ANATOMICAL A SPECTS OF SOME ORNAMENTAL
P L A N T S SUB JECTED TO SPECIFIC TRANSPLANTING TECHNIQUES

By
F r e d B. W idm oyer J r .

A THESIS
Subm itted to the School of G raduate Studies of M ichigan
State College of A g r ic u ltu r e and Applied Science
in p a r t i a l fu lfillm e n t of the r e q u ir e m e n ts
fo r the d eg ree of
DOCTOR OF PHILOSOPHY

D e p a rtm e n t of H o rtic u ltu re
1954

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ACKNOWLEDGMENTS

The a u th o r w is h e s to e x p r e s s h is s in c e r e a p p r e c ia tio n
to D r . Donald P . W atson, u n d er whose d ir e c tio n th is i n ­
v e s tig a tio n was u n d e rta k e n .
G ra te fu l acknow ledgm ent is e x p r e s s e d to D r s . Alvin
L. K enw orthy, Leo W. M e r ic l e , and C. R. Megee as
m e m b e r s of the guidance c o m m itte e ; to D r. Donald H.
Dewey f o r h is guidance and valu ab le help in the c o lle c tio n
of d a ta and t h e i r a n a l y s e s .

The in v e s tig a to r extends his

s in c e r e th a n k s to M r . H aro ld H icks of Cottage G ard en s
N u r s e r y fo r th e u s e of abundant p la n t m a t e r i a l s .
H is th a n k s a r e a lso due to M iss Adele E d w a rd s for
h er assista n c e .

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

1

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

3

T r a n s p la n tin g

...............................

G rowth R e g u l a t o r s ...................................
D e s ic c a tio n

3
6

................................

P R O C E D U R E ..........................

15
25

Vacuum T r e a tm e n t of Woody P l a n t s ..................

26

Vacuum T r e a tm e n t of L y c o p e r s ic u m

. . . .

28

Soaking Woody P la n t s . . . . . . . . . . . .

29

Vacuum T r e a t m e n t of Annual F lo w e rin g P la n t s

29

P o ly eth y len e c o v e rin g on Thuja o c c id e n ta lis

30

RESULTS

......................

34

V acuum T r e a tm e n t of Woody P la n t s . . . . .

34

Vacuum T r e a tm e n t of L y c o p e r s ic u m

. . . .

36

Soaking Woody P l a n t s ......................

. . . .

38

V acuum T r e a tm e n t of Annual F lo w e rin g P la n t s

39

P o ly eth y len e C o v erin g on Thuja o c c id e n ta lis

43

A n a to m ic a l D e s c r ip tio n s . . . . . . . . . . .

48

DISCUSSION OF RESULTS . . „ . . 0 . ...............................

. .

68

V acuum T r e a t m e n t of Woody P l a n t s ................................ .

68

V acuum T r e a t m e n t of L y c o p e r s ic u m

. . . . . . . .

70

V acuum T r e a t m e n t of Annual F lo w e rin g P la n t s . . .

71

P o ly e th y le n e C o v erin g on T huja o c c id e n ta lis . . .
A n a to m ic a l D is c u s s io n s

.............................................

a

71
80

S U M M A R Y ...........................................................................................................

82

B IB L IO G R A P H Y ...................................

87

LIST OF TABLES
T A B LE

P ag e

1.

The L o ca tio n of the T h e rm o c o u p le s . . . . . . . . .

32

2.

T im e and T e m p e r a t u r e T r e a tm e n t , Thuja o c c id e n ­
. .
ta l i s cv. N i g r a ......................

33

3.

4.

5.

L en g th and A m ount of Growth a s Influenced by
V acuum T r e a t m e n t
....................................................

35

Yield of F r u i t L y c o p e r s ic u m e s c u le n tu m c v s . Red
C h e r r y and Golden Q u e e n ................................................

37

Weight of F r u i t L y c o p e r s ic u m e s c u le n tu m c v s , R ed
C h e r r y and Golden Queen
...............................

38

6.

Influence of Soaking on G rowth

7.

L e a f A r e a s a s Influenced by V acuum T r e a tm e n t

8.

N u m b er of L e a v e s and S tem s a s Influenced by
V acuum T r e a t m e n t ....................................................

9.

10.

.............................................
. .

40
41

42

P r e c i p i t a t i o n M a y -O c to b e r 1953 C o m p a re d to 3 0 -Y e a r
A v erag e
............................................................

69

V apor P r e s s u r e D eficit a s R e la te d to R e la tiv e
H u m id itie s a t D iffe re n t T e m p e r a t u r e s . . . .

74

11.

Open A ir T e m p e r a t u r e s for 25 D ays M a rc h 1954

75

12.

Soil T e m p e r a t u r e s at 2 1/2 Inch Depth fo r 25 Days
M a r c h 1954 .............................................................................

13.

14.

. .

76

A ir T e m p e r a t u r e s Under N o n - p e r f o ra te d T r a n s ­
p a r e n t P o ly eth y len e C o v er fo r 25 Days
M a r c h 1954 ...............................................................
A ir T e m p e r a t u r e s Under P e r f o r a t e d T r a n s p a r e n t
P o ly eth y len e C o v er fo r 25 Days M a rc h 1954

77

78

LIST OF FIGURES
FIG U RE
1.

T e m p e r a t u r e and R e la tiv e H um idity of Open A ir . .

2.

F o u r Day A v e ra g e of T e m p e r a t u r e - R e l a t i v e H u m i­
dity of A ir E n c lo s e d Under P e r f o r a t e d P o ly eth y len e
..........................................................
C o v er

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

Page
45

46

F o u r Day A v erag e of T e m p e r a t u r e - R e l a t i v e H u m i­
dity of A ir E n c lo s e d U nder N o n - p e r f o r a te d P o l y ­
........................................................................
eth ylen e C ov er

47

T r a n s v e r s e S ection of Stem and L e a v e s of Thuja
o c c id e n ta lis cv. N ig ra One Cm f r o m Apex (X80) . .

49

T r a n s v e r s e Section of Stem and L e a v e s of Thuja
o c c id e n ta lis cv. N ig r a One Cm f r o m Apex (X240). .

50

T r a n s v e r s e Section of O u ter L a y e r s of C ells of
L e a f of Thuja o c c id e n ta lis cv. N i g r a ................................

53

T r a n s v e r s e Section of 3 L e a v e s and S tem s, Showing
a L a r g e R e s in Duct (X80)
........................................

54

T r a n s v e r s e Section of Leaf, Showing a L a r g e R e s in
Duct ( X 2 4 0 ) .........................................................................

55

T r a n s v e r s e S ectio n of M a tu re L e a v e s and Stem of
T huja o c c id e n ta lis cv. N ig ra
. . . . . . . . . . . .

56

T r a n s v e r s e S ection of P a r t of L ea f and Stem of
Thuja o c c id e n ta lis cv. N ig ra Showing In ju ry D ev elo p ­
ing on O u ter Edge of E x p o sed L eaf
..................

58

T r a n s v e r s e S ection of P a r t of L e a f and Stem of
Thuja o c c id e n ta lis cv. N ig ra Showing In itial Stages
of D e h y d ra tio n on P la n ts in the Open F ie ld (X80). .

59

L e a f of Thuja o c c id e n ta lis cv. N ig ra Showing In itia l
S tages of D e h y d ra tio n on P la n ts in Open F ie l d (X240)

60

13.

14.

15.

16.

T r a n s v e r s e S ection of M a tu re S tem and L e a v e s of
T huja o c c id e n ta lis cv. N ig ra Showing S e rio u s D e ­
h y d ra tio n . ' . . . ............................................

63

T r a n s v e r s e Section of S tem and L e a v e s of Thuja
o c c id e n ta lis cv. N ig r a Showing In ju ry f r o m F r e e z i n g

64

T r a n s v e r s e S ection of L e a v e s and S tem s of Thuja
o c c id e n ta lis cv. N ig r a Showing In ju ry f r o m D ehy­
......................
d r a tio n a t 140°F (X80). . . . . . .

66

T r a n s v e r s e Section of L ea f and Stem of Thuja
o c c id e n ta lis cv. N ig ra showing In jury f r o m Dehyd r a tio n at 140°F (X240)..............................................................

.

67

INTRODUCTION

N u r s e r y grow n t r e e s and s h ru b s u s u a lly m ak e little grow th
the f i r s t y e a r a f te r tr a n s p l a n tin g .

N u m e ro u s o b s e r v a tio n s have

shown th a t th is la c k of grow th m a y be c a u s e d by the difficulty of r e ­
e s ta b lis h in g the ro o t s y s te m ( E m e r s o n and H ild re th , 1933; P r id h a m ,
1941; S w a rtle y , 1941; and G o s s a r d , 1942).
V a rio u s h o rm o n e p r e p a r a t i o n s have b een shown to i n c r e a s e
ro o t quantity on p la n ts ( H a r r is o n , 1937; M itc h ell, 1938; Smith, 1938;
G o s s a r d , 1942; and D o ran , 1952).

On

som e p la n ts r o o ts have been

p ro d u c e d m o r e abundantly, a s w ell as m o re ra p id ly , when the h o r ­
m one s u b s ta n c e s w e re applied to the v eg etativ e p a r t s .

S w artley

(1941) and N agato and Sato (1952) have r e p o r t e d m o r e r a p id ro o t
d ev elo p m en t on a l r e a d y ro o ted p la n ts which w ere soaked at t r a n s ­
p la n tin g tim e with h o r m o n e s .
A n u m b e r of p la n ts a r e m a r k e te d with a heavy bulk of soil
s u rro u n d in g th e ir r o o ts .

Since soil weighs about 100 pounds p e r

cubic foot, the p la n t is d ifficult to handle, and the r o o t s y s te m
is fre q u e n tly b ro k e n and b r u is e d , cau sin g difficulty in
ta tio n into the la n d s c a p e .

it s r e h a b i l i ­

M ille r , N eilso n and B an d em er (1937),

and G a r t n e r , O rR o u rk e and H a m n e r (1949) have s u c c e s s fu lly t r a n s ­
p la n te d p la n ts without having th e ir r o o ts su rro u n d e d by so il.

This

z

m e th o d of tr a n s p la n tin g h as not b een a g e n e r a l p r a c t i c e fo r
l a r g e r v a s c u la r p la n ts , but is often u s e d fo r young n u r s e r y
sto ck (T hom pson, 1940).
Follow ing tr a n s p la n tin g , it is b e lie v e d th a t r o o t and top
d e s ic c a tio n is one of the m a jo r c a u s e s of death.
The p r e s e n t in v e stig a tio n was u n d e rta k e n to study
(1) the a n a to m ic a l a s p e c ts of vacuum t r e a t m e n t as a p o s s ib le
m eth o d to r e d u c e the weight of tr a n s p la n tin g stock; (Z) effects
of in d o leace tic acid f o r c e d into the plant; (3) the effects of the
use of polyethylene film a s a co v erin g to p r e v e n t d e s ic c a tio n
of Thuja o c c id e n ta lis cv. n ig r a during the late w in ter and e a r ly
s p rin g .

L IT E R A T U R E REVIEW

T ra n sp la n tin g :
E v en though tr a n s p la n tin g of o r n a m e n ta l p la n ts has b een
a co m m o n p lac e o p e r a tio n fo r y e a r s , r e p o r t s of high m o r t a lit y
r a t e s of tr a n s p l a n te d stock a r e com m on.

G re g o ry , Im le, and

C am acho (1953) r e p o r t e d high l o s s e s d esp ite the fact th a t g r e a t
c a r e w as given to digging and planting of H evea b r a s i l i e n s i s .
In addition, they d efo liated and p ru n e d the cro w n to b alan ce the
r e d u c e d r o o t s y s te m .
T r a n s p la n tin g e x p e r im e n ts involving v a rio u s s p e c ie s of
e v e r g r e e n s by E m e r s o n and H ild re th (1933) r e s u l t e d in m o r t a lit y
r a t e s as high a s 100 p e r c e n t.

They a ttr ib u te d the l o s s to

(1) c lim a tic f a c t o r s fa v o ra b le to high t r a n s p i r a tio n ; (2) the n e c e s ­
sity of m oving the p la n ts in full foliage; and (3) the slow r a te of
r o o t r e g e n e r a tio n .
T r a n s p la n tin g s e r io u s ly re d u c e d grow th of Q u e rc u s p a l u s t r i s
( P r id h am , 1941).

It w as concluded th a t the re d u c e d grow th could not

be a t tr ib u te d e n t ir e ly to ro o t and top pru n ing , but th a t the s ea so n ,
so il, and the c a r e in handling w ere im p o r ta n t f a c t o r s .
A c c o rd in g to W hitten (1919), the m a jo r ity of in v e s t ig a to r s
have re c o m m e n d e d th a t p la n ts be m oved in the s p rin g .

Thom pson (1940)

4.

s ta te d th a t som e a u t h o r i tie s r e c o m m e n d e d fa ll, some w in te r, and
som e s p rin g , and s til l o th e r s pointed out th a t p la n ts m a y be m oved
s u c c e s s f u lly a t any s e a s o n of the y e a r .

He s ta te d , f u r t h e r , th at

although p la n ts w e re m oved e v e ry m onth of the y e a r , g r e a t e r i n ­
ju r y would o c c u r if the p la n t was d is tu r b e d durin g its p e r io d of
r a p id grow th.
In an e ffo rt to r e d u c e in ju ry and to lengthen the tr a n s p la n tin g
se a s o n , M ill e r , N e ilso n and B a n d e m e r (1937) r e p o r t e d th at by s p r a y ­
ing the top s with a wax em u ls io n they w e re able to tr a n s p l a n t the
following b a r e - r o o t s p e c im e n s s u c c e s s fu lly in July: P i c e a A b ies,
A c e r p a lm a tu m cv. d i s s e c t u m , Ulmus a m e r i c a n a , P o pu lu s n ig r a cv.
italic a and Syringa v u l g a r i s .
T ra n s p la n tin g e x p e r im e n ts conducted in 1949 by G a r tn e r , O 'R o u rk e
and H a m n e r m a d e u s e of a p r o te c tiv e c o v e rin g of vinyl r e s i n la tex
s p r a y e d on the fo liag e.

Both s p ra y e d and u n s p ra y e d t r e e s of P i c e a alba

t r a n s p l a n te d in June declin ed in g e n e r a l v ig o r, but the t r e a t e d t r e e s
w ere alw ays in b e t t e r condition than a c o m p a ra b le n u m b e r of c o n tr o ls .
They found th a t a ll deciduous p la n ts did not re s p o n d a lik e .

B e c h te l's

flo w erin g c r a b (M alus i o e n s i s ) and lila c (Syringa Spp) showed sy m p to m s
of gro w th inhibition, a cc o m p an ie d by the a b s c is s io n of som e le a v e s .
It was in d ic a te d th a t c e s s a ti o n of grow th as a r e s u l t of tr a n s p la n tin g
was p ro lo n g ed by the ap p lic a tio n of the p la s tic r e s i n , but tha t the

5

p la n t u s u a lly re g a in e d any lo s s of gro w th by a m o r e v ig o ro u s p r o ­
duction of new shoots a f te r grow th was r e s u m e d .
A no th er m eth o d of o v e rc o m in g the lo s s of vigor and to p r o ­
duce r a p id r e e s t a b l i s h m e n t of the p la n t was the use of s t a r t e r so lu tio n s.
S ta ir and H a r tm a n (1939) found th at by usin g n u tr ie n t so lutio n s in the
t r a n s p la n tin g w a te r for to m ato ( L y c o p e rs ic u m escu len tu m ) p la n ts , they
w e re able to in c r e a s e slig htly the e a r ly y ie ld s.

They w e re unable to

show s ig n ific a n t d iffe re n c e s betw een tr e a t m e n t s fo r to ta l y ie ld s .
S im ila r r e s u l t s w e re obtained by S ayre (1939).
It was b e lie v e d by Thom pson (1940) th a t in g e n e r a l a w e l l - b a l ­
an ce d fib ro u s ro o t s y s te m was p ro b ab ly the m o s t im p o rta n t single
f a c to r for s u c c e s s in tr a n s p la n tin g .

One m eth o d of in c r e a s in g the t r a n s ­

p lanting bulk of r o o ts of a t r e e was ro o t pru n ing w ell ah ea d of the tim e
of tr a n s p la n tin g .

To d e m o n s tr a te the f e a s ib ility of th is p r o c e d u r e ,

F a u lk n e r (1953) r o o t p ru n e d o n e - y e a r - o l d " C o r s ic a n " pine seed lin g s .
He found th a t r o o t pru n in g m a rk e d ly i n c r e a s e d the p ro d u c tio n of the
fib ro u s r o o ts in the soil above the point of ro o t s e v e r a n c e .
Neff and O 'R o u rk e (1949) p r e s e n te d data which in d icated th a t
t r a n s p l a n te d tung t r e e s (A le u r ite s F o r d ii) tended to m ake top growth,
followed by r o o t grow th.

They concluded th at p r o p e r c u ltiv a tio n e x e r te d

p e r h a p s the g r e a t e s t influence in m in im iz in g the decline in the grow th
r a t e a s d eficien t m o i s t u r e m a rk e d ly checked top growth.
A c c o rd in g to Goff (1897), f a ilu r e of a t r e e to r e s u m e grow th

following tr a n s p la n tin g was not alw ay s c a u s e d by in su fficien t m o i s ­
t u r e in the s o il.

W ater p r e s s u r e within the bud, supplied la r g e ly

th ro u g h r o o t p r e s s u r e c a u s e d the ex p an sio n of the le a v e s .

The u n d is ­

tu r b e d p la n t m a in ta in e d the r o o t p r e s s u r e by m e a n s of living r o o t
h airs.

By attac h in g one end of a r u b b e r hose to a r o o t 1/4 to 3 /8 inches

in d i a m e t e r , the opposite end of which was connected to a f la s k of d i s ­
ti lle d w a te r above the height of the t r e e , w a te r u n d e r p r e s s u r e was
sup p lied to the t r e e .

The buds of the t r e a t e d t r e e s expanded m o r e

r a p id ly than th o se of the u n tr e a te d t r e e s .

F ollow ing soil i r r i g a tio n ,

a l l t r e e s b egan grow th.

G row th H o rm o n e s:
G ustafson (1942) h as r e f e r r e d to his e a r l i e r p u b licatio n of
1936, in which he d is c lo s e d th a t in d o le a c e tic , in d o le p ro p io n ic , in d o le b u ty r i c , and p h en y lacetic a c id s induced s e e d le s s n e s s of m a tu r e f r u it s
by p la cin g la n o lin p a s te m ix tu r e on the style of u n pollinated flo w e rs of
L y c o p e r s ic u m e s c u le n tu m , P e tu n ia h y b r id a , and S alp ig lo ssu s varr-iabilis.
He s ta te d f u r t h e r th a t since th a t tim e m any c ro p s have b een added to the
l i s t of p a r th e n o c a r p ic f r u it p ro d u c tio n a s a r e s u l t of tr e a tin g with s y n ­
th e tic grow th s u b s ta n c e s .
H o rm o n e s have sin ce b een u se d to achieve o th e r r e s u l t s .
Z i m m e r m a n and H itchcock (1951) h as lis te d (1) the v eg etativ e p r o p a g a ­
tion of p la n ts by t r e a t m e n t of the cuttings and scions; (2) the p re v e n tio n
of p r e - h a r v e s t drop of f r u it, p a r t i c u l a r l y ap p les and o ra n g e s ; (3) the

7.

i n c r e a s e of f r u i t s e t and induction of p a r th e n o c a r p ic f r u it s ; (4) the
in h ib itio n of buds to p r e v e n t p otato and onion sp ro u tin g; (5) the in h i­
b itio n of f r u i t t r e e buds o r p ro lo n g in g d o rm a n c y to p r e v e n t lo s s by
la te f r o s t s ; (6) the inh ib ition of buds of n u r s e r y sto c k to p r e v e n t top
grow th u n til the young p la n ts a r e e s ta b lis h e d ; (7) re g u la tin g the f lo w e r ­
ing of v a r io u s c r o p s ; (8) the p r e m a t u r e d efo liatio n of p la n ts; (9) the
p re v e n tio n of a b s c i s s i o n a s c o n t r a s t e d to defoliation; (10) the c h e m ic a l
thinning of f ru it; and (11) the use of c h e m ic a ls as s e le c tiv e weed k i l l e r s .
He f o r e s a w the fu tu re need of bud inducing c h e m ic a ls in o r d e r to
f a c i lita te p r o p a g a tio n of plant p a r t s w h ere they w e re lo s t o r w here
buds had not a p p e a re d .
One of the m o r e p o p u lar m etho d s of a p p licatio n of h o rm o ne s u b ­
s ta n c e s h as b e e n to m ix it with lan o lin (Howlett, 1939; G ustafson, 1940;
A se n and H a m n e r, 1953).

The v ap o r m eth o d of a p p licatio n was i n t r o ­

duced by Z i m m e r m a n and H itchcock (1944).
a s p r a y e m u ls io n u s e d by W ithrow (1945).

A s i m i l a r m ethod is as
Cholodny (1936), S tier and

duBuy (1938), and T h im an n and Lane (1938) applied h o rm o n e s by s o a k ­
ing t h e seed in an aqueous solution containing the grow th r e g u la to r .
H a r r i s o n (1937) and Block (1938) dipped the p lan ts to be t r e a t e d in a
so lutio n containing the h o r m o n e s .

The ta lc m ethod, which is d e s c r ib e d

by D o ra n (1952) is u s e d e x te n siv e ly by p lant p r o p a g a t o r s .

A p p li­

c a tio n s of grow th r e g u l a t o r s w ere m ade to the soil by Randhawa

and T h o m p so n (1948) and S w artley (1941).

B e fo re tr a n s p la n tin g

r i c e s e e d lin g s (O ry z a sativa) Nagato and Sato (1952) soaked th e m
in a solu tio n containing naphthalene a c e tic acid .
L o c a liz e d a p p licatio n of h o rm o n e s u b sta n c e s was used
by R o m b e r g and Sm ith (1938) in tr a n s p la n tin g p e c a n (C ary a
i l l i n o e n s i s ) . T h is w as a c c o m p lis h e d by f i r s t soaking toothpicks
in a solution containing the grow th r e g u l a t o r .

H oles w ere b o re d

into the r o o ts and a toothpick plug in s e r t e d .
W atson (1948) and M itc h ell and Brow n (1946) in je c te d
m e a s u r e d am o u n ts of 2, 4 -d ic h lo ro p h e n o x y a c e tic acid into le af
t i s s u e f r o m a h y p o d erm ic n e e d le .
Conflicting r e p o r t s have b een re c o g n iz e d of the r e s p o n s e
of p la n ts to a p p lic a tio n s of h o rm o n e s .

H igher c o n c e n tra tio n s of

grow th r e g u l a t o r s have c a u s e d a g e n e ra l inhibition of growth, a
m o d ific a tio n of p a r t s as well as lo s s of the s m a l le r flow er buds
( Z i m m e r m a n and H itchcock, 1944).

In an e a r l i e r in v e stig a tio n

they found th a t fo r a few days following tr e a tm e n t the buds of
H ib iscu s s y r ia c u s g rew at equal r a t e s in a m e a s u r e d p e rio d .
The u p p e r m o s t shoots soon a f te r ap p licatio n g re w m o r e ra p id ly ,
inhibiting the lo w er b u d s.

R em oving the d is ta l tip of the ste m ,

s tim u la te d grow th of the inh ib ited sh o o ts.

N egative r e s u l t s w ere

9.

o b ta in ed by u sin g a c o n c e n tra tio n of 0. 5 p e r cen t in d o leacetic
a c id to induce r o o t f o r m a tio n on in ta c t p la n ts of T r a d e s c a n tia
v a lid a and Z e b r in a p endula (D o rfm u lle r, 1938).

A slig h t r e ­

ductio n in f r e s h weight of T a g e te s Spp„ , and a slig h t in c r e a s e
in w eight of P h a s e o lu s v u lg a r is v a r . B lack V alentine w as r e ­
p o r te d by M itc h ell (1938).

The t r e a t m e n t of one ppm in d o le ­

a c e tic a c id had no n o tic e a b le influence on the tim e of flo w erin g .
Z i m m e r m a n and H itchcock (1944) lik e w is e w e re
able to d e m o n s tr a te th a t even though h o r m o n e - t r e a t e d L y c o p e r s ic u m e s c u le n tu m f r u it grew f a s t e r th a n the c o n tro l, th e r e was
a d iffe re n c e am ong c u l t i v a r s .

The c u ltiv a r Globe w as m o re

s e n s itiv e th a n the c u l tiv a r s M arglo b e o r Bonny B e s t.

The d e v e l­

opm ent of photo synthetic a r e a and tim e of flo w er of c u ltiv a r
C o m e t h a s b e e n h a s te n e d by soaking the seed in a h o rm o n e s o lu ­
tio n u n d er g re e n h o u s e conditions (Thim ann and L ane, 1938).
Seedlings of O ry z a sa tiv a soaked in a solution of naphthalene
a c e tic acid b e fo re tr a n s p la n tin g w e re shown to have th e i r r o o t
grow th r e t a r d e d f o r one o r two days (Nagato and Sato, 1952).
Follow ing th is p e r io d r o o t growth w as h a s te n e d and th is effect
w as d im in is h e d g ra d u a lly u n d er fa v o ra b le grow ing conditions
w hich c a u s e d f a s t e r p ro d u c tio n of t i l l e r s , heading, and h e a v ie r
f r u itin g , th an if the p la n ts had not b een t r e a t e d .

Root p ro d u c tio n

10.

on p eca n , although not n a m ed a s such in the p u b licatio n , it was
a s s u m e d to be C a r y a i l l i n o e n s i s , was s u b s ta n tia lly in c r e a s e d
by lo c a liz e d a p p lic a tio n s of in d oleb u ty ric acid by in s e r tin g
w e ll-s o a k e d to oth pick s into the r o o ts (R om berg and Smith, 1938
and G o s s a r d , 1943).

Rooting r e s p o n s e was g r e a t e r in the

younger t r e e s , with the h ig h e r c o n c e n tra tio n s p ro d u cing the
g r e a t e s t r e s p o n s e (R o m b erg and Smith, 1938).

H a rriso n

(1937) ob tain ed s i m i l a r r e s u l t s when t r e a tin g I r e s in e lin d en ii
with in d o le a c e tic acid .

Root and s te m developm ent h as been

shown to have b e e n s tim u la te d by h o rm o n e tr e a t m e n t on young
p la n ts of som e s p e c ie s of the following g en era:
L o n ic e r a , M alu s, J u n ip e r u s , C o r e o p s i s , V io la, In c a rv ille a ,
L y c o p e r s i c u m , and C a llis te p h u s (Sw artley, 1941).
Z i m m e r m a n and H itchcock in 1942, using tr iio d o benzoic a c id c a u s e d the lo s s of the a p ic a l dom inance of
L y c o p e r s ic u m e s c u le n tu m and p ro d u c e d an a b n o rm a lly la rg e
n u m b e r of a x i lla r y leafy b r a n c h e s .

Using the sa m e m a t e r i a l ,

A se n and H a m n e r (1953) have in c r e a s e d the nu m b er of b a s a l
shoots on R o sa h y b rid a cv. B e tte r T im e s .
Thim ann (1937) r e p o r t e d th a t v e r y low c o n ce n tratio n s

11.

of auxins have a c c e le r a t in g effects on the v eg eta tiv e p o r ­
tio n s of the p la n ts .

P h a s e o lu s v u lg a ris cv. C alap p ro v ed

i n c r e a s e d in d ry weight, a b s o r p tio n of w a te r and d i r e c t ­
ional sh ifts of la r g e am o u n ts of n itr o g e n and c a r b o h y ­
d r a t e s f r o m le a v e s and cotyledons in c o m p a r is o n to the
c o n tro ls (S tuart, 1938).

Inhibition by the p r e s e n c e of the

grow ing ap ex of P h a s e o lu s v u lg a ris was d e m o n s tr a te d by
Snow, 1925.

When the apex was r e m o v e d o r p re v e n te d f r o m

grow ing, one o r m o r e p ro x im a lly lo c ated a x i lla r y buds
b eg an grow th.

Yitis sp. cuttings of 31 v a r i e t i e s , a f te r t r e a t ­

m e n t with v a r io u s grow th r e g u l a t o r s , showed v a r ia b le r e ­
s u lts of ro o tin g (H arm on, 1943).

In c o n s is te n t and non-

co n clu siv e r e s u l t s w e re r e p o r t e d by Leibundgut (1950) on
grow th of r o o ts and shoots of h o r m o n e - t r e a t e d f o r e s t t r e e
seeds.
The tap ro o t and l a t e r a l r o o ts of Hevea
b r a s i l i e n s i s w ere t r e a t e d with naphthalene a c e tic acid in
c o n c e n tr a tio n s of 0. 5 p e r cent and 1 p e r cent by G re g o ry ,
Im le, and C am ach o (1953).

F r o m th is ap p licatio n they

concluded th a t NAA helped i n c r e a s e the d e g re e of s u r v iv a l

of th e tr a n s p l a n te d t r e e s .
A v a r ie ty of r e s p o n s e s of the y ield of f r u i t
m ay be ex p ected f r o m h o rm o n e t r e a t m e n t .

S tie r and duBuy

(1938) in c r e a s e d the e a r l y and to ta l y ie ld s of m a r k e ta b le
L y c o p e r s ic u m e s c u le n tu m f r u it by soaking the seed in v a r io u s
h o rm o n e s o lu tio n s.

Seed of Avena sa tiv a , which was soaked

in a solution of in d o leacetic a c id b efo re sowing, p ro d u c e d
p la n ts on which the yield of seed p e r p lant was i n c r e a s e d by
55 p e r cen t (Cholodny, 1936).

A c o n c e n tra tio n of 0.2 5 m g

of 4 - p h th a lim id o -2 , 6 -d im e th y l p y rim id in e p e r l i t r e was
found to in c r e a s e the e a r l y yields of L y c o p e r s ic u m esc u le n tu m
when c o m p a r e d with t r e a t m e n t s which a r e g e n e r a lly acc e p te d
m eth o d s of h a rd e n in g ( L e a r n e r , 1952).

T h e re was a ls o an

i n c r e a s e in the to ta l n u m b e r of rip e f r u it h a r v e s te d .
W ithrow (1945) tr e a tin g L y c o p e r s ic u m e s c u l ­
entum c u l tiv a r s Long Calyx and M ichigan State F o r c in g with
grow th r e g u l a t o r s and growing th e m in the g reen h o u se f r o m
A p r il to Ju ly , r e p o r te d the fo r m a tio n of m o r e f r u it on the
e a r l y c l u s t e r s , but found little d ifferen c e in to ta l p ro d u ctio n .
F ie ld - g r o w n p la n ts p ro d u ced p r a c t ic a l ly no
d iffe re n c e in yield a f te r having b een t r e a t e d ( Z im m e r m a n

and H itchcock, 1944).

The sa m e p la n t w a te r e d a t t r a n s ­

p lan tin g tim e with a c o n c e n tr a tio n of 50 mg naphthalene a c e tic a c id in 50 gallons of w a te r s u ffe re d a re d u c tio n of
e a r l y f r u i t (S ayre, 1938).

When five tim e s as m uch h o r ­

m one was applied, th e r e was an even g r e a t e r delay on
date of m a tu r ity and a lo w er y ield.

S ayre concluded

th a t h o r m o n e s w e re m o r e effective in v e r y dilute c o n ­
c e n tr a tio n .

It would s e e m th at the chief benefit to be

d e r iv e d f r o m the use of h o rm o n e s on to m a to e s would be
the p ro d u c tio n of p a r th e n o c a r p ic f r u it s .
M o rphological and h is to lo g ic a l d iffe re n c e s
o c c u r r e d in p la n ts which had b e e n t r e a t e d with h o r m o n e s .
R e s p o n s e s d iffe re d with the s p e c ie s of the p lant, and the
c o n c e n tr a tio n of the h o rm o n e .

A g e n e r a l re v ie w of the

l i t e r a t u r e to the p r e s e n t h as been m ade by B eal in 1951.
H o rm o n es ap p lied to r o o ts ,

s te m s , le a v e s , flo w e rs or

f r u i t s w e re r e a d ily a b s o r b e d by the p la n ts (M itchell, 1951).
It had b e e n poin ted out p r e v io u s ly by M itchell and Martin^
1938, th a t in P h a s e o lu s v u lg a ris m a r k e d m o rp h o lo g ical
d if f e r e n c e s o c c u r r e d following t r e a t m e n t with in d o leacetic

14

a c id .

In d o lea cetic a c id , when ap p lied to L y c o p e r s ic u m

e s c u le n tu m did not in h ib it the d ev elo p m ent of buds below
the t r e a t e d a r e a .

R e s p o n s e s w e re s i m i l a r to those of

P h a s e o lu s sp. , ex cep t in L y c o p e r s ic u m esc u le n tu m ,
which w as explained on the b a s i s of the p r e s e n c e of i n t e r ­
n al p h lo em in th is p la n t (Borthw ick, H a m n e r, and P a r k e r ,
1937).
In r e s p o n s e to v a rio u s grow th r e g u la to r s
H ib isc u s s y r i a c u s , a c c o rd in g to Z i m m e r m a n and H itchcock
(1940) u su ally p ro d u ced new adv en titio us buds a s s o c ia te d
with the x y le m p oints which extended into the b a r k .
P o p u lu s g e n e r o s a did not re s p o n d in a s i m i l a r m a n n e r .
The grow th of a x i lla r y buds of T r a d e s c a n tia
f lu m in e n s is was s u p p r e s s e d by dipping the p la n ts in an
aqueous so lu tio n of in d o leb u ty ric a c id

(Block, 1938).

He also r e p o r t e d th a t in the r a p id ly elongating p a r t s of
the shoot, s h o r t th ick s e g m e n ts w ere f o rm e d in the b a s a l
p a r t of the in te rn o d e .

The d iffe re n tia tio n p r o c e s s e s

w e re in itia te d p r e m a t u r e l y and m o r e v ig o ro u sly .

Thi s

r e s u l t e d in the f o r m a tio n of n u m e ro u s , f a s c ia te d , i n t e r ­
n al r o o ts a s w ell a s nodal v a s c u l a r e le m e n ts .
C ooper (1938) concluded th a t in d o leacetic
acid c o n tro lle d the m o v e m en t of s u b s ta n c e s in the cu ttin g s .
R em o v al of th e b a s e of a h o rm o n e t r e a t e d cutting, f o l ­
lowed by a second tr e a t m e n t ,

se e m e d to d e s tr o y the effect

of the t r e a t m e n t .

D esiccatio n :

M ey er and A n d e rso n (1952) have cautioned
the r e a d e r not to confuse w in ter killing, r e s u ltin g f r o m
d e s ic c a tio n with cold in ju ry , r e s u ltin g f r o m low t e m p e r a ­
t u r e s , which is a d iffe re n t phenom enon.
At t e m p e r a t u r e s slightly above fre e z in g ,
the r a t e and am o u n t of w a te r m o v e m e n t in p lan ts was
g r e a tly re d u c e d ( K ra m e r , 1940).
T hom pso n (1940) a ttr ib u te d in ju ry to c e r t a i n
deciduous and e v e r g r e e n p la n ts to d e s ic c a tio n by winds in

la te w in te r and e a r l y s p r in g .

He ex plained th a t th e winds

c a u s e d e x c e s s iv e t r a n s p i r a t i o n f r o m the foliage and tw igs
of a n u m b e r of d iffe re n t p la n ts b e fo re th e r o o ts w ere able
to a b s o r b su fficien t w a te r to r e p la c e th a t lo s t f r o m the
leav es.

T his is c o n firm e d by B r i e r l e y (1934) fo r Rubus

sp. , and P ir o n e (1950) fo r s p e c ie s of Rhododendron, Ilex,
P in u s , P ic e a , and A b ie s .

R o e s e r (1932) h as shown th a t

see d lin g s of P in u s p o n d e r o s a and P in u s c o n to rta cv,
la tif o lia lo s t th i r t e e n , P s e u d o ts u g a D ouglasii, eighteen,
and P i c e a E n g e lm a n n ii, tw e n ty -e ig h t ti m e s m o r e w a te r
at 51°C th a n a t 16°C.
F u r t h e r s u b sta n tia tio n of w a te r lo s s
being r e s p o n s ib le fo r in ju ry was advanced by B r i e r l e y
and Landon (1946).

L a th a m r a s p b e r r y h as b een highly

r e s i s t a n t to t e m p e r a t u r e s as low as m in u s 4 5 ° F , but lias
o
b een s e v e r e ly in ju r e d by m in u s 8 F , following two days
at 3 7 . 4 ° F .

They fa ile d to m en tio n the r e la tiv e hum idity

or the va p o r p r e s s u r e d efic it of the a tm o s p h e r e fo r th is
e x p e r im e n t.

17.

Sunlight m ay ca u se e x c e s s iv e h eat or an e x ­
c e s s iv e l y high t r a n s p i r a t i o n r a t e .

D eath of t r e e s h a s o c c u r ­

r e d as a r e s u l t of high a i r t e m p e r a t u r e s r e s u ltin g f r o m poor
a i r d ra in a g e (Tourney, 1947).

He m a in ta in e d th at the am ount

of in ju ry a t any given t e m p e r a t u r e in c r e a s e d with i n c r e a s ­
ing len g th of e x p o s u re , and the h ig h e r the a i r te m p e r a t u r e
the s h o r t e r the p e r io d of e x p o su re r e q u i r e d to p ro d u ce
d eath of p la n t t i s s u e .
S h irle y (1936) m ad e the o b s e r v a tio n th at
stu d ie s of le th a l t e m p e r a t u r e s fo r c o n ife r s have been c o n ­
fined to the u s e of s e e d lin g s .

T hese r e s u l t s v a r ie d c o n s id ­

e ra b ly , depending on the m etho d s
of the e x p o s u r e .

u se d and the d u ra tio n

L e a v e s w ere m o r e exposed to d ir e c t s u n ­

lig h t, and w ere m o r e com m only in ju re d than the o th er
p a r t s of the p lan t, p ro v id in g it had developed beyond the
ju v e n ile condition.
K ozlow ski (1943) found no g r e a t d iffe ren c e
in the t r a n s p i r a t i o n r a t e of co n ife r and deciduous s p e c ie s
on a unit a r e a b a s i s .

S c r e e n s of ca n v a s, b u r la p , r u s tic - w o v e n
s tr a w and s ta k e s w e re s u g g ested by T hom pson (1940) to
r e d u c e w a te r lo s s f r o m p la n ts .

F o lia g e and blo o m s of

G la d io lu s , D ahlia, A n th irrh in u m , and C a llis te p h u s w ere
f r e e of s u n - s c a ld when grown u n d er c h e e s e c lo th e n c lo s u r e s
(B atson, 1933).
Wiegand (1906) d e m o n s tr a te d th a t white
p ain t ap p lied to tr u n k s of p eac h t r e e s r e d u c e d the t e m p e r ­
a t u r e 15°C.
White, H o r s f a ll, and T a l b e r t (1933) a tte m p te d
to p r o t e c t p la n ts by the u s e of a r e s i n e m u ls io n to which he
added s h o r t a s b e s to s f i b e r s .

E x ce p t fo r the white c o lo r, he

concluded th a t the m a t e r i a l was of doubtful value.

Wax e m ­

u ls io n s w e re u se d s u c c e s s f u lly to re d u c e w a te r lo s s and to
p r e v e n t dam age to the p la n ts by M ille r , N e ilso n and B a n d e m e r
(1937).

G a rd n e r (1944) o b s e r v e d that o il-w ax e m u ls io n a p p l i­

catio n s r e d u c e d w a te r lo s s 20 to 60 p e r cent.

This red u c tio n

depended upon the s p e c ie s , the conditions of the e n v iro n m e n t,
and the c o n c e n tr a ti o n of the em u lsio n .
T h e r e w e re no a p p a re n t in ju rio u s effects on

th e fo liag e when suita b le dilutions w e re u s e d .

McMahon in

1947 m a d e a c o m p a r is o n b etw een the use of a wax e m u ls io n
and p lio film c o v e r to r e d u c e the r a t e and quantity of t r a n s ­
p ir a t io n of f r u i t in s to r a g e .
m o r e effec tiv e .

He concluded th a t p lio film was

Sherwood and H am n er (1948) u se d "Geon 31"

to len g th en the life of cut b r a n c h e s of e v e r g r e e n s and some
c o m m e r c ia l cut f lo w e r s .

A vinyl r e s i n la te x was sp ra y e d

on P i c e a a lb a (G a r tn e r , O fR ourke and H a m n e r, 1949).
One m onth a f te r t r e a t m e n t and tr a n s p la n tin g w ithout a d d i ­
tio n al w a te r , all u n s p ra y e d p la n ts w e re dead, while 25 p e r
cent of the t r e a t e d p la n ts su rv iv e d .
P l a s t i c f ilm s developed f r o m high p o ly m e r s
of ethylene a r e p o p u la rly known as "p o ly ethen e" o r " p o ly ­
e th y le n e " .

Sweet (1953) found th a t m o i s t u r e was c o n s e rv e d

when polyethylene film w as u s e d to w rap the rooting m e d iu m
of cu ttin g s o r s e e d lin g s .
H a m n e r , C a r l s o n and Tukey in 1945 r e p o r te d
th a t su ccu le n t p la n ts and cut flo w e rs w e re m a in ta in e d in a
tu r g id condition f r o m four to 36 h o u rs lo n g e r than co n tro l
p la n ts by su b m e rg in g th e m in w a te r, and evacuating the a i r

by m e a n s of a w a te r pum p to a p r e s s u r e of a p p r o x im a te ly
30 pounds p e r s q u a r e inch fo r 20 m in u te s .

A fter p a r t i a l

ev ac u atio n , the pump was tu r n e d off and the p r e s s u r e
g ra d u a lly i n c r e a s e d to th at of the a i r .
R. H. B u r r i s (1952,1953) em ployed the
tech n iq u e of i m m e r s i n g in ta c t le a v e s of p la n ts in a s o lu ­
tio n containing in h ib ito rs of p h o to sy n th e sis and th en e v a c ­
uating the a i r f r o m the c h a m b e r and the le a v e s .

N o rm a lly ,

he u se d a vacuum of 15 to 20 m m m e r c u r y r e s id u a l p r e s s u r e .
The le a f was in f iltr a te d by r e le a s in g the vacuum , cau sin g
the solution to p a s s into the in t e r c u ll u la r sp aces of the
le a v e s .

The extent of in f iltr a tio n was evidenced by the

change of the le a f f r o m an opaque to a t r a n s l u c e n t condition.
A fte r the le a v e s w e re re m o v e d , they w ere blotted d ry with
p a p e r tow els and the p e tio le s i m m e r s e d in a solution.

The

e x c e ss w a te r was t r a n s p i r e d , and the le a v e s then re g a in e d
and r e ta in e d th e i r n o r m a l opaque a p p e a ra n c e .

If the in f i l ­

tr a t i o n was too v ig o ro u s , the le a v e s w ilted a f te r the i n ­
f i l t r a t e d w a te r was t r a n s p i r e d .

S tentor and S p ir o g y r a , a c c o rd in g to the o b ­
s e r v a tio n s of G re e ly (1901) exhibited synonym ous a p p e a r ­
a n c e s c a u s e d by f r e e z in g , d e s ic c a tio n , and p la s m o ly s is .
Studying d e s ic c a te d Rubus c a n e s, Simonds
(1942) found th a t the c e ll w alls w e re not ru p tu re d , and th a t
siev e tube c o n ten ts a p p e a re d m o r e sh ru n k en than th o se in
tu r g id t i s s u e .

T h e r e w as a m a r k e d d ep o sitio n

of "tan n in -

lik e " m a t e r i a l , a re d u c tio n of s iz e , and a sh rin k ag e of the
co n ten ts of a ll living c e l ls e x t e r i o r to the c a m b iu m .

He

d is c o v e r e d p ro n o u n ced sp littin g of the a b s c is s io n l a y e r s .
Mix (1916) r e p o r t e d th a t the youngest xylem c e lls w e re the
f i r s t to be in ju re d , and th a t co m p lete killing could be
id en tified f r o m d is c o lo r a tio n of the c e l ls .

A cco rd in g to

P a r k e r (1951, 1952) som e h y p o d erm a l c e lls of the le a v e s
of P in u s s tro b u s had c o lla p s e d len g th w ise, while the
e n d o d e rm a l c e lls f la tte n e d out, and the tr a n s f u s io n tr a c h e id s
and p a r e n c h y m a had c o lla p s e d f r o m in ju ry .
was noted in the x y le m and phlo em c e l l s .

L ittle change

Using ex c ise d

le a v e s of P in u s s tr o b u s and P . n ig r a cv. A u s t r ia c a d e s i c ­
c ated a t r o o m t e m p e r a t u r e (20°C) and a r e la tiv e hum idity

22

of 60 p e r cent, P a r k e r (1952) found th a t the c e l ls of the
c h lo re n c h y m a , e n d o d e r m is , and tr a n s f u s io n t i s s u e d e c r e a s e d
in s iz e .

The ad ax ial s u r f a c e of th e le a f of the A u s t r ia n pine

b en t in w ard a s c o n t r a s t e d to a ll th r e e s u r f a c e s of the white
pine le a v e s a s a r e s u l t of th is s h rin k a g e .
M a c r a s c o p ic c o lo r changes in the le a v e s m ay
be c a u s e d , he p o s tu la te d , by the c o n tra c tio n of the c h l o r ­
en chym a.

Under the conditions of h is e x p e rim e n t, the le a v e s

of P in u s s tro b u s d r ie d c o n s id e ra b ly f a s t e r th an the P . n ig r a
cv. Au s tr ia e a.
A breakdow n of the n u c le a r o rg a n iz a tio n of
c e lls of P r u n u s

s te m s su b jected to the low t e m p e r a t u r e s of

the w in te rs of 1915-1916 and 1916-1917 was not a c c o m p a n ie d
by r u p tu r e o r b re a k in g a p a r t of c e ll w alls (D o rsey and
S trau sb au g h , 1923).

Browning was confined to the c o r ti c a l

c e lls containing c h l o r o p l a s t s , but in ju ry was of a m in o r
n a tu re .

In p la c e s w h ere in ju ry was s e v e r e , the v e s s e l s w ere

occluded by a y ello w -b ro w n m a s s of m a t e r i a l which was m o r e
p ro n o u n ced in o ld e r v e s s e l s .
In h is r e v ie w of l i t e r a t u r e , Clum (1926a; 1926b)
showed th a t p la n t t i s s u e s in b rig h t sunlight w ere at a h ig h e r t e m ­
p e r a t u r e than th a t of the s u rro u n d in g a i r , but th a t th e r e was wide

2

and r a p id flu c tu a tio n s even in p e r io d s of s h o r t d u ra tio n of
lig h t.

In h is w ork only a d iffe re n c e of 2 to 3°C was a ttr ib u te d

to t r a n s p i r a t i o n .

A c co rd in g to M ille r (1938), the a c tu a l k illing

t e m p e r a t u r e fo r m o s t p la n t p r o to p la s m h a s b een found to v a ry
betw een a high of 113 to 131°F.

LundegSrh (1931) o b s e r v e d th at

th e r e was c o n s id e r a b le v a r ia tio n am ong s p e c ie s in the d e g re e
of h e a t th a t they a r e able to w ithstand.

The h ig h e r the t e m ­

p e r a t u r e , the s h o r t e r p e r io d of tim e r e q u ir e d to p ro d u ce in ju ry .
S unscald w as g e n e ra lly c o n s id e r e d by C h an d ler in 1913 to be
the effect of heat a b s o r b e d in d i r e c t sunlight by the d a r k e r
c o lo re d tis s u e of the p la n t.

His o b s e rv a tio n s showed th a t the

r a t e of t e m p e r a t u r e d e c r e a s e g r e a tly influenced the k illing
e ffect.

In la te w in te r the t i s s u e s d ir e c tly exposed to the sun

ten ded to r i s e above f r e e z in g , while th o s e u n e x p o s e d tis s u e s on
the opposite side of a b r a n c h r e m a in e d clo se to ex istin g a t m o s ­
p h e r ic t e m p e r a t u r e s .

When the sun r a y s w e re no lo n g e r d ir e c tly

shining on the a l r e a d y w a r m e d p e r ip h e r y of a tru n k of a t r e e ,
the t e m p e r a t u r e quickly r e s u m e d an equilibrium with th at of the
su rro u n d in g a i r .
B ro o k s and F i s h e r (1926) d e m o n s tr a te d the t e m p e r a ­
t u r e d if f e r e n tia l betw een the exposed and the shaded s u rfa c e of the

24.

f r u i t of M alus p u m ila while they w ere a tta c h e d to the t r e e .
The ex p o sed side w as 10 to 16°F w a r m e r than the shaded sid e.
B la ck t a r - p a p e r c o v e rin g s on the tr u n k of f r u i t t r e e s in c r e a s e d
the t e m p e r a t u r e 10 to 2 5 °F above th a t of the a i r (Mix, 1916).
L e a v e s of N ic o tia n a sp. i n s e r t e d in cellophane envelopes i n ­
c r e a s e d in t e m p e r a t u r e f r o m 87 to 127°F.
n e c r o tic spots developed.

Two days l a t e r

A r th u r and S tew art (1933) d e m o n ­

s t r a t e d th at a s th e t e m p e r a t u r e a p p ro a c h e d the th e r m a l death
point f r o m e ith e r high r a d ia tio n o r high t e m p e r a t u r e , the
t i s s u e lo s t g r e a t q u a n titie s of w a te r .
P o t t e r (1936) concluded th a t in ju ry incident to
cold w eath e r m ig h t have b e e n c a u se d by d e s ic c a tio n of the
tissu e s.

A llen and A s a i (1943) c o n s id e r e d the chief p ro b le m

in growing g a r d e n r o s e s to be th a t of w in te r in ju ry .

They

a t tr ib u te d w in te r in ju ry to be c au sed by e x tre m e t e m p e r a t u r e
or d e s ic c a tio n of the t i s s u e .

Much of th e evidence of d e s i c c a ­

tio n a s a f a c to r of w in te r in ju ry h a s b een b a s e d on s u p e r f ic ia l
o b s e r v a tio n s .

W ilner (1952) found th at d e s ic c a tio n o c c u r r e d

m a in ly d u rin g p e r io d s with a t e m p e r a t u r e above f r e e z in g ,
o
e s p e c ia lly above 41 F .

PROCEDURE

One dozen R o sa h y b rid a cv. B e tte r T im e s flo w e rs
w e re cut at the P la n t Science g reen h o u se at 1030 h o u r s on May 21,
1953 at v a r io u s s ta g e s of bud d ev elo p m en t.
into hot w a te r (9 8 °F ).

They w e re plunged

A fter a p p r o x im a te ly four h o u r s , the s te m s

w ere cut to 10 in c h e s in length, and the flo w e r s w e re s e p a r a te d
into c o m p a r a b le g ro u p s .

Six flo w e r s w e re p la ced in a p y r e x g la s s

d e s s i c a t o r w ith a tig h tly fitte d c o v e r .

The flo w e rs w e re above the

w a te r, the p r o x im a l p o r tio n of the s te m s being held u n d er w a te r
by a heavy w eight.

A v acu u m of 20 m m m e r c u r y was draw n by

m e an s of a pum p in o r d e r to ev ac u ate the a i r th ro u g h a ground
g la ss valve in the c o v e r of the j a r .

The p r e s s u r e was eq u alized

g ra d u a lly (about 5 m in u te s ) to that of the a tm o s p h e r e .

As the

v acu u m w as r e l e a s e d , the w a te r p a s s e d into the le a v e s .

Vacuum

w as ap p lied s e v e r a l t i m e s until the foliage b eca m e w a te r - s o a k e d
in a p p e a r a n c e .

The flo w e r s w e re re m o v e d , allowed to d r a in on

p a p e r tow eling, then p la c e d in o n e -fo u rth pint j a r s of w a te r in the
la b o ra to ry .

F o u r days l a t e r , u n tr e a te d flo w e rs w e re wilting b e ­

f o r e p e ta l ex p an sio n .

The m a r g in s of the p e ta ls and the le a v e s w e re

d e s ic c a te d in c o n t r a s t to th o se which had been exposed to the
v acu u m .

The flo w e rs and foliage of th r e e u n id en tified c u ltiv a r s of S y rin g a v u lg a r is w e re exposed to a s i m i l a r t r e a t m e n t .

T ur-

gidity was m a in ta in e d as a r e s u l t of t r e a t m e n t for 36 h o u r s , an i n ­
c r e a s e of a to ta l of 34 h o u r s o v er those which w e re u n tr e a te d .

When

flo w e r s w e re u s e d in the t r e a t m e n t , but fa ile d to be co m p le te ly s u b ­
m e r g e d in w a te r , they showed no im p ro v e d keeping q u ality .
Two o n e - y e a r - o l d p la n ts of eac h of Syringa v u lg a r is cv.
T h un b erg , H y d ran g ea a r b o r e s c e n s g ra n d iflo ra and F o r s y t h ia s p e c ta b li s w e re su b jected to vacuum tr e a t m e n t .

As soon as the c e l ls of

the le a v e s a p p e a re d to change color as a r e s u l t of the e n tra n c e of
w a te r u n d er re d u c e d p r e s s u r e , the p la n ts w ere p lan ted in the g a r ­
den and no w a te r was added to th e so il.

Wilting w as not d is c e r n ib le

on F o r s y t h i a o r S y rin g a d u rin g the following week, but d iu rn a l w i l t ­
ing of the su ccu le n t grow th of H y d ran g ea o c c u r r e d r e g u l a r l y .

Sub­

s ta n tia l gain in weight was o b s e r v e d a s a r e s u l t of the t r e a t m e n t with
v acu u m .
V acuum T r e a tm e n t of Woody P la n ts :
O n e - y e a r - o ld p la n ts com m only c a lle d ,rlin in g -o u t stock*'
by c o m m e r c i a l p r o d u c e r s w e re obtained fr o m Cottage G ard en s N u r ­
s e r y of L an sin g , M ichigan on May 18, 1953.

The p la n ts w ere packed

w ith dam p sphagnum su rro u n d in g th e ir r o o ts and p la ced in a c o n tro lle d

t e m p e r a t u r e of 3 9 ° F fo r eight d ay s.

D uring th is p e r io d the p la n ts

w e re illu m in a te d , u sin g a low in te n s ity of in c a n d e s c e n t lig h ts .
The p la n ts w e re w eighed and a r b i t r a r y g ro u p s s e le c te d to co n tain
p la n ts weighing f r o m : 15 to 19 g m s, 20 to 24 g m s, and o v e r 25 g m s .
P l a n t s f o r ea c h t r e a t m e n t w e re s e le c te d so th at th e r e w e r e fo u r
r e p li c a ti o n s , te n p la n ts p e r t r e a t m e n t containing th e sa m e n u m b e r
of p la n ts f r o m eac h weight group.
An im p ro v e d equipm ent c o n s is tin g of a pump d esig n ed
to develop a m a x im u m vacuum of 20 m m of m e r c u r y and a ta ll
f l o r i s t s 5 m e ta l v ase of five l i t e r cap a city , w e re u s e d fo r s u b m e r g ­
ing the p la n ts .

T h is c o n ta in e r was p la ced on a vacuum pla te and

c o v e r e d with a p y r e x b e ll j a r .

During evacuatio n the p la n ts w e re

w eighted to p r e v e n t flo atin g .
The r o o ts of the 40 p la n ts w e re p la c e d in w a te r and
allow ed to r e m a i n d u rin g th e t r e a t m e n t of the o th e r g ro u p s .

F o rty

m o r e p la n ts w e re su b jected to a vacuum fo r 20 m in u te s while s u b ­
m e r g e d in ta p w a te r , and an ad d itio n al 40 p la n ts w ere su b jected
to the sam e v acu u m t r e a t m e n t using a solution of one ppm in d o le a c e tic a c id .
F ollow ing tr e a t m e n t , the p la n ts w ere s to r e d fo r 12
h o u rs at 39 d e g r e e s F b e fo re being planted in ra n d o m iz e d sequence

a t the H o r tic u l tu r a l F a r m of M ichigan State C o lleg e, spaced four
fe e t b etw e e n r o w s , and two fe e t a p a r t w ithin the ro w .

The soil

v a r ie d f r o m a H illsd a le sandy lo a m at one end of the ro w to a
silty lo a m at the o th e r.

At the tim e of tr a n s p la n tin g eac h plan t

r e c e i v e d t h r e e - f o u r t h s of a pint of w a te r .

In itial w eights of

the p la n ts and w eights a f te r t r e a t m e n t , l i n e a r m e a s u r e m e n t s
and n u m b e r of b r a n c h e s w e re r e c o r d e d a t the co n c lu sio n of the
growing s e a s o n .

V acuum T r e a tm e n t of L y c o p e rsic u m :
T r e a tm e n t s of L y c o p e r s ic u m esc u le n tu m cv.
Golden Queen and Red C h e r r y w e re id e n tic a l to th o se of Syringa
and F o r s y t h i a .

R oots of s e e d lin g s with 4 to 6 tr u e le a v e s w ere

w ash ed f r e e of soil, p la n ts s o r te d so th at all g roups of te n w e re
n e a r l y s i m i l a r , and t r e a t e d on June 3, 1953.

All p la n ts w ere

t r a n s p l a n te d to the field the following day in row s four feet a p a r t
with four fe e t b etw ee n p la n ts .

No s u p p le m e n ta ry w a te r w as s u p ­

p lied at the tim e of p lan tin g o r durin g the growing s e a s o n .

The

f r u i t w as h a r v e s t e d a t 4 -d a y in t e r v a ls f r o m A ugust 25 until O ctober
3.

The n u m b e r of f r u i t s and the to ta l weight of f r u it of each

t r e a t m e n t w as m a in ta in e d .

29.

Soaking Woody P l a n t s :
P la n t s of S y rin g a v u lg a r is cv. T h u n berg and F o r s y ­
th ia s p e c ta b ilis w e re soaked fo r two h o u r s in (a) tap w a te r and
(b) one ppm of in d o le a c e tic acid, (c) no soaking.

The p la n ts w e re

all t r a n s p l a n te d into the field f r o m m o i s t sphagnum pack in g .

Spac­

ing w as fou r fe e t by two fe e t a p a r t w ithin the row .
At the co nclu sio n of the growing s e a s o n , m e a s u r e ­
m e n ts w e re r e c o r d e d fo r the to ta l lin e a r grow th and the to tal
n u m b e r of b r a n c h e s .

Vacuum T r e a t m e n t of Annual F lo w e rin g P l a n t s :
Seeds of the following annual flo w erin g p la n ts w ere
sown in s t e r i l i z e d soil (two p a r t s co m p o sted lo am , one p a r t s h a r p
sand, one p a r t peat) in f la ts at the P la n t Science g reen h o u se on
D e c e m b e r 5, 1953: C a llis te p h u s c h in e n sis cv . Rem o and K irkw ell;
Salvia sp lend ens cv. St. J o h n rs F i r e ; G e n ta u re a cyanus cv. P inkie;
and T a g e te s p a tu la cv. D w arf Bedding.

The seed lin g s w e re t r e a t e d

as in vacu u m t r e a t m e n t of woody p la n ts , tr a n s p la n te d J a n u a r y 23,
1954 into 3 - in c h p o ts u sin g the sa m e soil m ix tu r e as fo r seeding.
F if te e n p la n ts of each c u ltiv a r w e re s e le c te d , divided into th r e e
g ro u p s of five p la n ts each .

The n u m b e r of le a v e s and le a f a r e a s of

two p la n ts w ere r e c o r d e d on F e b r u a r y 12 and M a rc h 6, 1954.

C a llis te p h u s w as grow n a t a g re e n h o u s e t e m p e r a t u r e of 50°F
with six h o u r s of s u p p le m e n ta r y in c a n d e s c e n t lig h t.

The r e ­

m a in d e r of the p la n ts w e re grow n at 6 0 ° F (night t e m p e r a t u r e ) .

P o ly e th y le n e C o v erin g of Woody P la n t s :
On F e b r u a r y 3, 1954, 40 p la n ts of Thuja o c c id e n t a l i s cv , n ig r a w e r e c o v e r e d with 0, 002 gauge polyethylene
film ’’C h e s le n e " m a n u fa c tu r e d by C h e s te r P a ck ag in g P r o d u c ts
C o r p o r a tio n , Y o n k ers, New Y ork.

O n e-h alf of the f ilm was

u n p e r f o r a te d , and the r e m a in d e r w as p e r f o r a t e d with two 6 m m
openings p e r s q u a re foot.
the n u r s e r y .

T h e se p la n ts w e re tr a n s p l a n te d in

At the tim e of a p p licatio n the sun was b r ig h t and

t h e r e w as a high d e g re e of r e f le c te d lig h t f r o m the snow c o v e r
on th e ground.

One m onth l a t e r , th e rm o c o u p le s w e re a tta c h e d

to th e p la n ts un d er p r e v io u s ly applied C h e sle n e a c c o rd in g to
the e x p e r im e n ta l d esig n a s shown in T able 1.

T his was r e p e a te d

on u n c o v e re d p la n ts which w e re im m e d ia te ly c o v e re d in the
sa m e m a n n e r a s b e f o r e , and an add itio n al p a i r of th e rm o c o u p le s
w e re p la c e d a t 2 .5 inch depth in th e so il.

The th e rm o c o u p le s

w e r e a tta c h e d to a ’’M in n eap o lis-H o n ey w ell Brow n e le c tr o n ik "
continuous t e m p e r a t u r e r e c o r d e r .

Daily flu ctu atio n s of t e m p e r -

a t u r e and r e l a t i v e h um idity un der the v a r io u s f o r m s of p o ly ­
ethylene p r o te c tio n f r o m M a r c h 20 to M a r c h 31 was r e c o r d e d
by t h i r t y - h o u r " B e n d i x - F r i e z " h y g r o th e r m o g r a p h s .
One cm s te m s a m p le s w e re c o lle c te d f r o m r a n ­
d o m ized lo c a tio n s on T huja o c c id e n ta lis cv. n ig r a of both
c o v e r e d and u n c o v e re d p la n ts .

They w e re k ille d in f o r m a l in -

a c e tic - a l c o h o l (FAA; 5 cc f o r m a lin , 5 cc g la c ia l a c e tic acid,
and 90 cc 70 p e r cen t ethyl alcohol).

The t i s s u e s w e re d e ­

h y d r a te d u sin g th e t e r t i a r y - b u t y l alcohol s e r i e s , em bedded
in p a ra ffin , sectio n ed t r a n s v e r s e l y 8 m i c r a in th ic k n e s s , and
stain ed with s a f r a n in and a n ilin

blue.

Sections w ere cut f r o m a p p a re n tly u n in ju red
b r a n c h e s of Thuja o c c id e n ta lis cv. n ig r a c o lle c te d on A p ril 10.
The s e g m e n ts u s e d fo r t r e a t m e n t w e r e seven c m f r o m the apex
of th e b r a n c h e s .

O n e -h a lf of the m a t e r i a l w as s to r e d in tap

w a te r and the o th e r half w e re le ft d ry .

T h r e e s te m s of each

of th e s e t r e a t m e n t s w e r e su b jected to the following tim e and
t e m p e r a t u r e s e r i e s (see Table 2).

TABLE

1

The L o c a tio n of T h e rm o c o u p le s at E a c h T r e e Used in the C o u rs e
of T h e se Studies

T h e rm o c o u p le
No.

W here I n s ta lle d on T r e e ,
Type and D ate of C over

P o s itio n in R es
p e c t to T r e e

Middle of p la n t, p e r ­
f o r a te d co v er 2 - 3 - 5 4

South

Apex, p e r f o r a te d c ov er
3 -6-54

South

Apex, n o n - p e r f o r a te d
cover 2-3-54

South

Apex, n o n - p e r f o r a te d
cover 3-6-54

South-we st

M iddle, p e r f o r a te d co v er
3 -6-54

E ast

8

Apex, p e r f o r a te d co v e r
2-3-54

South-we st

9

Apex, not c o v e re d

Tip

10

M iddle, n o n - p e r f o r a te d
cover 3-6-54

We st

11

M iddle, not c o v e re d

N o rth

12

Open so il, 2 1/2 in ch es
Deep

None

14

M iddle, n o n - p e r f o r a te d
cover 2 -3-54

South

16

Soil u n d er T r e e , 2 1/2
in c h es deep

South we st

TABLE

2

T im e and T e m p e r a tu r e T r e a tm e n t, Thuja o c c id e n ta lis cv.
N ig ra S am p les

T r e a tm e n t

Length of T im e of T r e a tm e n t in M inutes
30
60
120
15
A ctu al T e m p e r a tu r e in D e g r e e s F

No w a te r
In w a te r

140. 0
105. 0

140. 0
110 . 0

140. 0
125.6

140. 0
136.4

No w a te r
In w a te r

104. 0
86. 0

104. 0
95. 0

104. 0
100.4

104. 0
107.6

No w a te r
In w a te r

32. 0
50. 0

32. 0
44. 0

32. 0
41. 0

3 2 .0

75. 0

75. 0

75. 0

75. 0

Room t e m p e r ­
a tu re
No w a te r

RESULTS

V acuum T r e a tm e n t of Woody P la n ts :
The a v e r a g e to ta l le n g th of all s te m s of S yringa
v u lg a ris cv. T hu n berg w e re not sig n ifican tly influenced by vacuum
t r e a t m e n t s of w a te r o r in d o le a c e tic acid (Table 3).

G row th of

s te m s was som ew hat inhibited by the w a te r t r e a t m e n t , but m o r e
so by the addition of the in d o le acetic acid (Table 3).
All p lan ts su b jected to a v acu u m i n c r e a s e d the
n u m b e r of s te m s p ro d u c e d f r o m a x illa r y b u d s.

P la n t s t r e a t e d

with w a te r p ro d u ced an a v e r a g e of 12, w h e r e a s those re c e iv in g
in d o lea cetic acid tr e a t m e n t p ro d u c e d 11.2 b r a n c h e s .

T h e re

s e e m e d to be s u p p r e s s io n of grow th of l a t e r a l b r a n c h e s , but
with an in c r e a s e in n u m b e r of b r a n c h e s (Table 3).
F o r s y t h i a sp ectab ilis, on the c o n t r a r y ,

showed a

s u p p r e s s io n in the a v e r a g e lin e a r grow th by t r e a t m e n t with a
vacuum .

Stem elongation in both t r e a t e d groups was sig n ifican tly

l e s s when c o m p a r e d to p la n ts given no v acuu m t r e a t m e n t .

Table

3 shows th a t in d o le a c e tic acid had a decided d e p r e s s in g actio n on
the l i n e a r grow th of l a t e r a l b r a n c h e s .
The a v e r a g e n u m b e r of b r a n c h e s (Table 3) was
lik ew ise l e s s when the p la n ts w ere t r e a t e d with w a te r o r when

35

TABLE

3

L en g th and Amount of Growth as Influenced by V acuum T r e a tm e n t
(40 P la n t s p e r T r e a tm e n t)

U n treated

W ater

In d o lea cetic
Acid

o
•
o
r-H

12. 0

11.2

107.1

98.1

00
*
un
o

43. 6

37. 3

34.1

1545.4

1211. 2

S y rin g a v u lg a ris
A v e ra g e n u m b e r of s te m s
L . S . D . 5%
L . S . D . 1%

1.39
2. 11

A v e ra g e len g th of s te m s (cms)
L . S . D . 5% 2 0 .6
L . S . D . 1% 31.2

F o r s y t h i a s p e c ta b ilis
A v e ra g e n u m b e r of s te m s
L . S . D . 5%
L . S . D . 1%

3 .8
5 .8

A v e ra g e le n g th of s te m s (cms)
L . S . D . 5% 129. 6
L. S .D . 1% 196. 3

1040.6

.

in d o le a c e tic a c id w as added.
In d escen d in g o r d e r ,

sig n ifican tly l e s s b r a n c h e s

w e re p ro d u c e d on p la n ts r e c e iv in g the following tr e a t m e n t s :
u n tr e a te d , w a te r un der vacuum , and in d o leacetic acid under
vacu u m .

Vacuum T r e a t m e n t of L y c o p e rs ic u m :
The to ta l n u m b e r of f r u i t s p ro d u ced by the in d o le ­
a c e tic a c id t r e a t e d c u ltiv a r Red C h e r r y was not sig n ifican tly
d iffe re n t at the 5 p e r cen t le v e l th an the n u m b e r p ro d u ced by the
u n tr e a te d p la n ts .

H ow ever, the in d o leacetic acid t r e a t e d p la n ts

did p ro d u ce a sig n ifican tly g r e a t e r n u m b e r of f r u i t s than those
su b jected to a vacuum t r e a t m e n t of w a te r (Table 4).

The to tal

weight of f r u it p ro d u c e d on te n p la n ts f r o m the w a te r tr e a t m e n t
was sig n ifican tly l e s s th a n e ith e r the u n tr e a te d or the in d o leace tic
acid t r e a t e d p la n ts .

No s ta t i s t i c a l d iffe re n c e s w e re found betw een

the yield of the u n tr e a te d and in d o leacetic acid tr e a t e d p la n ts .
The c u ltiv a r Golden Queen did not re s p o n d to
t r e a t m e n t in the m a n n e r of c u ltiv a r Red C h e r r y .

T h e r e w as no

sig n ifican t d iffe re n c e in the to ta l n u m b e r of f r u it s or the weight
of the f r u i t f r o m t r e a t e d and u n tr e a te d p la n ts .

It m ay be noted

in T able 4 th a t the w a te r t r e a t e d p la n ts p ro d u c e d the lo w est n u m b er

TABLE

4

Yield of F r u i t of L y c o p e r s ic u m e s c u le n tu m c v s . Red C h e r r y and
Golden Q ueen (10 P l a n t s p e r T r e a tm e n t)

U n tre a te d

T r e a tm e n t
W ater Under
V acuum

In d o leacetic Acid
Under Vacuum

N um ber of F r u i t
C u ltiv ar
Red C h e r r y

693

976

1599

1258

1439

155

166

133

918

L . S . D . 5% 2 4 8 .4
L . S . D . 1% 456.1
Golden Queen (Total)
L . S . D . 5% 728.9
L . S . D . 1% 1338.5
Golden Queen (E arly )
L . S . D . 5% 8 9 .4
L . S . D . 1% 164. 1

of f r u it and the l e a s t to ta l weight.
the m o s t to m a to e s .

The u n tre a te d p la n ts pro d u ced

The e a r l y y ield s (total h a r v e s t fo r f i r s t tw o-

week p e rio d ) of a ll t r e a t m e n t s w e re s im i la r in the n u m b e r and to ta l
weight of f r u i t s h a r v e s te d (Table 5).

O b se rv a tio n s in the field i n ­

d ic a te d th a t the n u m b e r of f r u it on each c l u s t e r was g r e a t e r fr o m
the in d o le a c e tic acid t r e a t e d p la n ts .
s t a t i s t i c a l sig n ific a n c e .

This w as not shown to be of

TABLE

5

W eight of F r u i t - L y c o p e r s ic u m e s c u le n tu m c v s. Red C h e r r y
and Golden Queen (10 P la n t s p e r T re a tm e n t)

U n tre a te d

T r e a tm e n t s
W ater Under
V acuum

In d oleacetic Acid
Under Vacuum

Weight of F r u i t (Pounds)
C u ltiv a r
Red C h e r r y

2 2 .6

1 5 .4

23. 3

L . S . D . 5% 6 .3
L . S . D . 1% 11.6
Golden Queen (Total) 793. 9

650. 3

668. 3

9 9 .0

80. 4

L. S .D . 5% 301.1
L . S . D . 1% 5 5 3 .0
Golden Queen (E arly )

9 7 .5

L . S . D . 5% 51. 2
L . S . D . 1% 94. 0

Soaking Woody P l a n t s :
P la n t s of Syringa showed an i n c r e a s e in the a v e ra g e
to ta l li n e a r grow th a s a r e s u l t of a soaking tr e a tm e n t in w a te r.
Those p la n ts whose r o o ts had been soaked gained an a v e ra g e of 9 .2
cm p e r p la n t, but li n e a r grow th was d e p r e s s e d by the addition of
in d o le a c e tic acid to the soaking solution.

The a v e r a g e n u m b e r of l a t e r a l b r a n c h e s p ro d u c ed
on ea c h p la n t w as sig n ifican tly g r e a t e r on the t r e a t e d p la n ts , how ­
e v e r a g r e a t e r n u m b e r was p ro d u c e d on th o s e p la n ts the r o o ts of
which had b e e n soaked in w a te r for two h o u rs (Table 6).

One ppm

/

in d o le a c e tic acid a p p e a re d to d e p r e s s grow th a s m e a s u r e d by the
V

a v e r a g e to ta l len g th of new grow th of F o r s y t h i a .

T h e re was an i n ­

dication th a t soaking the r o o ts of F o r s y t h ia in w ater would i n c r e a s e
the a v e r a g e to ta l len g th of all above ground p a r t s .

V acuum T r e a tm e n t of Annual F lo w e rin g P la n ts :
F r o m T a b le s 7 and 8 it is a p p a re n t th a t th e r e was
little c o n s is te n c y in the grow th of p la n ts sub jected to the v a rio u s
tre a tm e n ts.

Salvia splendens cv. St. J o h n rs F i r e had a g r e a t e r

le a f a r e a on the two sam plin g d a te s .

By the l a te r date, Salvia ,

C a llis te p h u s cv. K irk w ell and C e n t a u r e a , as a r e s u l t of tr e a t m e n t
w ith in d o le a c e tic acid had a g r e a t e r leaf a r e a than the u n tr e a te d
o r the w a te r t r e a t e d p la n ts .
T h e r e w as an i n c r e a s e in the n u m b er of l a t e r a l
b r a n c h e s and le a v e s of Salvia p la n ts which had undergone tr e a t m e n t .
In g e n e r a l, t h e r e w e re v e r y slight d iffe re n c e s in the
n u m b e r of le a v e s p ro d u ced betw een the t r e a t e d and u n tr e a te d p la n ts .
G e n e ra as w ell a s c u l tiv a r s re sp o n d e d d ifferen tly to tr e a tm e n t with
w a te r and in d o le a c e tic a c id .

40.

TABLE

6

Influence of Soaking on G rowth (A verage of 40 P la n t s p e r T re a tm e n t)

U n tre a te d

T r e a tm e n t
Soaked in
W ater

Soaked in In d o le ­
ac e tic A cid

S y rin g a v u lg a r is
A v e ra g e n u m b e r of s te m s

13.4

15.1

14. 3

79.9

89.1

76.1

37. 3

3 8 .4

1170. 0

1008.2

L . S . D . 5% 0 .9
L . S . D . 1% 1.3
A v e ra g e length of s te m s
(cm s)
L . S . D . 5% 7 .2
L . S . D . 1% 10.4
F o r s y t h i a s p e c ta b ilis
A v e ra g e n u m b e r of s te m s 36. 2
L . S . D . 5% 2 .7 0
L . S . D . 1% 3.9 3
A v e ra g e length of s te m s
(cm s)
L . S . D . 5% 5 5 .0
L . S . D . 1% 8 0 .0

1126. 4

TABLE

7

L e a f A r e a (Sq. C m s . ) as Influenced by V acuum T r e a tm e n t s
(2 P la n t s p e r T r e a tm e n t)

Date

F ebruary
17

G e n e ra

T r e a tm e n t
U n tre a te d
W ater

Indo leacetic Acid

Salvia

6036

6796

9444

C a llis te p h u s
cv. Remo

4868

4984

6624

C a lii stephu s
c v .K ir k w e ll 5260

7404

4796

C e n ta u r e a

7040

9074

7352

Salvia

75016

6 9068

87860

C a llis te p h u s
cv. R em o

17588

10592

15388

C a llis te p h u s
c v .K ir k w e ll 16528

19608

22792

C e n ta u r e a

18096

18440

M a rc h

6

15820

co

(2 Plants per

’■d 0
u Xl
o
«! 0
d
Pi
a? PQ
o
d
<U (0
f—I 0
O >

Number of Leaves and Stems as Influenced by Vacuum
T reatment)

Treatments

0

O

CM

vO

O '-

0

sO

t'-

CM
CM

O'

CM
CM

o

vO

CD

0

cd
0
p<
H

x\
o
Pi
Pi d
0 Pi
4->
cd pq
► CD

'vO

0

o

>

nj

co
r-

0

CD

0

rd
u

ro

Pi
CCJ

T3 U
0 «
+J
rd
0 CD
Pi 0
+->
>
Pi c
cJ

oo

00

oo

to

CM

vO

0

CD

r>

CD

°

a, S

0

0

0

rd

0

o

CD

0

£

5
t;

« ft

r—4

d
CO

0

co
d
xi
ft
0

o

0

Pi

0

d
nj >
O u

0 O
nQj sP>

C
C
S

Pi
0

U

rt

• iH
>
»—H

d

m

Pi
cd

0

Pi

X0>
U*

xi
o
So

+-> pi
CD

•H
r-H
i— <

cd

O

^
_
l

>
u

CD

3 '—0I

M *
Pin M
0
Pi
+-* • rH

.2
W
i—I
•
rl™ u
>
U

cd

0

Pi

0

d

+ ->

Pi
0

U

P o ly e th y le n e C o v erin g on Thuja o cc id e n ta lis :
A ir t e m p e r a t u r e a s well a s t e m p e r a t u r e s at v a r io u s
lo c a tio n s on p la n ts of Thuja o c c id e n ta lis cv. n i g r a flu ctu ated
widely d u rin g a 2 5 -d ay p e r io d in M a rc h 1954.

T e m p e r a t u r e s on

u n p ro te c te d p la n ts w e r e c o n s is te n tly lo w er than e x istin g o ffi­
c ia l t e m p e r a t u r e s r e c o r d e d by the W eather B u re a u in the sam e
v ic in ity .

T e m p e r a t u r e s of p la n ts c o v e re d with nC h e s le n e n p ro ­

te ctio n w e re h ig h e r .

The t e m p e r a t u r e s un d er p e r f o r a t e d film

w ere slig h tly lo w e r (1 to 3°F) th an under n o n - p e r f o r a te d c o v e r .
The h ig h e st t e m p e r a t u r e s w e re o b s e r v e d betw een 1200 and 1500
h o u rs , and th e lo w e st t e m p e r a t u r e s w ere at 0600 h o u r s .

The

o
m a x im u m soil t e m p e r a t u r e was 50 F with d iu rn a l flu ctu atio n s
of a p p r o x im a te ly 2 8 ° F .
F o r 17 days d urin g the e x p e rim e n t snow w as on the
g round.

T o tal su n sh in e d u rin g the m onth of M a r c h was 204 h o u r s ,

only 55 p e r cen t of the m a x im u m .
D e s ic c a tio n and brow ning was p r e v a le n t on all
c o v e r e d t r e e s , which w as m o r e in ten se on the south and s o u th ­
w e st e x p o s u re and c o n c e n tr a te d at the apex.

This in ju ry did not

alw ays o r ig in a te at the ap ex of the b ra n c h , nor was in ju ry lim ite d
to p o in ts of c o n tact betw een b r a n c h e s and the p la s t ic .

In ju ry was

of two ty p e s (a) d e s ic c a tio n and browning of the le a v e s and b ra n c h e

and (b) d e s ic c a tio n w ithout the acco m p an y ing brow ning.
D e s ic c a tio n o c c u r r e d f i r s t on the ex po sed side of
the b r a n c h , and g ra d u a lly affe c te d the e n tir e b r a n c h .
s ta g e s , the b r a n c h was b r i t t l e .

At l a t e r

F re q u e n tly , d e s ic c a tio n was

evident and bro w n in g did not develop.
R elativ e h um idity flu ctu ated betw een 100 p e r cent
d u rin g the p e r io d s of lo w est te m p e r a t u r e , f re q u e n tly d e c r e a s in g
to 20 p e r cen t d u rin g p e r io d s of h ig h e r t e m p e r a t u r e s .

E vapor­

ation w as r e d u c e d by the polyethylene c o v e r b e c a u se of low
m o i s t u r e m o v e m e n t c a p a c ity of the film , and the r e d u c e d a i r
m o v e m e n t w ithin the e n c lo s u r e .

W ater fre q u e n tly co n d en sed

in the fo ld s of the p la s tic with a lo w erin g of the t e m p e r a t u r e .
T e m p e r a t u r e - r e l a t i v e hum idity r e la tio n s h ip s
of a i r , u n d er n o n - p e r f o r a te d and under p e r f o r a te d t r a n s p a r e n t
p o lyethylene a r e shown in F i g u r e s 1, 2 and 3.
The p la s tic film w as su b ject to r a p id b reakdow n
by sp littin g u n d e r fie ld conditions during M a rc h 1954.

45.

80

0 0

70

60

60

Humidity

in Per

-

Cent

80

Relative

50 -

40

30
1800

-20

2400

0600

1200

T im e in H ours

F i g u r e 1. T e m p e r a tu r e and r e la tiv e hum idity of open a i r
o v er r e p r e s e n t a t i v e 24 hour p e rio d .

180

46.

100

70

80

60H

60

CO

cu

Temperature

in Degr

0

40 H

30-

20H
(800

2400

0600
Tim e In Hours

1200

F ig u r e 2. F o u r day a v e ra g e of te m p e r a tu r e and
r e la tiv e hum idity for a ir en clo sed in a p e r f o r a te d
polyethylene c o v e r.

1800

(.

100

70

Relative

Temperature

Humidity

in Degrees

40

in Per

Cent

60

3oH

20 H

800

2400

0600

1200

Tim e in Hours

F ig u r e 3. F o u r day a v e ra g e of t e m p e r a t u r e and r e la tiv e
hu m id ity fo r a ir en clo sed in n o n - p e r f o r a te d p o ly ­
ethylene c o v e r .

1800

T r a n v e r s e s e c tio n s of six p a i r s of s c a le - lik e
le a v e s w e r e i l l u s t r a t i v e of the d e c u s s a te phyllotaxy of Thuja
o c c id e n ta lis cv. n i g r a (Figure 4).

The c e n t r a l c y lin d e r was

in e a r l y s ta g e s of unlignified, but th ick en ed p r i m a r y x y le m
d if f e r e n tia tio n .

M o st of the c e lls w e re i r r e g u l a r p a re n c h y m a

with d en se c y to p la s m and p r o m in e n t'n u c le i.
The individual le a v e s w e re p r o te c te d by a heavy
som ew hat scallo p ed c u tic u la r c o v e rin g on the ab ax ial s u rfa c e
( F ig u re 5).

F r e q u e n t d e p o sits of unidentified m a t e r i a l s a p ­

p e a r e d to be b u r ie d in the c u tic le .

T his cu ticle was a p p r o x ­

im a te ly tw ice the depth of the subtending e p id e r m is , to which
it a p p e a r e d to be co n n ected by p la s m a d e s m a t a .
The e p i d e r m is c o n s is te d of a single row of ta n g en tially elongated c e lls , with s p in e -lik e p ro je c tio n s on the
a b a x ia l s u r f a c e .

The w alls of the e p id e r m is w e re of c e llu lo sic

co m p o sitio n , th ick , with conspicuous c y to p la s m and n u c le i.
S to m ata w e re not f r e q u e n t in th e i r d is tr ib u tio n o v er the s u r f a c e .
D ir e c tly b e n e a th the e p id e r m is was a single or
double l a y e r e d h y p o d e rm is co m posed of co llen ch y m a c e lls which
w e re polygonal in t r a n s v e r s e sectio n .

The cell w alls w e re e x ­

t r e m e l y th ic k , p e n e t r a te d by sim p le p its and contained v e ry s m a ll
lu m e n .

F i g u r e 4. T r a n s v e r s e s e c tio n of ste m and le a v e s of
Thuja o c c id e n ta lis cv. n ig r a , one cm f r o m the apex
(X80).

F ig u r e 5. T r a n s v e r s e sectio n of one co m p lete le a f of
Thuja o c c id e n ta lis cv. n ig r a , one cm fr o m the apex
of the s te m (X240).

A single la y e r of elo n g ated p a l is a d e - li k e p a r e n ­
ch y m a c e l ls w as lo c a te d b e n e a th the h y p o d e r m is .

T h ese c e l ls

w e re i r r e g u l a r in s iz e and a r r a n g e m e n t, and co ntained dense
c y to p la s m with l a r g e p r o m in e n t n u c le i.

S u rrounding the s p e c i a l ­

iz ed t i s s u e s w e re i r r e g u l a r l y shaped p a re n c h y m a c e l l s , l o o s e ­
ly a tta c h e d with la r g e i n t e r c e l l u l a r a i r s p a c e s .

C onspicuous

d ep o s its of ta n n in w e re found in the p a re n c h y m a to u s m a s s of
tissu e .
The vein was su rro u n d e d by a la y e r of h eav y w alled e n d o d e rm a l c e l ls which w ere som ew hat i r r e g u l a r in
shape and u su ally r a d ia lly fla tte n e d .

Surrounding the ad ax ial

x y le m and ab a x ia l p hlo em w e re i r r e g u l a r l y shaped p a r e n c h y ­
m a to u s and tr a c h e i d c e l ls t e r m e d tr a n s f u s io n t i s s u e .
A djacen t to the adaxial e p id e r m is was a single
la y e r of ta n g e n tia lly elongated p a re n c h y m a .

The e p id e r m is

a d ja c e n t to the c e n t r a lly lo c a te d s te m was co m p o sed of la r g e
c e lls with convex o u te r w a lls, often in te r r u p te d by sunken
s to m a ta ( F ig u re 6) with th e ir s u b s id ia ry c e lls arc h in g ov er
the g u a rd c e l l s .

A p o rtio n of the g u ard c e ll w alls w ere lig n i-

fied and p a r t l y c e llu lo s ic .

T his e p id e r m is is c o v e re d by a

thin la y e r of c u tic le , except o v er the s u b s id ia ry c e l ls w h ere

52,

h e a v i e r d e p o s its w e r e found.
A djace n t to the a b ax ial s u r f a c e of m a t u r e

le a v e s one

o r m o r e r e s i n ducts w e re found, which w e re lin ed by elongated
e p ith e lia l c e l l s ( F ig u r e s 7 and 8).
In o ld e r s te m s , the pith c e lls w e re su rro u n d e d
by e x tr e m e ly heavy c e llu lo s e w alls (F ig u re 9).

The r a y c e lls

of the x y le m w e r e g r e a t ly elongated to w a rd the p e r ip h e r y of
the s te m .

They w e re p a re n c h y m a to u s , a r r a n g e d in a u n is e r i a te

row , b e co m in g m o r e t e a r - d r o p shaped c e lls in the phloem
re g io n .

The c a m b ia l zone s e p a r a te d the x ylem c y lin d e r and

the p h lo e m , which was co m p o sed of a lte r n a tin g l a y e r s of
sieve c e l ls , f u s if o r m and s to r a g e p a re n c h y m a .

The p r i m a r y

phlo em and c o r te x w e re an in d istin g u ish ab le c r u s h e d m a s s .
N a tu ra lly o c c u r r i n g in ju ry on Thuja o ccid e n ta lis
cv„ n ig r a , although difficult to identify, g e n e ra lly m a n ife s te d
it s e l f as a lo s s of the d a r k g re e n c o lo r c h a r a c t e r i s t i c of the
c u l tiv a r .

On the p a r t s ex p o sed to the continuous so u th -w e s t

winds, th is p lant b e c a m e r e d d is h - o liv e g r e e n n e a r the a p ic e s
of the b r a n c h e s .

This condition was difficult to d istin g u ish

f r o m in ju ry which was u s u a lly t e r m e d w in ter in ju ry , b e c a u se
the c o lo r was b e lie v e d to be a n a tu ra lly o ccu rin g phenom enon

g u r e 6. T r a n s v e r s e s e c t i o n of o u t e r l a y e r s of c e l l s of
l e a f of T h uj a o c c i d e n t a l i s cv. n i g r a showing the
c u t i c l e A, s t o m a B, s u b s i d i a r y c e l l s C, g u a r d c e l l D,
and a d j a c e n t m e s o p h y l l E (X100Q),

F i g u r e 7. T r a n s v e r s e s e c t i o n of t h r e e l e a v e s and s t e m s of
T h u j a o c c i d e n t a l i s cv. n i g r a six c m s f r o m the apex
show ing a l a r g e r e s i n duct in the m e s o p h y l l (X8Q).

55.

F i g u r e 8. T r a n s v e r s e s e c t i o n of a l e a f of Thu ja o c c i d e n t a l i s
cv. n i g r a s ix c m s f r o m the a p e x showing a l a r g e r e s i n duct
in the m e s o p h y l l {X240).

F i g u r e 9. T r a n s v e r s e s e c t i o n of m a t u r e l e a v e s and s t e m
of T h u j a o c c i d e n t a l i s cv. n i g r a six c m s f r o m apex
(X80K

57.

of th e g en u s.

I n ju ry a p p e a r e d to o r ig in a te on the south to

s o u th - w e s t e x p o s u r e of the t r e e .

T h is type of in ju r y is i l l u s ­

t r a t e d in th e acc o m p a n y in g p h o to m ic r o g r a p h ( F ig u re 10).
The m o s t c o n s p ic u o u s d is c e r n i b le m o d ific a tio n
of th e le a f w as the in a c tiv a tio n of the ab a x ia l e p id e r m a l c e l l s ,
b ro u g h t about by the d e p o s itio n of a m u c ila g e .
som ew hat p la s m o ly z e d .

F ew c e lls w ere

E p i d e r m a l and h y p o d e rm a l c e l ls c o n ­

ta in ed lu m e n p ack ed with ta n n in - lik e d e p o s its .

T h e se c e lls

w e re s h ru n k e n , le a v in g l a r g e i n t e r c e l l u l a r s p a c e s .
P a l i s a d e - l i k e c e l ls w e re found to be sh ru n k en in
d iffe re n t p a t t e r n s ( F ig u re 11).

In g e n e r a l, the w alls of the

lo n g e st d im e n s io n b e c a m e con cav e, acco m p an ied by a s h r i n k ­
age of the p r o to p l a s m (F ig u re 12).
p r e v a l e n t and r e la tiv e l y l a r g e .

I n te r c e llu l a r s p a c e s w e re

C ells of m e so p h y ll w e re i r ­

r e g u la r ly a r r a n g e d , with the v a ry in g conditions of p r o to p la s m
s h rin k a g e being of p a r a m o u n t i n t e r e s t .

In some c a s e s the

c y to p la s m a p p e a r e d to be a lm o s t c o m p lete ly a b se n t.

The ph loem

e le m e n ts of the v a s c u la r s tr a n d w ere i r r e g u l a r in shape and
condition.

The c y to p la s m was e x tre m e ly d en se, and some c e lls

a p p e a re d p h y sio lo g ic a lly in a c tiv e .
The x y le m c e l ls s e e m e d to be little affected .

The

F i g u r e 10. T r a n s v e r s e s e c t i o n of p a r t of l e a f and s t e m of
T h u j a o c c i d e n t a l i s cv. n i g r a t e n c m s f r o m the apex
s h ow ing t h e i n j u r y d ev e lo p in g on the o u t e r edge of the
e x p o s e d l e a f (X80).

F i g u r e 11. T r a n s v e r s e s e c t i o n of a l e a f and p a r t of a s t e m of
T hu ja o c c i d e n t a l i s cv. n i g r a eight c m s f r o m the apex
showing i n i t i a l s t a g e s of d e h y d r a t i o n on p l a n t s in the open
f ie l d (X80).

F i g u r e 12. T r a n s v e r s e s e c t i o n of p a r t of l e a f of T h u ja o c c i d e n t a l i s
cv. n i g r a e ig h t c m s f r o m the ap ex showing i n it i a l s t a g e s of
d e h y d r a t i o n on p l a n t s in the open fie ld (X240).

61.

t r a n s f u s i o n t i s s u e s u rro u n d in g the v a s c u la r s tr a n d was
c o lla p s e d , giving the a p p e a ra n c e of r a d ia l s tr e tc h in g .

Slight

m o d ific a tio n s of the e n d o d e r m a l c e lls w e re p r in c ip a lly wrought
by s h r in k a g e s of the c y to p la s m and the c e ll w alls to a l e s s e r
ex ten t.
The a d ax ial e p id e r m a l c e l ls a p p e a re d to be fu n c ­
tio n a l, but with m in o r d e p o s itio n s of the tannin m a t e r i a l s .
c e lls w e r e so m ew hat f la tte n e d .

The

No ru p tu r in g of cell w alls was

o b s e rv e d in any of the p r e p a r a t i o n s .

The cu ticle r e m a in e d

thick, and unchanged.
In ju ry to the le a v e s of p la n ts c o v e re d with p e r ­
f o r a te d and n o n - p e r f o r a te d polyethylene was in the fo r m of
ch lo ro p h y ll d e s tr u c t io n .
and fin ally b ro w n .

The le a f was f i r s t pale g re en , yellow

The c h lo ro p la s ts of the le a v e s of Thuja

o c c id e n ta lis cv. n ig r a w ere d is tr ib u te d in the p a re n c h y m a of
the m e s o p h y ll.
w e re a tro p h ie d .

C e llu la r contents of the abaxial e p id e r m is
D ense tan n in m a t e r i a l s filled the lu m en s of

m o s t of the e p id e r m a l and collen ch y m a c e l l s .

All c e lls of

the m e so p h y ll la y e r w e re c o n tra c te d , with a g r e a t e r d eg ree
o£ p l a s m o l y s i s and p r e s e n c e of deposition p ro d u c ts within the
c e ll.

S e v e re in ju ry which u ltim a te ly c a u s e d the death
of the p la n t p ro d u c e d e x t r e m e atro p h y of the e p id e r m a l c e l ls ,
the ab a x ia l s u r f a c e of which w as p ro n ouncedly convex (F ig u re
13).

C o n ten ts of a ll c e l ls w e re e x tr e m e ly re d u c e d in a r e a ,

with a m a r k e d d e r a n g e m e n t of the c e l l s .

R upturing of c e ll

w alls was ex ceed in g ly r a r e , even at the p ro to p la s m ic death
p o in t.

In th e s te m , a ll p a re n c h y m a to u s c e lls , r e g a r d l e s s

of lo c a tio n , w e r e sh ru n k en , contained d ep o s its of ta n n in s, and
w e re d e fo rm e d .
c o n s e q u e n tia l.

In ju ry to the x y le m c e lls and f ib e r s was not
P a r e n c h y m a in the p ith re g io n was a lso affected

but u s u a lly without r u p tu r in g of the cell w alls.
In le a f and s te m p a r t s of Thuja o c c id e n ta lis cv.
n ig r a , w hich had b een a r ti f ic a l ly fro zen , the cu ticle , e p id e r m is
and h y p o d e rm is w ere not o b s e rv e d to d iffer fro m u n inju red
t i s s u e s (F ig u r e 14).

The lo c atio n of the p a re n c h y m a c e lls of

the m e so p h y ll w as g r e a tly a l t e r e d by fre e z in g .

Although

som e p la s m o ly s is a p p e a re d , the p r in c ip a l in ju ry was the r u p ­
t u r e of the c e ll w alls of m any c e lls , both in the le a v e s and in
the s te m .

E x te n siv e r u p tu rin g o c c u r r e d at the union of pith

and p r i m a r y x y le m , in som e c a s e s following the xylem ra y
to w a rd the p e r ip h e r y of the s te m .
what s e p a r a t e d .

X ylem c e lls w ere s o m e ­

F i g u r e 13. T r a n s v e r s e s e c t i o n of a m a t u r e s t e m and l e a v e s of
T h u j a o c c i d e n t a l i s cv. n i g r a t e n c m s f r o m a p e x showing
s e r i o u s d e h y d r a t i o n of t i s s u e a t 150°F (X80).

64.

F i g u r e 14. T r a n s v e r s e s e c t i o n of s t e m and l e a v e s of Th uja
o c c i d e n t a l i s cv. n i g r a s e v e n c m s f r o m the a pex showing
i n j u r y f r o m f r e e z i n g at 32 F (X80).

A r tif ic a lly induced d e s ic c a tio n by high t e m p e r a ­
t u r e s s e v e r e l y a l t e r e d the c e l lu la r an ato m y of the le a f and
s te m of Thuja o c c id e n ta lis cv. n i g r a (F ig u r e 15).

The ab a x ia l

e p id e r m a l c e l ls b e c a m e d e p o s ito r ie s f o r ta n n in s u b s ta n c e s .
The c e l ls w e re a tro p h ie d ,
convex.

sh ru n k en , and a b a x ia l w alls w e re

The h y p o d e rm a l c e ll lu m en w e re p ac k e d with

ta n n in - lik e d e p o s its ( F ig u r e 16).
M is s h a p e n m e so p h y ll w as i r r e g u l a r , often
filled with ta n n in m a t e r i a l s and p la s m o ly z e d in v a r io u s d e g r e e s .
R upturing of th e p a re n c h y m a c e l ls s o m e t im e s o c c u r r e d .

The

c e lls of the a d a x ia l e p i d e r m is w e re not a s fre q u e n tly p la s m o ly z e d
although t h e r e s e e m e d to be som e ta n g e n tia l s h rin k a g e .

Some

c e lls a p p e a re d a lm o s t globose, with the convex s u r f a c e to w a rd
the p e r i p h e r y .
P a r e n c h y m a c e lls of the phlo em a s well a s the
xylem r a y s w e re p a r tl y shrunken, and often d e p o s ito r ie s fo r
the ta n n in s u b s ta n c e s .

F i g u r e 15. T r a n s v e r s e s e c t i o n of l e a v e s and s t e m of T h uja
o c c i d e n t a l i s c v . n i g r a 10 c m s f r o m the a p e x of the s t e m
—■—
1
o
showing i n j u r y f r o m d e h y d r a t i o n a t 140 F in an oven (X80).

F i g u r e 16. T r a n s v e r s e s e c t i o n of l e a v e s and s t e m of T huja
o c c i d e n t a l i s cv. n i g r a 10 c m s f r o m apeg: of the s t e m
showing i n j u r y f r o m d e h y d r a t i o n at 140 F in an oven (X240).

DISCUSSION OF R E S U L T S

F r o m the r e s u l t s of the e x p e r im e n ts a tte m p tin g
to im p ro v e gro w th following tr a n s p la n tin g , it was not p o s s ib le
to m a k e d efinite c o n c lu s io n s .

No one m eth o d o r one c o n c e n ­

t r a t i o n was co m p le te ly s u p e r i o r .
The v acu u m m eth o d of a p p licatio n of growth r e g u ­
l a t o r s could be added to an a lre a d y expanded l i s t of techniques
of ap p licatio n :

Cholodny, 1936; H a r r is o n , 1937; Block, 1938;

R o m b e rg and Sm ith, 1938; S tie r and duBuy, 1938; Thim ann and
L an e , 1938; Howlett, 1939; G ustafson, 1940; Sw artley, 1941;
Z i m m e r m a n and H itchcock, 1944; Withrow, 1945; F e l b e r , 1947;
W atson, 1948; Randhaw a and Thom pson, 1948; M itchell, 1951;
D o ran , 1952; Nagato and Sato, 1952; and A se n and H am n er,
1953.
In g e n e r a l , to ta l lin e a r growth was r e t a r d e d by
the u se of one ppm in d o le a c e tic acid solution.

P e r h a p s the

grow th r e g u la to r r e t a r d e d the te r m i n a l p o rtio n of the ste m , and
co n seq u en tly s tim u la te d the grow th of a x illa r y b u ds.

Support

of th is r e a s o n in g was o ffere d by Z im m e r m a n and H itchcock (1940,
1942) u sin g h o rm o n e t r e a t e d H ib iscu s s y r i a c u s ;and R o sa h y b rid a
cv. B e t te r T i m e s , A sen and H a m n e r (1953).

P r e c i p i t a t i o n May to N o v e m b e r, 1953 C o m p a re d to th e 3 0 - Y ear
A v e ra g e *
P r e c ip ita tio n (Inc he s )
Month
A v e ra g e

X953.

3 .7 5

1.75

Jdne

3. 37

2 .8 7

. July-

2 .2 8

1, 03

A ugust

2. 68

3 .8 0

S e p te m b e r

3. 05

1.40

O c to b e r

2 ,4 5

1.43

■

F r o m U. S. W e a th e r B u r e a u lo c a l c lim a to lo g ic a l d a ta .

70

In t h e s e e x p e r im e n ts and as pointed out by G o s s a rd
in 1943, t h e r e w e r e , c o n t r a r y to the findings of S w artley (1941)
and G r e g o ry , Im le and C am acho (1953), v e r y few d iffe re n c e s in
th e p e r cen t s u r v iv a l of the tr a n s p l a n te d p la n ts .
The low c o n c e n tra tio n of indole ace tic acid m a y have
s tim u la te d the m e r i s t e m a t i c r e g io n s , p a r t i c u l a r l y in the a p ic a l
buds r e s u l t i n g in ra p id and pro lo n g ed a c tiv ity .

In 1925, Snow

d e m o n s t r a te d th a t P h a s e o lu s v u lg a r is exhibited a p o sitiv e c o r r e ­
la tio n b etw een the am ount of grow th s u b sta n c e s applied and the
a c tiv ity of the c a m b ia .
Since the p la n ts r e c e iv e d no s u p p le m e n ta ry i r r i ­
gation d u rin g the p e r io d f r o m May to N o v em b er, the grow th m ay
have b e e n r e d u c e d by a deficiency of w a te r, a s th e r e was l e s s
p r e c i p ita t io n in 1953 than the th ir ty y e a r a v e ra g e (Table 9).
In add itio n to the d iffe re n t am ounts of li n e a r growth
obtained fo r woody p la n ts , a s a r e s u l t of t r e a t m e n t p r i o r to t r a n s ­
p lan tin g , y ie ld s of L y c o p e r s ic u m e sc u le n tu m d iffered in n u m b e r and
weight of f r u i t (T ab les 4, 5).

In c o n t r a s t to the findings of S tier and

duBuy (1938), no sig n ifican t d iffe re n c e s w ere shown fo r the c u ltiv a r
Golden Q ueen e ith e r in n u m b e r o r weight of e a r ly or to tal p ro d u ctio n .
R e s u lts of Z i m m e r m a n et al (1944) and W ithrow (1945), how ever,

w e r e in c o m p le te a g r e e m e n t with the r e s u l t s r e p o r te d at
th is t i m e .
The c u ltiv a r Red C h e r r y exhibited no significant
d if f e r e n c e s in yield b etw een the u n tr e a te d and in d o leacetic
a c id t r e a t e d p la n ts .

W ater t r e a t e d p la n ts p ro d u ce d s ig n ifi­

can tly l e s s f r u i t th a n the in d o leac etic acid, but not the u n ­
tre a te d p la n ts.

In w eight, the w ater t r e a t e d p la n ts p ro d u ced

l e s s f r u i t th a n e ith e r the u n tr e a te d o r in d o leac etic acid tr e a te d
p la n ts .
Annual flo w erin g p la n ts exhibited a v a r ie ty of
r e s p o n s e s (T ab les 7 and 8).

Im m e d ia te ly following tr e a tm e n t ,

s te m s bent and th is p e r s i s t e d fo r a s h o rt p e r io d of tim e .
M itc h e ll (1938) had o b s e rv e d th is phenom ena in P h a s e o lu s ,
T a g e te s , and C o le u s.

A delay of flow ering of Salvia splendens

o c c u r r e d a s a r e s u l t of the in d o leacetic acid inhibition of the
t e r m i n a l grow th, s tim u la tin g the a x illa r y b r a n c h e s which
w e re p r e v e n te d f r o m d iffe re n tia tio n of f lo r a l p r im o r d ia ,
L o s s of the s m a l l e r buds as a r e s u l t of the use of grow th
r e g u l a t o r s w as r e p o r t e d by Z i m m e r m a n and Hitchcock (1944).
The d e h y d ra tio n of le a v e s on u n p ro tec ted p lan ts
h a s b e e n a t tr ib u te d to high, r a t h e r than low t e m p e r a t u r e .

The

d is tin g u is h in g c h a r a c t e r i s t i c s of the in j u r ie s r e s u ltin g f r o m
a r a n g e of t e m p e r a t u r e w ere th a t (a) at high t e m p e r a t u r e s , even
fo r s h o r t p e r i o d s , d e s ic c a tio n of the t i s s u e s r e s u lt e d in a
sh rin k a g e of the c e l ls of the e p i d e r m is , m eso p hy 11 and t r a n s ­
fu s io n t i s s u e s ; and (b) at low t e m p e r a t u r e s , ru p tu r in g and
s e p a r a t in g of the c e l ls o c c u r r e d , p a r t i c u l a r l y th o se of
p a r enc h y m a .
The r a t e of w a te r l o s s f r o m a plan t h as been
c a lc u la te d co m m on ly by the d e te r m in a tio n of v apo r p r e s s u r e
d e f ic its a s w as done by C o stin g in 1950.

V apor p r e s s u r e

d e fic it ca n be ex p lain ed a s the d iffe re n c e betw een the am ount
of w a te r v ap o r a c tu a lly p r e s e n t , and the am ount th at could
e x i s t w ithout c o n d en satio n when the te m p e r a t u r e s of the a i r
and e v a p o ra tin g s u r f a c e w e r e equal (T hornthw aite, 1940).
Since th is m ig h t be c o n s id e r e d to be a d ir e c t in d icatio n of
a tm o s p h e r ic m o i s t u r e , independent of the t e m p e r a t u r e , it was
b e lie v e d to be m u c h m o r e in d icativ e of the po ten tial r a t e of
e v a p o r a tio n .

By u sin g ta b le s of v ap o r p r e s s u r e s (Table 10),

it w as p o s s ib le to t r a n s f o r m r e la tiv e h u m id itie s to vapor
p r e s s u r e d e fic its f r o m the known t e m p e r a t u r e .

By e r e c tin g

a c h e e s e c lo th e n c lo s u r e , B atso n (1933) was able to in c r e a s e

th e r e l a t i v e hu m id ity su rro u n d in g the p lan t by the cooling
effect of shade and r e s u lt in g r e d u c tio n in r a t e and am ount
of t r a n s p i r a t i o n .
F r o m F i g u r e s 1, 2 and 3, the in v e r s e r e l a ­
tio n sh ip of t e m p e r a t u r e and r e la tiv e hum idity is a p p a re n t.
The tim e of i n t e r s e c t i o n was 1 to 2 h o u r s e a r l i e r when
r e c o r d i n g s w e re obtained e ith e r u n d er n o n - p e r f o r a te d o r
p e r f o r a t e d poly eth y lene film .

T h is was b eliev ed to have

b e e n c a u s e d by the s o la r ra d ia tio n and the r e t a r d e d m o v e ­
m e n t of the a i r e n c lo se d with the p lan t.

F r o m Table 10

u sin g the t e m p e r a t u r e s and r e la tiv e h u m id itie s , the vapor
p r e s s u r e d e fic it w as d e te r m in e d .

F o r the a i r the m a x im u m

v a p o r p r e s s u r e d eficit was 9. 5, and fo r the p e r f o r a te d p o ly ­
eth y len e a p p r o x im a te ly 3 3 .7 m m of m e r c u r y .

T his deficit

b ein g g r e a t e r , c a u s e d a m ov e m en t of w ater f r o m the p la n t.
The r a t e of diffusion th ro u g h th e s to m a ta was g r e a t e r at
h ig h e r t e m p e r a t u r e s .
T a b le s 11, 12, 13, and 14 show the t e m p e r a t u r e s
of (a) open a i r , (b) s o i l - -2 1/2 inch depth, (c) a i r u n d er n o n ­
p e r f o r a t e d , and (d) a i r u n d er p e r f o r a te d polyethylene c o v e r s .
The soil t e m p e r a t u r e flu c tu a te d to a l e s s e r d eg ree than

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T A B LE

11

© pen A i r T e m p e r a t u r e s At C ottage G a rd e n s N u r s e r y , E a s t
L a n s in g , M ich ig an fo r 25 D ays of M a r c h 1954.
Day

High

Low

M ean

1

29
3$
34
40
34
41
26
40
29
32
39
42
49
41
28
31
35
47
43
65
33
42
48
17
23

22
18
17
25
23
19
17
20
12
10
15
18
18
30
17
13
11
23
18
32
17
16
19
0
0

2 5 .5
2 7 .0
2 5 .5
3 2 .5
2 8 .5
3 0 .0
2 1 .5
30. 0
2 0 .5
2 1 .0
2 7 .0
30. 0
33. 5
3 5 .5
2 2 .5
2 2 .0
2 3 .0
3 5 .0
3 0 .5
4 8 .5
2 5 .0
2 9 .0
3 3 .5
8 .5
1 1 .5

5

10

15

20

25

76.

TA BLE

12

Soil T e m p e r a t u r e at 2 1/2 Inch Depth for 25 Days of M a rc h 1954

Day
1

5

10

15

20

25

High
29
30
35
35
42
51
28
30
27
34
40
44
49
37
32
29
30
47
40
55
36
46
50
28

Low
25
24
25
27
27
27
25
26
24
22
23
25
25
27
26
21
23
25
25
31
22
23
20
24

M ean
2 7 .0
2 7 .0
30. 0
31. 0
34. 5
3 9 .0
26. 5
28. 0
2 5 .5
28. 0
3 1 .5
34. 5
37. 0
32. 0
2 9 .0
25. 0
26. 5
36. 0
3 2 .5
43. 0
2 9 .0
2 9 .5
35. 0
26. 0

77.

TABLE

13

A fr T e m p e r a t u r e U nder N o n - p e r f o r a te d T r a n s p a r e n t P o ly eth y le n e
C o v e r f o r 25 B ay s of M a r c h 1954
Bay
1

5

10

15

20

25

High
125
124
119
119
116
112
45
94
94
116
115
103
119
48
63
112
100
75
82
76
58
96
80
35
137

Low

M ean

17
11
10
14
12
11
10
20
13
2
7
8
12
27
15
5
3
20
14
32
8
10
19
0
0

7 1 .0
6 7 .5
64. 5
66. 5
6 4 .0
6 1 .5
27. 5
57 .0
53 . 5
5 9 .0
6 1 .0
5 5 .5
65. 5
3 7 .5
3 9 .0
58.5
5 1 .5
4 7 .5
4 8 .0
5 4 .0
3 3 .0
53. 0
4 9 .5
17.5
68. 5

78

TABLE

14

A i r T e m p e r a t u r e U nder P e r f o r a t e d T r a n s p a r e n t P o ly eth y len e
C © y e r f o r 2 5 D a y s o f M a r c h 1954

Day
-.^ -1

.i -'j ;

~ u .f' j

,i

High
.

■ ii i ij

.n ; » ,-i ' .

.1.'.

’

jr

, .....I, . i .

105
116
106
103
105
105
51
80
83
102
98
87
96
47
51
93
75
64
72
71
34
59
50
17
41

Low
.

, Li.

i

15
13
11
13
14
10
12
20
13
3
9
9
15
27
10
4
3
19
12
31
17
16
19
0
0

L.-j ..ji

M ean
' , , 11.

'

6 0 .0
6 4 .5
58 . 5
591 0
5 9 .5
37. 5
31.5
50. 0
4 8 .0
52. 5
53.5
4 8 .0
55.5
37 .0
30 .5
4 8 .5
3 9 .0
4 1 .5
4 2 .0
51. 0
25. 5
37. 5
3 4 .5
8 .5
2 0 .5

a t m o s p h e r ic t e m p e r a t u r e s .

The m e a n t e m p e r a t u r e s under

th e p o ly e th y le n e c o v e r s w e re c o n s is te n tly m uch w a r m e r than
in th e open a i r .

T e m p e r a t u r e s u n d er the t r a n s p a r e n t p o ly ­

eth y len e c o v e r s of o v e r 100°F w e re not uncom m on on b rig h t
c le a r days.
The soil t e m p e r a t u r e s d u rin g the p e r io d of i n ­
j u r y w e r e r a r e l y m u c h above f r e e z in g .

K r a m e r (1940) c o n ­

clud ed th a t th e p h y sio lo g ical a c tiv itie s of r o o ts w e re g re a tly
r e d u c e d by d e c r e a s i n g t e m p e r a t u r e s , e s p e c ia lly the a b s o r p ­
tio n of w a t e r .

F r o m the d a ta of R o e s e r (1932), it w as found

th a t c e r t a i n e v e r g r e e n s lo s t c o n s id e ra b ly m o r e w a te r by
t r a n s p i r a t i o n at a t e m p e r a t u r e of 51°C than at 16°C.
The r e la tiv e l y low t e m p e r a t u r e s of the soil probably
p re v e n te d the a b s o r p tio n of w ater by the p la n t in sufficient
q u a n titie s and ra p id ly enough to r e p la c e th a t lo s t by t r a n s ­
p ir a t io n .
It is b e lie v e d th a t low t e m p e r a t u r e s of the soil,
high a i r t e m p e r a t u r e s , and high vap o r p r e s s u r e d e fic its a c ­
counted fo r the d e s ic c a tio n in ju ry to the plant.

T his w as, in

g e n e r a l a g r e e m e n t w ith the findings of B r ie r l e y and Landon
(1946) and M axim ov (1929).

80.

M ic r o s c o p ic v a r ia tio n s in the type of in ju ry p r e ­
se n te d showed s h rin k a g e and d ep o sitio n s r e s u ltin g f r o m high
t e m p e r a t u r e s , a finding which is s u b sta n tia te d by the w ork of
Sim onds (1942) who r e p o r t e d m a r k e d splitting of the a b s c is s io n
l a y e r s in Hub us c a n e s ,

Mix*s w ork of 1916 found the youngest

x y le m c e l l s w e re the f i r s t to be in ju re d , c o n t r a r y to what was
o b s e r v e d in Thuja,
L e th al t e m p e r a t u r e s of living c e lls have been a s o
c e r t a m e d to ra n g e f r o m 113 to 131 F fo r m o s t p la n ts (Clum,
1926a).

H ig h er t e m p e r a t u r e s w ere com m on u n d er polyethylene

c o v e r s during the e x p e r im e n t.
I n c r e a s e d m e tab o lic a ctiv ity of the plan t c a u se d by
th e h ig h e r t e m p e r a t u r e m a y have b e e n a cau se of in ju ry .

While

th e p e r io d of tim e a p la n t was capable of w ithstanding in ju ry
b ro u g h t about by high r e s p i r a t i o n r a t e s , high a i r t e m p e r a t u r e s
and high t r a n s p i r a t i o n r a t e s w as not d e te rm in e d , it s e e m e d likely
th a t a p e r io d of 1 to 2 days would be a m a xim u m .
The u s e of t r a n s p a r e n t polyethylene film a s a p r o ­
te c tiv e c o v e r fo r o r n a m e n ta l p la n ts cannot be re c o m m e n d e d to
r e p la c e the s c r e e n s s u g g ested by Thom pson (1940),

Although

t r a n s p a r e n t polyethylene was found by Sweet (1953) to be an e f ­
fe c tiv e m e a n s of c o n s e rv in g m o i s t u r e in potted p la n ts , it was

mot satisfactory for outdoor trees and shrubs because extreme­
ly high, temperatures developed beneath,
:

Transparent polyethylene film in the field deter -

iorated to the extent of splitting when exposed to climatic condi­
tions of Michigan during February and March of 1954.

SUMMARY

D iffe re n t tr a n s p la n tin g tech n iq u es w e re studied
to e v a lu a te th e e ffe c ts of add itio n al w a te r and one ppm in d o le ­
a c e tic a c id so lu tio n , ta k e n up by the p la n t a s a r e s u l t of e v a ­
cu atio n of a i r o r soaking the r o o ts .

Using the am ount of lin e a r

g ro w th and d ev elo p m en t of l a t e r a l b r a n c h e s of Syringa v u lg a ris
cv. T h u n b erg , F o r s y t h i a s p e c ta b ili s , and the yield of f r u i t of
c u l t i v a r s Golden Q ueen and Red C h e r r y of L y c o p e rs ic u m
e s c u le n tu m c o n t r a s t s in grow th w e re r e c o r d e d .
T r a n s p a r e n t polyethylene film c o v e r s (n o n - p e r f o r a te d and p e r f o r a t e d by two 6 - m m openings p e r s q u a re foot)
w e r e u s e d in an e ffo rt to p r e v e n t in ju ry of Thuja o c c id e n ta lis cv.
n i g r a u n d e r fie ld c o n d itio n s.

T e m p e r a tu r e flu ctu atio n s w e re

d e te r m in e d f r o m th e rm o c o u p le s atta ch ed to a "M inneapolis Honeywell B row n e le c tr o n ik " continuous te m p e r a tu r e r e c o r d e r ,
and r e la tiv e h u m id itie s by " B e n d i x - F r i e z 1* h y g ro th e rm o g ra p h s .
Stem s a m p le s w e re co llected fr o m ra n d o m iz e d
lo c a tio n s on u n tr e a te d , n o n - p e r f o r a te d and p e r f o r a te d t r a n s p a r e n t
p o ly e th y len e c o v e r e d p la n ts in the field, killed in f o r m a l in - a c e t ic alco h o l, d e h y d ra te d with t e r t i a r y - b u t y l alcohol, em bedded in
p a r a f f in ,

se ctio n ed eight m i c r a in th ic k n e s s , and stain ed with

s a f r a n i n and a n ilin b lu e .

S ections f r o m a p p a re n tly u n in ju red

b r a n c h e s , o n e - h a lf s to r e d d ry , the r e m a in d e r in tap w a te r
w e r e su b je c te d to v a ry in g le n g th s of tim e (15, 30, 60 and 120
m in u te s ) and t e m p e r a t u r e s 32 to 140°F b e fo re the p r e p a r a t io n
of s l i d e s .
G rowth ch an g e s w e re not u n ifo rm o r c o n s is te n t
f o r a ll p la n ts .

The n u m b e r of b r a n c h e s on t r e a t e d p lan ts of

S y rin g a w as in c r e a s e d , w h e r e a s F o r s y t h i a w as d e c r e a s e d by
tre a tm e n t.

L y c o p e r s ic u m e s c u le n tu m cv. Golden Queen showed

no sig n ific a n t d if f e r e n c e s in n u m b e r o r weight of e ith e r e a r ly
o r to ta l p ro d u c tio n .

The c u ltiv a r Red C h e r r y , how ever, when

t r e a t e d w ith w a te r p ro d u c e d significantly few er f r u it than
e i th e r the u n tr e a te d o r in d o leace tic a c id t r e a t e d p la n ts .
L ik e w is e , c e r t a i n annual flow ering p la n ts exhibited
a v a rie ty resp o n se.

F lo w e rin g of Salvia splendens was delayed by

in d o le a c e tic a c id t r e a t m e n t .
T e m p e r a t u r e s of the a i r and te m p e r a t u r e s un d er
po ly eth y len e f ilm w e re found to fluctuate widely durin g M a rc h 1954.
T e m p e r a t u r e s of u n p ro te c te d p la n ts w e re c o n s is te n tly lo w er than
th o s e of the c o v e r e d p la n ts .

A re d u c tio n of t e m p e r a t u r e of f r o m

1 to 3 ° F w as o b s e r v e d u n d er p e r f o r a te d as c o n tr a s te d with non-

p e r f o r a t e d p o ly e th y len e f il m .

Soil t e m p e r a t u r e s r e m a in e d n e a r

f r e e z i n g d u rin g the m onth of M a rc h .
In ju ry of two ty p e s o c c u r r e d : (a) d e s ic c a tio n a c c o m ­
p a n ie d by brow ning; and (b) d e s ic c a tio n without brow ning, u sually
being lig h t g r e e n o r yellow and b r i t t l e .

R elativ e h u m id ities

flu c tu a te d f r o m 100 p e r c en t d u rin g the p e r io d s of lo w est t e m p e r ­
a t u r e s to a p p r o x im a te ly 20 p e r cen t during p e r io d s of higher
te m p e ra tu re .
L e a v e s of Thuja o c c id e n ta lis cv. n ig r a p o s s e s s e d
a heavy c u tic le .

The e p i d e r m is was a single la y e r of c e lls with

r a t h e r heavy w a lls .

The p e r ip h e r a l w alls w e re g e n e ra lly convex.

F e w e r s to m a ta w e re found on the ab ax ial s u rfa c e than on the
a d a x ia l s u r f a c e .

The h y p o d e rm is , com posed of collen ch y m a

c e l l s , was a d ja c e n t to the e p i d e r m is .

The m eso ph y ll w as c o m ­

p o s e d of i r r e g u l a r l y shaped p a re n c h y m a c e lls fille d with c h lo ro p la sts.

T h ere w ere la rg e in te rc e llu la r spaces.

The vein c o m ­

p o s e d of ad a x ia l x y le m and ab ax ial phloem was s u rro u n d e d by
tr a n s f u s i o n t i s s u e , which in tu r n was bounded by a s in g le - la y e r e d
h e a v y - w a lle d e n d o d e r m is .
S to m ata w e re sunken, bounded by s u b s id ia r y c e lls
w hich a r c h e d o v e r the so m ew h at lig n ified g u ard c e l ls .

In o ld e r

l e a v e s , one o r m o r e r e s i n d u cts w e r e lo c a te d on the ab ax ial
side of the le a f .

In o ld e r s te m s , p ith p a r e n c h y m a p o s s e s s e d

heavy c e llu lo s ic w a lls .

Ray c e lls w e re in uni s e r ia t e ro w s,

elo n g ated to w a r d th e p e r ip h e r y of the s te m .
In ju ry on u n c o v e re d p la n ts o r ig in a te d on south
o r so u th w est e x p o s u r e s of the p la n ts .
a r e in a c tiv a te d by d ep o s itio n p r o d u c ts .

The e p id e r m a l c e lls
P a l i s a d e - l i k e c e lls

and m e s o p h y ll c e l l s a p p e a re d shrunken, and p o s s e s s e d la r g e
in tercellu lar spaces.

X ylem c e l ls w e re little affected, but

th e tr a n s f u s i o n t i s s u e s w e re c o lla p se d .

E n d o d e rm a l c e lls

w e r e slig h tly sh ru n k en .
Under the t r a n s p a r e n t polyethylene c o v e r s , the
le a v e s w e r e f i r s t p ale g re e n , yellow and finally brow n.

C e ll­

u l a r c o n te n ts of a ll t i s s u e s w e re atro p h ie d , with dense tannin
m a t e r i a l s being d ep o sited in the e p id e r m a l and h y p o d erm a l
c e ll lu m e n s .

A ll p a r e n c h y m a c e lls , r e g a r d l e s s of lo c atio n

in th e le a f o r s te m w e re shrunken, contained d ep o sits of
ta n n in s and w e r e m is s h a p e n .
The c e l ls of the c u tic le , e p id e rm is and h y p o d e rm is
of l e a v e s and s te m s , which had been a r tif ic a lly fro z e n , w ere
not o b s e r v e d to differ f r o m u n in ju re d t i s s u e s .

The lo c atio n of

86.

p a r e n c h y m a c e l l s w as a l te r e d , som e p la s m o ly s is o c c u r r e d ,
but p r in c i p a ll y in ju ry w as o b s e r v e d a s ru p tu rin g and s e p a r a tin g
of c e ll w a lls .
A r tif ic a lly in ju r e d le a v e s and s te m s p o s s e s s e d
a tro p h ie d c e l l s in the e p i d e r m is , e n d o d e rm is , and p a re n c h y m a
c e l l s r e g a r d l e s s of lo c a tio n .

D ep o sitio ns of tannin m a t e r i a l s

w e r e p r e v a l e n t in a ll of th e s e c e l l s .
O b s e rv a tio n s showed th at in j u r ie s , induced a r t i ­
f ic a lly by f r e e z in g , w e re not of the sa m e type or m agnitude
a s th o s e p ro d u c e d a r ti f ic a l ly by high t e m p e r a t u r e d e s ic c a tio n .
T r a n s p a r e n t p o lyethylene film w as an u n s a tis f a c to r y co v er
fo r woody p la n ts b e c a u s e of high a i r t e m p e r a t u r e developing
w ithin the c o v e r, and b e c a u s e of the ra p id d is in te g r a tio n of
th e p l a s t i c .

I n ju r ie s of u n tr e a te d p la n ts , p la n ts c o v e re d with

t r a n s p a r e n t p e r f o r a t e d and n o n - p e r f o r a te d polyethylene film
w e r e s i m i l a r to th o se p ro d u c e d a r tif ic a lly by high t e m p e r a t u r e .
Sixteen f ig u r e s and fo u rte e n ta b le s w e re included.

87

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