n er, the a c t of

sy n g am y e i t h e r in d ire c tly o r d ire c tly , and subsequently cau sin g a b s c is s io n
of the flo w er.

NPA evidently does not in te r f e r e with the pollination, a s s u m ­

ing th at the high n u m b e r of a b s c i s s e d flo w ers with ’’developed” p i s t i l s in d i­
ca te po llin atio n .
T r e a t m e n t s of NAA at 30 ppm m ade on June 7 and on June 14, 1958
r e s u l t e d in a sig n ifican t re d u c tio n of fru it set on Redhaven p each t r e e s (Table
3).

H ow ever, a t r e a tm e n t of NAA at the sam e c o n cen tratio n m ade on June

21 did not r e s u l t in any sig n ifican t f ru it red u ctio n (Table 3).

T h is would

in d icate th at the R edhaven v a r i e t y w as se n sitiv e to NAA u se d at 30 ppm fo r
thinning p u r p o s e s 35 and 42 days a f t e r bloom, but not 49 days.

F o r the

t r e a t m e n t s of NAA w hich r e d u c e d f ru it set sign ificantly th is would be seven
and 14 days a f t e r " s h u c k - o f f ” , a m e a n s of tim in g u se d by K elley (44) in Illinoi
H ib b ard and M u rn eek (33) found the m o s t fav o rab le tim e to thin the

E l b e r t a p e a c h w ith NAA w as 34 days a f t e r bloom, but Kelley (44) found the
m o s t f a v o ra b le tim e to th is th is v a r ie ty with NAA w as 38 days a f te r bloom
one y e a r an d 48 days a f t e r bloom a n o th e r y e a r.

However, it is in t e r e s t in g

th at in e a c h c a s e the effective ap p licatio n s of NAA o c c u r r e d a p p ro x im a te ly
14 days a f t e r " s h u c k -o ff" .

T h e s e in v e s tig a to rs found no sign ifican t thinning

when NAA w as ap p lied at "sh u ck -o ff", 21 days and 28 days a f t e r "shu ck-o ff",
but th in nin g o c c u r r e d when the tr e a tm e n t w as m ade seven and 14 days a f te r
" s h u c k -o ff" .

F r o m th e s e e x p e r ie n c e s it a p p e a r s that tim in g the a p p lic a tio n s

of NAA r e s u l t i n g in effective thinning could be b ased m o r e ad vantageo usly on
days a f t e r " sh u c k -o ff" r a t h e r than days a f te r bloom.
R e la tin g the tim e of NAA app licatio n with "June" drop, Kelley (44)
o b s e r v e d th a t ap p lic a tio n s of NAA m ade d u rin g o r a f te r "June" drop, 21 to
28 days a f t e r " sh u c k -o ff" , w e r e not effective in thinning p e a c h t r e e s .

T h e se

o b s e rv a tio n s c o r r o b o r a t e the findings of this study as the NAA applicatio n
m ade on R edhaven p each t r e e s June 21, 1958 at the beginning of the second
p e r io d of " Ju n e” drop did not r e s u l t in significant thinning.

However, the

two e a r l i e r t r e a t m e n ts m ad e on June 7 and on June 14 gave sig nificant th in ­
ning (T able 3, and F ig u r e 4).

The two tr e a t m e n ts of June 7 and June 14 w e re

m ad e d u rin g the f i r s t p e r io d of "June" drop o c c u r r in g June 7 to June 21.

F ro m

the r e s u l t s of th is study it would seem that K e lle y ’s (44) r e f e r e n c e to "June"
drop would co nfo rm to the seco nd p e rio d of "June" drop shown in F ig u re 4.
T h is seco n d p e r i o d of "June" drop w as typified by a h e a v ie r daily f ru it drop
than th e f i r s t p e rio d .

84.

T he NAA a p p lic a tio n on R edhaven t r e e s June 14 a p p e a re d to delay
the seco nd p e r i o d of "June" drop th r e e o r four days (F ig u re 4).

N e v e rth e le ss ,

th is p e r io d w as not extended o v e r any longer tim e by the NAA a p p licatio n s
c o n t r a r y to the findings of K elley (44) for the E lb e r ta p e a c h and of T e u b n e r
and M u rn e e k (96) fo r the Jonathan apple.

T he delay in fru it a b s c is s io n by

the u s e of NAA on the R edhaven p e a c h t r e e s a s found in this study m ay p e r h a p s
be ex p lain ed by the t e m p o r a r y p o s itiv e effect of the NAA on the a b s c is s io n
zone of the f ru it a s d e s c r ib e d by M u rn eek and T e u b n er (76) for the p e d ic e ls
of a p p le s when NAA is u sed fo r thinning.
An a tte m p t w as m ad e to r e l a t e the th re e s ta g e s of developm ent of
the p e a c h f r u i t s a s r e p o r t e d by Tukey (98) with the effe c tiv e n e s s of NAA
t r e a t m e n t s in thinning.

T he two t r e a t m e n ts of NAA on the Redhaven v a r ie ty

in 1958, w hich sig n ifican tly thinned the f ru its , w e re m ade d u rin g Stage I, the
tim e of r a p i d i n c r e a s e in s iz e of the p e r i c a r p when the developm ent of the
em b ry o w as in an " a r r e s t e d " s ta te (F ig u re 7).

The late NAA t r e a tm e n t

w hich did not sig n ifican tly re d u c e f ru it set, was m ade at the beginning of Stage
II, June 21, when the r a t e of e m b ry o grow th was ra p id and the r a te of g row th
of the p e r i c a r p had d eclin ed (F ig u re 7).

Thus, it would a p p e a r that a f te r the

e m b ry o e n t e r s the p e rio d of r a p id grow th stage, thinning can no lo ng er be
a c c o m p lis h e d b e c a u s e of the in c r e a s in g r e s i s t a n c e of the em b ry o to abo rtio n.
R ie ts e m a , S atina and B lakeslee (82) found evidence a lso that young D atura

e m b r y o s a r e m o r e s e n sitiv e to the effects of in do leacetic acid than advanced
em bryos.
A s s u m in g th a t e m b ry o a b o rtio n is involved in the thinning m ech an ism
of NAA, it a p p e a r s th at the em b ry o is s u sc e p tib le to NAA a p p licatio n s when
it is in the filam en to u s and the s p h e ric a l s ta g e s and that it is r e s i s t a n t in
th e tr a n s it i o n a l and l a t e r s ta g e s (T ab les 3 and 10).

T e u b n e r and M u rneek (96)

b e lie v e d th a t the ap p le e m b ry o was m o st su scep tib le in the 8 - to 1 6 -c e lle d
sta g e w hich would p la c e it in the filam en to u s stage, as c la s s if ie d by M ey er (67).
It is doubtful th at the use of NAA on p e a c h e s at the n o n -in ju rio u s r a t e of 30
ppm b e fo re June 7, one w eek a f te r ” shuck-off", would effectively re d u c e the
f r u it set, sin ce H ib b ard and M u rn eek (33) and Kelley (44) found that an a p p li­
catio n a t "sh u c k -o ff" o r e a r l i e r w as not effective.

The Redhaven p each e m b ry o s

w e r e about 4 6 - c e lle d one w eek a f te r "sh uck-o ff" and, th e r e fo r e , w e r e m o re
adv anced than the 8 - to 1 6 -c e lle d e m b ry o s of the apple (Table 8 ).

E m b ry o s

of the H alehaven v a r ie ty w e r e s i m i l a r to Redhaven in developm ent throughout
1957 and 1958 (T a b le s 6 and 7).

It m ay be c o n je c tu re d from th is that the p e a c h

e m b ry o is not as s e n s itiv e to NAA d u ring the e a r ly p a r t of the filam en to u s
stag e a s the apple e m b ry o .

However, fa ilu re of NAA to re d u c e the f ru it set

when the e m b r y o s a r e in the e a r l y p a r t of the filam en tou s stage m ay be a t t r i ­
buted to the lim ite d le a f s u rfa c e on the peach t r e e s d u rin g th is e a r l y stage,
r e s u l t i n g in r e d u c e d a b s o rp tio n of the thinning agent.

86.

It is b eliev ed that a c lo se study of the e a r ly developm ent of the
p e a c h e m b ry o would c o n trib u te to the su b jec t of fru it thinning by NAA.

The

type of e m b ry o found in the H alehaven and the Redhaven p each a p p e a re d to
be s i m i l a r to th a t of the Geum urbanum which was c la s s if ie d by Johansen (39)
a s the A s t e r a d type.

T h is type is typified by a single t r a n s v e r s e division in

the zygote w hich is followed by an oblique division in the t e r m in a l cell and
a seco n d t r a n s v e r s e d iv isio n in the b a s a l cell.

T e u b n e r and M u rn eek (96)

o b s e r v e d the sa m e type of develo pm en t in apple e m b ry o s of the Jonathan
v a r ie ty .

A p parently , the em b ry o type fo r the apple d iffers with the v a r ie ty

a s M e y e r (67) r e p o r t e d an em b ry o developm ent s im i l a r to the Solanad type
fo r M cIntosh.
T h e p r i m a r y d iffe re n c e in the e a r ly em b ry o developm ent between
the ap p le and the p e a c h a p p e a r s to be the length of tim e the em b ry o r e m a in s
in the fila m e n to u s sta g e .

T he p e a c h em b ry o as found in this study r e m a in e d

in the fila m e n to u s sta g e 28 days (T ab les 8 , 9 and 10) a s c o m p a re d to 10 days
fo r the apple e m b ry o r e p o r t e d by M e y e r (67).

The length of tim e in which

the p e a c h e m b ry o r e m a in e d in the s p h e ric a l and tra n s itio n a l stag e (T ables 8 ,
9 and 10) w as about the s a m e a s found in the apple by M ey er (67).

T h e re f o re ,

the s o - c a l l e d " a r r e s t e d " stag e com po sed of the filam en to u s and s p h e ric a l
s ta g e s of the p e a c h e m b ry o would be about two o r th re e w eeks lo n g er than
th a t of the apple w ith the lo n g er tim e of the filam ento us stage c r e a tin g the
d iffe re n c e .

T h e length of tim e of the " a r r e s t e d " stage of the p each a p p e a r s to
coin cid e c lo s e ly with th at of the p e a r (6 8 ).

M itchell (6 8 ) o b s e rv e d that e m b ry o s

of the B a rtle tt p e a r r e m a in e d m ic r o s c o p ic fo r eight w eeks a f t e r bloom a f te r
w hich tim e they in c r e a s e d in length ra p id ly .

T his c o m p a r e s to about eight

w eek s a f t e r bloom fo r the p e a c h em b ry o a s o b s e rv e d in th is study.
Luckw ill (62) found that the g r e a t e s t thinning effect obtained from NAA
on the C ra w le y Beauty v a r ie ty of apple w as d u rin g c e llu la r fo rm a tio n of the
e n d o s p e rm .

Based on L u c k w ill's r e p o rt, the thinning action of NAA on p each

t r e e s w as stu d ied to d e te r m in e if it w as r e la te d to en d o sp erm developm ent.
T he two NAA t r e a t m e n t s m ade in 1958 on Redhaven p each es, which r e s u lte d
in sig n ifican t thinning, w e r e app lied about th r e e days and 11 days b efore
c e l l u l a r f o rm a tio n of the e n d o sp e rm (F ig u re 7).

W h ereas, the NAA tr e a tm e n t

w hich did not r e s u l t in sig nificant thinning of Redhaven p e a c h e s w as m ade th r e e
d ays a f t e r c e l l u l a r fo rm a tio n ( F ig u re 7).

The NAA a p p licatio n s 42 days a f te r

bloom on H alehav en p each t r e e s in 1957 and 1958 w e r e ju st b efo re c e llu la r
f o rm a tio n of the e n d o s p e rm and a ls o r e s u lte d in sig nificant thinning (Table 3).
T h e r e f o r e , it a p p e a r s th at the ap p licatio n m ade when the e n d o sp erm is in the
f r e e - n u c l e a r s ta te ju st b e fo re c e l l u l a r developm ent, m ay be vital fo r the
thin n in g a c tio n of NAA.
O b s e rv a tio n s from this study indicate that c e llu la r fo rm atio n of the
e n d o s p e rm o c c u r r e d about two w eek s a f t e r "sh u c k -o ff .

A s su m in g that the

tim e of " sh u ck -o ff" r e f l e c t s s e e d and fru it developm ent m o re so than the

tim e of full bloom, it b e c o m e s evident that the NAA t r e a t m e n ts m ade by
H ib b a rd and M u rn e e k (33) and K elley (44) which gave effective thinning m u st
have b een ap p lied ju s t b efo re c e llu la r fo rm a tio n in the en d o sp erm .
It would be difficult to s ta te that the thinning action of NAA is m o re
dependent on the develo pm en t of the e n d o sp erm than the developm ent of the
em b ry o , sin c e they a r e in s e p a ra b le .

But, it would be even m o re difficult to

b eliev e th at the thinning action of NAA on p e a c h e s is independent of the
s p e c t a c u la r c e ll u l a r change of the en d o sp erm .
If the tim e of " sh u ck -o ff" can be used for d e te rm in in g the tim e of
the c e l l u l a r f o rm a tio n of the p each en d o sp erm for the p u rp o se of applying a
thinn ing agent, a s NAA, it would seem that a m o re exact m ethod could be
u sed.

The p r o c e s s of "sh u ck -o ff" o c c u r s slowly o v e r a p e r io d of about a

week, the r a t e of which can be a l t e r e d e a s ily by ra in and wind.

L in e a r size

of the young fru it in c r e a s e d v e r y ra p id ly before and during the c e llu la r f o r ­
m atio n of the e n d o s p e rm , in c r e a s in g at the r a te of about two m i l l i m e t e r s for
e v e r y t h r e e days ( F ig u r e s 5, 6 and 7).

The s iz e of the fru it of the H alehaven

and R ed hav en p e a c h w as a p p ro x im a te ly 30 m illim e te r s , o r one and th r e e s ix te e n th in ch es d u rin g the e n d o sp erm change ( F ig u re s 5, 6 and 7).

The tim e

of NAA a p p lic a tio n fo r effectiv e thinning could be d e te rm in e d p o s sib ly by
m e a s u r i n g the l in e a r siz e of p e r i c a r p at th r e e - o r f o u r-d a y in te rv a ls beginning
about one w eek a f te r " sh u c k -o ff" .

When the lin e a r dim en sio n of the fru it

89.

r e a c h e s about 29 m i l l i m e t e r s , o r one and o n e-eig h th inches, a NAA ap plication
at th is tim e and at the rig h t co n cen tratio n should give effective thinning.
F r o m the su g g estio n by Luckw ill (57, 59) that the accu m u latio n of
n a tu r a l h o rm o n e in the apple e n d o sp e rm could co ntro l a b s c is s io n of the young
fru it, a study w as m ade in 1958 to r e l a te the n a tu ra l h o rm o n e content and
c o n c e n tr a tio n in R edhaven p e a c h s e e d s with the n a tu ra l "June” drop.

It w as

found fro m th is study th at the n a tu r a l horm on e content of the p each s eed s w as
g r e a t e s t on June 15, which w as d u rin g the f ir s t p e rio d of "June" drop, about
one w eek b efo re the seco nd p e r io d of "June" drop ( F ig u re s 4 and 17).

In

c o n tr a s t, Luckw ill (59) found a low accu m u latio n of h orm o ne in apple s eed s
d u rin g "June" drop.
T h e c o n c e n tra tio n of the n a tu ra l h orm on e in the n e u tra l fra c tio n of
the p e a c h s e e d e x t r a c t s w as lo w er d u rin g the second p e rio d of "June" drop
than at the o th e r s a m p lin g d ates (F ig u r e s 4 and 16).

Even the c o n c e n tra tio n

of th is h o rm o n e did not a p p e a r to be r e l a t e d to n a tu ra l fru it drop.
Since the e n d o s p e rm of the p each seeds did not a p p e a r to be any l a r g e r
than the n u c e llu s d u rin g the sa m p lin g perio d , m o st of the n a tu ra l h orm on e
b io lo g ically a s s y e d could have com e fro m the nucellu s.

Luckwill (57, 58) w as

w o rk in g w ith apple s e e d s in which the e n d o sp erm m ad e up m o st of the volum e.
But sin c e the g r e a t e s t n a tu r a l h orm on e content w as found at the tim e of c e l lu l a r
f o rm a tio n of the p e a c h en d o s p e rm , it would seem that the l a r g e s t p o rtio n of the
h o rm o n e w as s e a te d in o r n e a r the em b ry o sac.

90.

The n a tu r a l h o rm o n e a ccu m u latio n in p each s e e d s d e c r e a s e d as the
r a t e of g ro w th of the e n d o sp e rm and e m b ry o i n c r e a s e d from June 21 to June
28, 1958 ( F ig u r e s 7, 16 and 17).

A fte r finding the s a m e r e la tio n s h ip betw een

the h o rm o n e content and e m b ry o gro w th in apple seeds, Luckw ill (57) s u g ­
g e s te d th at the h o rm o n e p la y s a p a r t in em b ry o developm ent d u rin g the p e r io d
of its ra p id grow th.

T e u b n e r and M u rn e e k (96) found th at the a c tiv ity of the

in d o le a c e tic a c id o x id a se s y ste m of apple e m b ry o s w as g r e a t e s t in the ra p id ly
dev elo pin g e m b r y o s .

The a c tiv ity of th is s y ste m m ay explain p a r t ia ll y the

d e c r e a s e of h o rm o n e a c c u m u la tio n d u rin g the i n c r e a s e d grow th of the em bryo ,
a s s u m i n g th at the h o rm o n e s w hich w e r e is o la te d could be oxidized by the s a m e
s y s te m .
It is difficult to r e l a t e the thinning e ffe c tiv e n e s s of NAA on peach
t r e e s w ith n a tu ra l h o rm o n e a c c u m u la tio n in the p e a c h s e e d s.

The two t r e a t ­

m e n ts of NAA on R edhaven p e a c h t r e e s th at r e s u l te d in sig n ifican t thinning
w e r e m a d e one day and eight days b e fo re the tim e of the g r e a t e s t n a tu r a l h o r ­
m one content in the p e a c h s e e d (T able 3, and F ig u re 17).

The NAA a p p l i c a ­

tion m ade six days a f t e r the tim e of the g r e a t e s t h o rm o n e content r e s u l t e d in
no sig n ifican t thin nin g of p e a c h t r e e s (T able 3 and F ig u r e 17).

It is p o s s ib le

th a t the ad d itio n of an exogenous supply of NAA to the se e d would r e s u l t in
the in h ib itio n of the e m b ry o th ro u g h c o m p etitio n w ith the n a tu r a l h o rm o n e of
a high content, a s T e u b n e r and M u rn e e k (96) su g g ested in th in nin g a p p le s.

91.

M o re w o rk is n e c e s s a r y to s u b sta n tia te o r d isp ro v e th is suggestion.
Of the two a p p a re n t h o rm o n e s e x tr a c te d from the Redhaven p each
s e e d s, t h e r e is a s tr o n g in d icatio n that one of the n a tu r a l h o rm o n e s w as ethyl
in d o le a c e ta te .

T h e r e is no p o s itiv e evidence that the o th e r h o rm o n e w as a

indole d e r iv a tiv e compound.

T e u b n e r (94) identified ethyl in d o le a c e ta te a s

the n a t u r a l h o rm o n e p r e s e n t in apple s e e d s.

Of th re e n a tu r a l h o rm o n e s

i s o la te d fro m se e d s, f ru its , and le a v e s of apples, Luckw ill (63) found one
h o rm o n e w ith p r o p e r t i e s s i m i l a r to ethyl in d o leacetate.
m o n e s did not a p p e a r to be indole d e riv a tiv e com pounds.

The o th e r two h o r ­
The two unidentified

n a tu r a l h o rm o n e s w e r e found to be p r e s e n t in apple s e e d s only b efo re and
d u rin g the tim e of c e l l u l a r fo rm a tio n of the e n d o s p e rm .

The indole d e r i v a ­

tiv e h o rm o n e w as p r e s e n t before, d u rin g and a f t e r the tim e of the e n d o s p e rm
change fro m f r e e - n u c l e a r to c e l l u l a r fo rm .
A n a tu r a l in h ib ito r to the grow th of coleop tile s e c tio n s of o a ts was
found in the n e u tr a l fra c tio n of the June 15 e x t r a c t from p e a c h se e d s (T able 14
and F i g u r e 19).

T h e in h ib ito r w as lo c a te d on c h r o m a to g r a m s at Rf 0. 1 to 0. 2,

u s in g a 2 -p ro p a n o l, am m o n ia, w a te r solvent of a 8:1:1 volum e r a tio .
not p o s s ib le to identify it.

It w as

Luckw ill (63) iso la te d two in h ib ito rs fro m apple

s e e d s of which one w as p r e s e n t only b efo re and the o th e r p r e s e n t only a f t e r
c e l l u l a r fo rm a tio n of the e n d o s p e rm .

He could not p o s itiv e ly identify them .

T h e r e s u l t s of t h e s e stu d ie s in d ic a te quite d efinitely th at two plant

92.

r e g u l a t o r s , NPA and NAA, a r e p r o m i s i n g b lo sso m and f r u it thinning a g e n ts of
peach tre e s.

The u se of NPA h a s the advantage of d e c r e a s in g b lo sso m se t

e a r l y in the seaso n , for in c r e a s e d fru it size, and for an in c r e a s e d n u m b er of
flo w e r buds the follow ing s p rin g .

At the p r e s e n t tim e NAA a p p e a r s to be the

m o r e fa v o ra b le of the two a s a thinning agent b ecau se of the p o s s ib ility of
thin n in g a f t e r the d a n g e r of s p rin g fro s t.

93.

SUMMARY

1.

A s e r i e s of s tu d ie s w e r e conducted d u rin g the p e r io d of 1955

th ro u g h 1958 to d e te r m in e the tim e of application, and the value of naphthalene a c e tic a c id (NAA), N -1 -n a p h th y lp h th a la m ic a c id (NPA), and 3 - c h lo r o - is o p r o p y lN -p h en y l c a r b a m a te (3 -c h lo ro IPC) fo r b lo sso m and fru it thinning of p e a c h e s .
a. R edhaven t r e e s w e r e o v e r thinned by NPA at 300 ppm
a p p lie d t h r e e days a f t e r full bloom in 1956 and 1958.

T r e e s t r e a t e d w ith NPA

a t 200 an d 400 ppm in 1955; with NPA at 200, 250 and 300 ppm in 1957; and
w ith NPA a t 250 ppm in 1958, had to be h and-thinned.

In 1956, H alehaven

t r e e s w e r e thinned effectiv ely w ith 300 ppm NPA ap p lied th r e e days a f te r full
bloom .

H aleh av en t r e e s t r e a t e d with NPA at 200 and 400 ppm in 1955; w ith

NPA at 200, 250 and 300 ppm in 1957; and w ith NPA at 250 and 300 ppm in
1958, r e q u i r e d hand -th in n in g .
b. The u s e of 3 - c h lo ro IPC at 400 ppm on Redhaven and H a le ­
hav en fo u r w eeks a f t e r bloom in 1956 and 1957 did not thin su fficien tly to e l i m ­
inate h an d -th in n in g .

It's us e did h a s te n rip e n in g of the f r u it a s m e a s u r e d by

f i r m n e s s of flesh, and did r e s u l t in u n d e s ira b le "beak ed" p e a c h e s (F ig u re 1).
B ecause of the u n d e s ir a b le sh ap e of the p e a c h e s r e s u l t i n g from i t ’s use, 3ch lo ro IPC w as e lim in a te d fro m f u r t h e r testin g .
c. NAA at 300 ppm ap p lied 42 days a f t e r bloom, two w eeks
a f t e r " s h u c k - o f f ” , in 1957 and 1958, gave sig nificant f r u it thinning on Redhaven

94.

and H aleh av en t r e e s .

An ap p licatio n of NAA on Redhaven t r e e s 35 days a f te r

bloom , one w eek a f t e r ” shu ck -o ff", at 30 ppm r e s u lt e d in sig nifican t thinning
in 1958; but a n a p p lic a tio n of NAA 49 days a f te r bloom r e s u l t e d in no a p p a re n t
thinning.
d. T he s iz e of R edhaven and H alehaven p e a c h e s w as in c r e a s e d
in 1956 by the u s e of NPA at 300 ppm .

However, the u se of 3 - c h lo ro IPC at

400 ppm i n c r e a s e d the s iz e of the fru it of only the Redhaven v a rie ty .
e. An a p p lic a tio n of NAA at 30 ppm 42 days a f te r bloom on
R ed hav en and H alehaven t r e e s in 1957 sig n ifican tly re d u c e d the n u m b e r of
flo w e r buds in the s p r in g of 1958.

T h e r e w as a sig n ifican t in c r e a s e in the

n u m b e r of flo w e r buds on Redhaven t r e e s tr e a t e d with NPA at 300 ppm th r e e
days a f t e r bloom in 1957 when c o m p a re d to th ose t r e e s r e c e iv in g no t r e a t ­
m en t.
2.

In o r d e r to ev a lu a te the p a t te r n of fru it drop, a study w as in itia te d

in 1958 to c o m p a r e the n a tu r a l drop of b lo s s o m s and young f r u its fro m Redhaven
p e a c h t r e e s w ith the drop r e s u lt i n g fro m the use of NAA and NPA a s thinning
a g e n ts.
a.

The daily b lo ss o m drop of the c o n tro l t r e e s w as h e a v ie s t

d u rin g a p e r io d of s e v e n days a f t e r bloom .

M ost of the drop fro m the R edhaven

p e a c h t r e e s , w hich r e c e iv e d an a p p lic a tio n of NPA at 300 ppm th r e e days a f t e r
bloom took p la c e d u rin g th is sa m e p e rio d .

S ixty-five p e r c e n t of the b lo s s o m s

95.

w hich d ro p p ed se v e n days a f t e r bloom from the NPA t r e a t e d t r e e s w e r e p o llin ­
ated, w h e r e a s only a p p ro x im a te ly 2 0 p e r c e n t of the b lo s s o m s w hich dropped
f ro m the c o n tro l t r e e s w e r e p o llin ated .

T h e r e w as no in dicatio n that syn gam y

had ta k e n p la c e in the p o llin a te d p is ti l s of the a b s c i s s e d flo w ers.
b.

The s o - c a l le d "June'' drop of the c o n tro l t r e e s w as divided

into a f i r s t and secon d p e r io d of heavy fru it drop.

The f i r s t p e rio d of heavy

f r u it drop o c c u r r e d a p p ro x im a te ly 35 days a f t e r bloom and re m a in e d c o n sta n t
fo r 14 days.

T he second p e r io d of drop o c c u r r e d about 49 days a f t e r bloom

and la s t e d fo r 11 day s.

An a p p licatio n of NAA at 30 ppm 42 days a f te r bloom

a p p e a r e d to d elay the second p e r io d of "June" drop by th r e e days, but it did
not ex ten d th is p e r io d fo r any lo n g e r tim e .
3.

A n a to m ic a l in v e stig a tio n s w e r e m ade in 1957 and 1958 on H alehaven

and R edh aven p e a c h e s so a s to r e l a t e the developm ent of the em b ryo , en d o ­
s p e rm , and p e r i c a r p w ith the tim e of a p p licatio n of the p lant r e g u la to r s , NPA
and NAA, fo r m o r e effectiv e thinning.
a.

M ic r o s c o p ic e x a m in a tio n s of the R edhaven p e a c h re v e a le d

th at sy ng am y took p la c e b etw een sev en and 14 days a f t e r bloom in 1958.

The

p e a c h e m b r y o of both the H aleh av en and Redhaven v a r i e t i e s g rew v e r y slowly
in length, width and c e ll n u m b e r fo r about 35 days a f t e r syngam y d u rin g the
s o - c a l l e d " a r r e s t e d " stag e .

The e m b ry o continued in the filam en to u s stage,

l i n e a r in shape, fo r a 2 8 -d ay p e rio d , a fo rm which developed im m e d ia te ly

96.

a f t e r the f i r s t d iv isio n of the zygote, 14 days a f te r bloom .

The em b ry o becam e

bulbous in shape, the s p h e r ic a l stage, a p p ro x im a te ly 42 days a f t e r bloom which
continued fo r sev en to ten days.

R apid grow th of p e a c h e m b ry o w as o b s e rv e d

about 49 days a f t e r bloom d u rin g the tr a n s itio n a l stage, when the e m b ry o
ch an g ed to a tr ia n g le shape.

The ra p id r a te continued throughout the e a r l y

c o ty le d o n a ry stag e w hich followed seven days la te r .
b. The e n d o s p e rm of the p e a c h continued in a f r e e - n u c l e a r
s ta te fo r a p p r o x im a te ly 32 days a f t e r syngam y and changed to a c e llu la r c o n ­
ditio n about 42 days a f t e r full bloom, two w eeks a f te r " s h u c k - o f f 1.

The en d o ­

s p e r m g re w ra p id ly in width and length a p p ro x im a te ly sev en days a f t e r c e l l u l a r
fo rm a tio n .
c. The seed and p e r i c a r p of the p e a c h continued to grow at
a r a p id r a t e fo r a p e r io d of 49 days a f t e r bloom when a s h a rp decline o c c u r re d .
The e n d o c a rp of the p e a c h began to h a r d e n about 35 days a f te r bloom .

"Shuck-

off" w as found to o c c u r a p p ro x im a te ly 30 days a f t e r full bloom in 1957 and 1958
fo r both th e R edh aven and H aleh av en v a r i e tie s .
4.

F r u i t c o lle c tio n s fro m Redhaven t r e e s w e r e m ade June 2, 1958,

fo u r w eek s a f t e r bloom , and at w eekly in te rv a ls t h e r e a f t e r fo r a p e r io d of
fo u r w eek s in o r d e r to d e te r m in e the r e la tiv e c o n c e n tra tio n and content of
n a t u r a l h o r m o n e s o c c u r r i n g in p e a c h s e e d s.
a. The n a tu r a l h o rm o n e content of both a c id and n e u tra l f r a c tio n s

97.

fro m p e a c h s e e d e x t r a c t s r e a c h e d a m ax im u m in quantity on June 15, six w eeks
a f t e r bloom .

T he c o n c e n tra tio n of the n a tu ra l ho rm o n e in the s e e d s w as h ig h est

on June 15 fo r the acid f ra c tio n of the e x tr a c t.

The h o rm o n e c o n c e n tra tio n of

the n e u tr a l f r a c tio n w as r e la tiv e ly the sa m e for the f i r s t th re e d ates of sam pling,
June 2, 7 and 15, a f t e r which tim e it d e c r e a s e d m a rk e d ly .
b.

C h ro m a to g ra p h p a p e r s w e r e spotted with the acid and n e u tr

f r a c t io n s of e x t r a c t s fro m p e a c h s e e d s and w e r e m i g r a te d with a 8 : 1:1 volum e
r a t io so lv en t of 2 -p ro p an o l, am m o nia, and w a te r.

F ro m v a rio u s q u alitativ e

t e s t s , it a p p e a r e d th a t the n e u tr a l h o rm o n e p r e s e n t in the acid f ra c tio n of the
e x tr a c tio n fro m the R edhaven p e a c h s e e d s was not IAA.

T h e r e w as a s tr o n g

in dication, how ever, that the n a tu ra l ho rm o n e p r e s e n t in the n e u tra l fra c tio n
of the e x tr a c tio n w as EtIA.
The r e s u l t s of th e s e s tu d ie s ind icate quite definitely that two p lan t
r e g u l a t o r s , NPA and NAA, a r e p r o m is in g blosso m and f ru it thinning agen ts
of p e a c h t r e e s .

Of th e s e two, NAA a p p e a r s to be m o r e fav o rab le a s a thinning

agen t b e c a u s e of the p o s s ib ility of thinning a f te r the d an g er of s p r in g fro s t.

98.

LITERA TU R E CITED
1. A ld e rm a n , D e fo re s t. 1955. A lp h a-n ap h th y lacetam id e: A c h e m ic a l f r u it
th in n e r. P ro c. A m e r. Soc. H ort. Sci. 6 6 : 57-64.
2. A m e r ic a n C h em ical Paint Company.
S e rv ic e D ata Sheet H-71.
3.

1958.

A u ch ter, E. C. , and J. W . R o b e rts . 1933.
a p p le s fo r the p r e v e n tio n of fru it set.
Sci. 30: 22-25.

ACP P e a c h -T h in 322.

Techn.

E x p e rim e n ts in s p ra y in g
P roc. A m er. Soc. H ort.

4. ____________________________________ . 1934. S p ray in g ap p les fo r the
p r e v e n tio n of f r u it set. P ro c . A m e r. Soc. H ort. Sci. 32: 208-212.
5. Baker, G. A . , and L. D. D avis. 1951. G row th of the cheek d ia m e te r
of p e a c h e s . P ro c. A m er. Soc. H ort. Sci. 57: 104-110.
6.

B atjer, L. P.
sprays.

, and M. B. Hoffman. 1951. F r u it thinning with c h e m ic a l
U. S. Dept. A gr. C irc . No. 867.

7. Bradbury, D orothy. 1929. A c o m p a ra tiv e study of the developing and
a b o r tin g f r u i ts of P ru n u s c e r a s u s . A m er. Jour. Bot. 16: 525-542.
8 . Brink, R. A. , and D. C. C ooper.

M edicago Sativa.

1939. S o m ato p lastic s te r i li t y in
Science 90: 545-546.

. 1940.
9. ________________________________
m e n t of the s e e d in A n g io s p e rm s .
10.
m en t.

• 1947.
Bot. Rev. 13: 423-541.

Double f e rtiliz a tio n and d e v e lo p ­
Bot. Gaz. 102: 1-25.
The e n d o sp e rm in se e d d ev e lo p ­

11. Britten, E. J. 1947. The effect of n ap h th a le n e a c e tic acid on the developing
m a iz e c o r y o p s is . A m e r. Jour. Bot. 34: 211-218.
12. Brooks, R eid M. 1939. A grow th study of the alm on d fru it.
Soc. H ort. Sci. 37: 193-197.
13.

P ro c . A m e r.

Bryant, L. R. 1935. A study of the f a c to r s a ffectin g the developm ent of the
em b ry o in the M cIntosh apple. Univ. New Hamp. Agr. Exp. Sta.
Tech. Bui. 61.

99.

14. B urkholder, C. L. , and W. D. A r m s tr o n g . 1956.
in 1956. P urd ue Univ. M im eo HO 51-1.

P each thinning t r i a l s

15. ___________________ , and M. McCown. 1941. E ffe c ts of s c o rin g and of a naphthyl a c e tic a c id and am id e s p ra y upon fru it set and of the s p ra y
upon p r e - h a r v e s t fru it drop. P roc. A m e r. Soc. H ort. Sci. 38: 1171 20 .
16. C onnors, C. H. 1919. G row th of f r u its of p each.
Sta. Ann. Rep. 40: 82-88.

New J e r s e y A gr. Exp.

17. Cooper, D. C . , and R. A. Brink. 1940. S o m ato p lastic s t e r i l i t y a s a
c a u s e of s e e d fa ilu r e a f t e r in te rs p e c if ic h y b rid izatio n . G en etics
25: 593-617.
18.

. 1940. P a r ti a l s e lf-in c o m p a tib ility and
the c o lla p se of f e r t i le ovules a ffectin g seed fo rm a tio n in alfalfa. Jour.
A g r. R es. 60: 453-472.

19.

. 1942. The e n d o sp e rm a s a b a r r i e r to
i n t e r s p e c if ic h y b rid iz a tio n in flo w erin g p la n ts. Science 95: 75-76.

20.

. 1944. C ollapse of the s e e d following
and m a tin g of H ordeum jubatum x S ecale c e r e a le . G e n e tic s 29: 370 390.

21.

, and H. R. A lb rech t. 1937. E m b ry o
m o r t a l i t y in r e la tio n to seed fo rm a tio n in alfalfa, (M edicago s a tiv a ).
A m e r . Jour. Bot. 24: 203-213.

22. D avidson, J. H. , O. H. H a m m e r, C. A. R e im e r and W. C. Dutton. 1945.
T h inning a p p le s w ith the sodium s a lt of naphthyl a c e tic acid. M ich.
A g r. Exp. Sta. Q uart. Bui. 27: No. 3.
23. D avidson, R. M. 1955. The u se of c h e m ic a l thinning s p r a y s on apple t r e e s
in New Z e a la n d . II. F u r t h e r e x p e r im e n ts with d initro com pounds and
s y n th e tic g row th s u b s ta n c e s . New Z e alan d Jour. Sci. and T ech. Sec.
A, Vol. 37, No. 1.
24.

. 1956. The u s e of c h em ical thinning s p r a y s on apple t r e e s
in New Z e a la n d . III. E ffect on f r u it s to ra g e life. New Z e a la n d Jour.
Sci. and T ech . Sec. A, Vol. 38, No. 1.

100.

25. D avison, R. M. 1956. The u se of c h e m ic a l thinning s p ra y s on apple t r e e s
in New Z e alan d . IV. C o m p atibility of grow th s u b s ta n c e s with t h e r a p e u ta n t s p r a y s . New Z e a la n d Jour. Sci. and T ech. Sec. A, Vol. 38,
No. 1.
26. D etjen, L. R. 1926. P h ysiolo gical dropp in g of f ru its . I. R elatio n of
po llin atio n , f e r tiliz a tio n and e m b ry o ab o rtio n to a b s c is s io n f ru its .
Del. A gr. Exp. Sta. Bui. 143.
of f ru its .
27. ______________, and G. F . G ray . 1928. P h ysiolo gical dropp in g
II. In r e g a r d to g en etic r e la tio n s h ip s of p la n ts. Del. A gr. Exp. Sta.
Bui. 157.
28. D o rse y , M. J. 1939. A study of the c a u s e s of ’'Buttons" in the J. H. Hale
p e a c h . 111. A gr. Exp. Sta. Bui. 458.
29. E d g e rto n , L. J. , and M. B. Hoffman. 1955. E ffect of N -l-n a p h th y lp h th a la m ic a c id on fru it set of p e a c h e s . Science 121: 467-468.
30. G a r d n e r , F. E . , P. C. M arth , and L. P. Batjer. 1939. S p ray in g with
p la n t gro w th s u b s ta n c e s fo r the co n tro l of p r e h a r v e s t drop of app les.
P ro c . A m e r. Soc. H ort. Sci. 37: 415-428.
31. G re e n e , L. 1943. G row th r e g u l a t o r s and fru it s e t with S ta rk in g ap ples.
P ro c . A m e r. Soc. H ort. Sci. 42: 149-150.
32. H a r ro ld , T. J. 1935. C o m p a ra tiv e study of the developing and a b o rtin g
f r u i t s of P ru n u s p e r s i c a . Bot. Gaz. 96: 505-520.
33. H ibbard, A. D. , and A. E. M urneek .
m one s p ra y s . P ro c. A m e r. Soc.
34. Hoffman, M. B.
48-51.
35.

1953.

1950. Thinning p e a c h e s with h o r ­
H ort. Sci. 56: 65-69.

S p ray ing ap p les.

A m e r.

F r.

G ro w e r 73 (2): 25,

, F. W. Southwick, and L. J. E d g e rto n . 1947. A c o m ­
p a r i s o n of two ty p es of m a t e r i a l fo r the c h e m ic a l thinning of app les.
P ro c . A m e r . Soc. H ort. Sci. 49: 37-41.

36. H o rsfa ll, F. J r . , and R. C. M oore. 1956. Iso p ro p y l N - (3 chlo rop hen yl)c a r b a m a t e s and o th e r c a r b a m a t e s a s fru it thinning s p ra y s for H a le ­
haven, A m b e rg e m and E l b e r t a p e a c h e s . P roc. Amer. Soc. Hort. Sci.
6 8 : 63-69.

37. Howlett, F. S. 1931. F a c t o r s affectin g fru it setting.
W inesap. Ohio A gr. Exp. Sta. Bui. 483.
38. Johansen, D. A. 1950.
W altham , M a ss .

P lant em bry olog y.

I. Staym an

C hro nica Botanica Co.

40. Kelley, V. W. 1952. R e s u lts of the 1952 c h e m ic a l p e a c h thinning
t e s t s . T r a n s . 111. H ort. Soc. 8 6 : 228-231.
41. ______________. 1953. U p -to -d a te in c h e m ic a l p each thinning.
111. H o rt. Soc. 87: 95-101.

T rans.

42. ______________. 1954. C h em ical thinning of ap p les and p e a c h e s . T r a n s .
111. H o rt. Soc. 8 8 : 211-219.
43. ______________. 1955. E ffect of c e r t a in thinning m a t e r i a l s on n u m b er
of f r u i t buds f o rm e d in E l b e r t a and H alehaven p e a c h e s . P roc.
A m e r. Soc. H ort. Sci. 6 6 : 67-69.
44.

. 1955. T im e of a p p licatio n of N ap h th alen eacetic acid
fo r fru it thinning of the p e a c h in r e la tio n to the June drop. P roc.
A m e r . Soc. H ort. Sci. 6 6 : 70-72.

45. Knight, L. I. 1917. P h y sio lo g ical a s p e c ts of s e l f - s t e r i l i t y of the
apple. P ro c. A m e r. Soc. H ort. Sci. 14: 101-105.
46. K ra u s, E. J. 1915.
549-557.

The s e l f - s t e r i l i t y p ro b le m .

Jour. H ered. 6 :

47. L illelan d , O. 1930. G row th study of the a p r ic o t fru it.
Soc. H ort. Sci. 27: 237-245.

P ro c. A m e r.

48.

. 1932. G ro w th study of the p each fru it.
H o rt. Sci. 29: 8-12.

49.

. 1933. G row th study of the plum fru it I. P roc.
H ort. Sci. 30: 203-208.

50.

. 1935. G row th study of the a p r ic o t fru it, II. The effect
of t e m p e r a t u r e . P ro c . A m e r. Soc. H ort. Sci. 33: 269-279.

51.
fru it.

P ro c. A m e r. Soc.

A m e r. Soc.

, and L. N ew som e. 1935. A grow th study of the c h e r r y
P ro c. A m e r. Soc. H o rt. Sci. 32: 291-299.

102.

52. Lott, R. V. 1933. The grow th r a te and c h e m ic a l co m p o sitio n of the
H iley p e a c h fro m stone fo rm a tio n to fle sh m a tu rity . P ro c. A m e r.
Soc. H o rt. Sci. 29: 1-7.
53.
Soc.
54.

. 1934. F u r t h e r s tu d ie s of p e a c h
H o rt. Sci. 30: 201-202.

fru it grow th.

P roc. A m e r.

, and T. E. A shley. 1935.
Some v a r i e t a l d iffe re n c e s in fru it
d ev elo pm en t in p e a c h e s . P ro c. A m e r. Soc. H ort. Sci. 3 3 :2 5 8 -2 6 4 .

55. Luckw ill, L. C. 1946.
N a tu re 158: 663.

A f r u i t - s e t t i n g h o rm o n e from apple s e e d s.

56.

. 1948. A m ethod fo r the quantitativ e e s tim a tio n of
g row th s u b s ta n c e s b a se d on the r e s p o n s e of tom ato o v a r ie s to known
a m o u n ts of 2 - nap th o x y -a c e tic acid. Jour. Hort. Sci. 24: 19-31.

57.

. 1948. T he h o rm o n e content of the seed in r e la tio n
to e n d o s p e rm d evelopm ent and f ru it drop in the apple. Jour. H ort.
Sci. 24: 32-44.

58.

. 1949. F r u i t developm ent in r e la tio n to plant h o rm o n e s.
E n d e a v o r 8 : 188-193.

59.
m en t.
60.
ag e n ts .
33-40.

. 1949. F r u i t drop in the apple in r e la tio n to seed d ev elo p ­
Ann. Appl. Biol. 36: 567-568.
. 1951. T r i a l s w ith grow th s u b s ta n c e s a s fru it-th in n in g
Ann. Rept. A gr. H ort. S ta ., Long Ashton, B ristol, 1 95 1 p p .

61.

. 1953. Studies of f ru it developm ent in r e la tio n to plan t
h o r m o n e s . I. H orm one P ro d u ctio n by the developing apple seed in r e l a ­
tion to f r u it drop. Jour. H o rt. Sci. 28: 14-24.

62.

. 1953. Studies of f r u it d evelopm ent in r e la tio n to plant
h o r m o n e s . II. The effect of naphthalene a c e tic a c id on f ru it set and
f r u it d ev elop m ent in a p p le s. Jour. H ort. Sci. 28: 25-40.

63.

. 1957. Studies of fru it developm ent in r e la tio n to p lan t
h o rm o n e s . IV. A cidic au x in s and grow th in h ib ito rs in le a v e s and fru it
of the apple. Jour. H ort. Sci. 32: 18-33.

103.

64. Luckw ill, L. C. , and D. Woodcock. 1950. A p r e l i m i n a r y in v estig atio n
into the n a tu r e of the h o rm o n e p ro d u c e d by developing apple se e d s.
Ann. Rept. A gr. H o rt. R es. S ta ., Long Ashton, B ristol, 1950. p. 23.
65. M a h e sh w a ri, P.
New Y ork.

1950.

E m b ry o lo g y of A n g io s p e rm s .

M cG raw -H ill,

6 6 . M a rth , P.

C. , and V. E. P rin c e . 1953. E ffect of 3 - c h lo r o - is o p r o p y l- N p henyl c a r b a m a t e on a b s c is s io n of young f r u its of peach. Science 117:
497-498.

67. M e y e r, C. F . 1958. Cell p a t t e r n s in e a r l y em b ry o g en y of the M cIntosh
ap ple. A m e r. Jour. Bot. 45: 341-349.
6 8 . M itchell, A. E.

1950. G r o s s m o rphology and histology of the developing
f r u it of the B artlett p e a r . P h .D . T h e s is , Ohio State U n iv e rsity .

69. M uir, R. M. 1942. G row th h o rm o n e s a s r e la t e d to se ttin g and developm ent
of f r u it of N icotian a ta b a c c u m . A m e r. Jour. Bot. 29: 716-720.
70. M u rn eek , A. E. 1932. G row th and developm ent a s influenced by fru it
and se e d fo rm a tio n . Plant Physiol. 7: 79-90.
71.

. 1933. The n a tu r e of shedding of im m a tu re a p p les.
A g r. Exp. Sta. R es. Bui. 201: 1-34.

72.
thinning.

Mo.

. 1950. T he r e l a t iv e value of h o rm o n e s p r a y s for apple
P ro c . A m e r . Soc. H o rt. Sci. 55: 127-136.

73.

. 1951. G r o w th -r e g u la tin g s u b sta n c e s in r e la tio n to r e ­
p ro d u c tio n of so m e h o r ti c u l tu r a l p lan ts. In F. Skoog. , Ed. Plant
G row th S u b sta n c e s. Univ. of W is. P r e s s , M adison, pp. 329-345.

74.

. 1952. P lant g r o w th - r e g u la to r s d u rin g f e r tiliz a tio n and
p o s t - f e r t i l i z a t i o n p e r i o d s . P roc. A m e r. Soc. H o rt. Sci. 59: 207-217.

75.

, and A. D. H ibbard. 1947. In v e stig atio n s on thinning
of p e a c h e s by m e a n s of c a u s tic and "h o rm o n e " s p ra y s . P ro c . A m er.
Soc. H o rt. Sci. 50: 206-208.

76.

, and F. G. T e u b n e r.
a c e tic a c id in th in n in g of a p p le s.
154.

1953. The dual actio n of naph th aleneP ro c. A m e r. Soc. H ort. Sci. 61: 149-

104.

77. N itsch, J. P. 1952. P lant h o rm o n e s in the d evelopm ent of f ru its .
Rev. Biol. 27: 33-57.

Q uar.

78. ____________ , and C. N itsch . 1954. G row th of coleop tile and f i r s t
in te rn o d e s e c tio n s . A new se n sitiv e , s tr a ig h t-g r o w th t e s t for
auxin. Plant P hysiol. 31: 94-111.
79. O s te r w a ld e r , A. 1910. Blutenbiologie, E m b ry o lo g ie und Entw icklung
d e r F r u c h t u n s e r e r K ern o b stb au m . Lands. Jahrb. 39: 917-998.
80. P ech o u tre, F. 1902. C o ntrib utio n a I ’etude de developm ent de l'o v u le
et de la g r a in e d es R o s a c e e s . A nnales. Sci. Nat. 16. S er. 8 : 1 158.
81. R edem ann, C. T. , S. H. W ittw er and H. M. Sell. 1951. The f r u its e ttin g f a c to r fro m the ethanol e x tr a c ts of i m m a tu r e c o rn k e r n e ls .
A rch . Biochem. and Biophys. 32: 80-84.
82. R ie ts e m a , J . , S. Satina and A. F. Blakeslee. 1953. The effect of indole3 - a c e tic a c id on D a tu ra e m b r y o s . P ro c. Natl. Acad. Sci. U. S. 39:
924-933.
83. Rood, P. 1957. D evelopm ent and evaluatio n of objectiv e m a tu r ity in dices
fo r C a lifo rn ia f re e s to n e p e a c h e s . P ro c. A m e r. Soc. H ort. Sci. 70:
104-112.
84. S ch n eid er, G. W ., and J. V. E nzie. 1943. T h e effect of c e r t a in c h e m i­
c a ls on the fru it se t of the apple. P ro c. A m e r. Soc. Hort. Sci. 42:
167-176.
85.

. 1944. F u r t h e r s tu d ie s on the effect
of c e r t a i n c h e m ic a ls on f r u i t set of the apple. P ro c. A m er. Soc. Hort.
Sci. 45: 6 3-68.

8 6 . Sen, S. P ., and A. C. Leopold.

1954. P a p e r c h ro m a to g ra p h y of plan t
g ro w th r e g u l a t o r s and a llie d com pounds. Physiol. P lan taru m 7:
98-108.

87. Southwick, F. W. , L. J. E d g e rto n and M. B. Hoffman. 1947. Studies
in thinning p e a c h e s w ith b lo sso m re m o v a l s p ra y s . P roc. A m e r.
Soc. H ort. Sci. 49: 26-32.

105.

8 8 . Southwick,

F. W . , M. B. Hoffman and L. J. E dg e rto n . 1948. F u r t h e r
e x p e r ie n c e s with c h e m ic a l thinning of ap p les and p e a c h e s . P ro c.
A m e r . Soc. H ort. Sci. 51; 41-47.

89. __________________ , and W. F . Weeks. 1949. C hem ical thinning of ap ples
at b lo ss o m tim e and up to four w eeks fro m p e ta l fall. P roc. A m e r .
Soc. H ort. Sci. 53: 143-147.
90.

_________________________________ . 1950. Some a tte m p ts to thin ap p les
w ith n a p h th a le n e a c e tic type m a t e r i a l s a f te r calyx. P ro c. A m er. Soc.
H o rt. Sci. 56: 70-75.

91. Stebbins, T. C. , A. L. Neal and V. R. G a rd n e r. 1946. Thinning ap p les
a t b lo sso m tim e w ith g row th re g u la tin g s u b s ta n c e s and o il-w a x e m u l­
sio n s. P ro c . A m e r. Soc. H ort. Sci. 48: 63-66.
92. Stowe, B. B. , and K. V. T him ann. 1954. The p a p e r c h ro m a to g ra p h y of
indole com pounds and so m e indole con taining auxins of p lan t tis s u e .
A rch . Biochem. and Biophys. 51: 499-516.
93. S tru c k m e y e r, B. E s t e r and R. H. R o b e r ts . 1950. A p o s s ib le explanation
of how n a p h th a le n e a c e tic a c id th ins ap p les. P ro c . A m e r. Soc. H ort.
Sci. 56: 76-78.
94. T e u b n e r, F. G. 1953. Id entification of the auxin p r e s e n t in apple e n d o ­
s p e r m . S cien ce 118: 418.
95.

. 1958. S e p a ra tio n of a c id ic and n onacidic h o rm o n e s and
av en a s tr a i g h t grow th t e s t. U npublished in form atio n.

96.

, and A. E. M u rn eek . 1955. E m b ry o a b o rtio n a s m e c h a n ­
ism of " h o rm o n e " thin nin g of fru it. Mo. A gr. Exp. Sta. R es. Bui.
590.

97. Tukey, H. B. 1933. E m b ry o a b o rtio n in e a r l y - r i p e n i n g v a r i e t i e s of P run us
av iu m . Bot. Gaz. 94: 433-468.
98.

. 1934. G row th of the p e a c h e m b ry o in r e la tio n to grow th of
f r u it and s e a s o n of rip e n in g . P ro c. A m e r. Soc. H ort. Sci. 30: 209218.

99.

. 1936. G row th of the em b ry o , seed, and p e r i c a r p of the s o u r
c h e r r y (Prunus c e r a s u s ) in r e la tio n to s e a so n of fru it ripening. P roc.
A m e r . Soc. H ort. Sci. 31: 125-144.

106 .

100. Tukey, H. R 1935. D evelopm ent of c h e r r y and p e a c h f r u i t s a s affected
by d e s tr u c tio n of the e m b ry o . P ro c . A m e r. Soc. H ort. Sci. 33: 265266.
101. ____________ . 1936. D evelopm ent of c h e r r y and p e a c h f r u i t s a s affected
by d e s tr u c tio n of th e e m b ry o . Bot. G az. 98: 1-24.
102.

, and J. O. Young. 1942. G r o s s m orp ho lo gy and histo log y
of developing f r u it of the apple. Bot. Gaz. 104: 3-25.

103. Van O v erb eek , J. 1952. A g r ic u ltu r a l ap p licatio n of gro w th r e g u l a t o r s
and t h e i r p h y s io lo g ic a l b a s is . Ann. Rev. Plant Physiol. 3: 87-108.
104. _ _ _____________ , G. D av ila-O liv o and E. M. Santiago de V azquez. 1945.
A r a p i d e x tr a c tio n m eth o d fo r f r e e auxin and its a p p licatio n in geotr o p i c r e a c t io n s of b ean s e e d lin g s and s u g a r - c a n e nodes. Bot. Gaz.
106: 440-451.
105. W atson, D. P. 1952. E ffect of elgetol s p ra y s on p i s t i l s of apple flo w e rs .
P ro c . A m e r . Soc. H ort. Sci. 60: 151-154.
106. W estwood, M. N. 1956. C h em ical thinning of p e a c h e s and a p r ic o ts .
W ash. State H o rt. A ssn . P ro c . 52: 100-102.
107. W ittw er, S. H. 1943. G row th h o rm o n e p ro d u c tio n d u rin g sexual r e p r o ­
duction of h ig h e r p la n ts . Mo. A gr. Exp. Sta. R e s. Bui. 371.