MORPHOLOGICAL ABD HISTOLOGICAL RESPONSES OF THE CHURRY
(FRTJNUS AVIUM L. ABD FRUBU3 CERASUS L. )
TO FALL APPLICATION OF PLANT GROWTH REGULATORS

By
SUBDARAM KRI3HNAMJRTHI

A THESIS
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied science
In partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY

Department of Horticulture

1949

AC KKOW LSDO-MEM TS

The author is deeply indebted to Dr, H* B, Tukey,
Professor of Horticulture ana Head of the Horticulture
Department, Michigan State College, for not only hie
guidance of the work connected with the thesis, but also
hie unfailin^ friendliness, help and courtesy without
which the task would have seemed much harder, and above
all for inspiring, by personal example, a correct phil­
osophy of research which the author has tried to learn
and which has greatly helped in the conduct of research
connected with the thesis.
Thanks are due to Dr, E. F. Woodcock, Professor of
Botany, Michigan State College, for the readiness with
which he gave every help that was requested of him, in
technical advice and equipment, connected with anatomical
work.
The author is grateful to Dr. C. L. Hamner, Professor
of Horticulture, Michigan State Colie e , for kindly going
through parte of the thesis and making very helpful
suggestions; to Dr. E. J. Benne, Professor, Department
of Agricultural Chemistry, Michigan State College, for
kindly analysing and providing data for the chemical
composition of the fruits; to Professor A. E. Mitchell,
Department of Horticulture, Michigan State College, for

applying- the necessary spray to the cherry trees, and
to the staff of tlie Horticulture Department, Michigan
State College, in general for their kind co-operation
and help whenever needed.

MORPHOLOGICAL AND HISTOLOGICAL RESPONSES OF. THE? CHERRY
(PRUNES AVIUM 1. AND PRUNES CERASES L. )
TO FALL APPLICATION OF PLANT GROWTH REGULATORS

By
SUNDARAM KRISHNAJMUR THI

A THESIS
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied science
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY

Department of Horticulture

1949

ACKNOWLEDGMENTS

The author is deeply indebted to Dr. H. B. Tukey,
Professor of Horticulture and Head of the Horticulture
Department, Michigan State College, for not only his
guidance of the work connected with the thesis, but also
his unfailing friendliness, help and courtesy without
which the task would have seemed much harder, and above
all for inspiring, by personal example, a correct phil­
osophy of research which the author has tried to learn
and which has greatly helped in the conduct of research
connected with the thesis.
Thanks are due to D.r, E. F. Woodcock, Professor of
Botany, Michigan State College, for the readiness with,
which he gave every help that was requested of him, in
technical advice and equipment, connected with anatomical
work.
The author is grateful to Dr. 0. L . Hamner, Professor
of Horticulture, Michigan State College, for kindly going
through parts of the thesis and making very helpful
suggestions; to Dr, E. J, Benne, Professor, Department
of Agricultural Chemistry, Michigan State College, for
kindly analysing and providing data for the chemical
composition of the fruits; to Professor A. E. Mitchell,
Department of Horticulture, Michigan State College, for

applying the necessary spray to the cherry trees, and
to the staff of the Horticulture Department, Michigan
State College, in general for their kind co-operation
and help whenever needed.

C 0 N T S .N T

Pae-e
Introduction

1

Review of Literature

3

Growth Regulator Studies

3

, Beans
Tomatoes
Other herbaceous plants
Herbicidal effects
Effects of soil and seedtreatments
Special studies of formative effects
Fruits other than cherries
Cherries

3
7
9
12
13
14
16
21

Studies on Morphology, Growing Habits and Development
of Cherries
22
Materials and Methods

25

Results

29

Tree Injury

.

29

Reduction of leaf area
Reduction of fruit-set
Factors in injury
Nature of injury
Varietal differences

.

29
30
30
31
32

Observations Connectedwith Abscission
The leaves in the fall
Previous season fruits
Flowers and f1ower-parts
Mature fruit
The style
Discussion
Effects of the Opening

32
32
33
33
34
3435

ofFloral and Vegetative Buds

Floral buds of sour cherry
Growth of buds up to the bloom stage
Opening of buds
Floral buds of sweet cherry

37
37

37
39
40

Leaf buds

41

General observations
Sour cherry
Sweet cherry

41
41
43

Discussion

42

Formative Effects and Histological Studies

44

The fruit

44

Oomparati\e description of the treated
fruit
Development of the fruit
Histological observations of the
develooing fruit
Cellular details

44
51
53
57

The pedicel

60

General observations

60

Other parts of the flower
The
The
The
The
The

66

receptacle
calyx
corolla
stamens
pistil

67
67
68
70
71

The leaf

71

External modifications
Internal structure
Discussion.
The shoot growth in spring

7173
74
andsummer

Other Observations
Influence on the storage cuality
Influence on composition of fruit
General Discussion
Translocation of Stimulus

75
78
. 80
81
84
84

The Order in Succession of Responses
The Vascular System

86

»

83

Other Histological Responses

91

The Size

91

Shape of Form

93

The Preponderent Effect of 2,4-dichlorophenoxyacetic acid

98

Practical Applications

99

Importance to the fruit grower

99

Importance to the taxonomist or systematic
pomologist

100

Importance to the horticulturist

101

Importance to the geneticist

102

Summary

104

Bibliography

110

Plates

121

A. Prowth Regulator Studies

1. Beane
Among the noteworthy investigations on the effects
of plant growth regulators, have b een the studies of their
histological effects on bean plants.

Kraus, Brown and

Hamner (51) found the endodermis and cambium the most re­
sponsive to application of indoleacetic acid, the endo­
dermis proliferating and differentiating into vascular
strands, and the cambium cells proliferating rapidly but
with delayed differentiation of derivatives.

The primary

phloem was also highly sensitive w i t h abundant prolifera­
tion and frequent radial elongation.

The epidermis and

pericycle were not very responsive while the p ith prolif­
erated slowly but profusely.

Hamner and Kraus

their observations over Kraus, Brown and Hamner

(43) extended
(51) to

indolebutyric acid and naphthaleneacetic acid with similar
results.

Kraus and Mitchell

(52) reported the histological

responses of the bean to naphthaleneacet&mide.

There was

less extensive proliferation than w it h indoleacetic acid
and the most evident feature was the great increment of
secondary xylem, the decided thickening of the walls of
cells of most of the tissues composing the stem and the
partial suppression of elongation of axillary buds.

The

INTRODUCTION

Tukey and Hamner (96) reported in 1947 from field
observations that fall application of a spray mixture of
2 ,4-dichlorophenoxyacetic acid and naphthaleneacetic

acid to cherry trees, resulted, in delayed bloom and in
changes in form and composition of the fruit.

They noted

among-gross effects, injury to trees, delayed abscission
of abortive flowers and abortive fruits, elongate shape of
fruits with pointed apex and development of a strong vas­
cular system within the fruits.

Their data have been

summarised under ’’Review of Literature”.

These obser­

vations seemed to indicate the value of a. more detailed
study of the responses of the cherry (Prunus avium. L.
and Prunus cerasus, L.) to the fall application of growth
regulators.

This thesis is a report of such a study of

the morphological and histological responses, made at the
experimental orchard of the Michigan State College,

' REVIEW

of

literature

For a decade and more, morphological and histological
effects of plant growth regulators have been rather inten­
sively studied.

This review describes the responses of

plants that are generally characteristic of the particular
substances used, for example the formative effects of
phenoxy compounds and. unless the differential effects of
concentrations are a factor,

they will not be mentioned.

The literature has been classified under the following
groups:
A. Growth Regulator Studies
1. On beans
2. On tomatoes
3. On other herbaceous plants
4. On herbicidal effects
5. Effects of soil and seed treatments
6 . Special studies of formative effects

7. Studies with fruits other than cherries
S. Studies w i t h cherries
B. Studies, on morphology , growing habits and development
of cherries.

A. Growth Regulator Studies

1. Beane
Among the noteworthy investigations on the effects
of plant growth regulators, have been the studies of their
histological effects on bean plants,

Kraus, Brown and

Hamner (51) found the endodermis and cambium the most re­
sponsive to application of indoleacetic acid, the endo­
dermis proliferating and differentiating into vascular
strands, and the cambium cells proliferating rapidly but
with delayed differentiation of derivatives.

The primary

phloem was also highly sensitive with abundant prolifera­
tion and frequent radial elongation.

The epidermis and

pericycle were not very responsive while the pith prolif­
erated slowly but profusely.

Hamner and Kraus (43) extended

their observations over Kraus, Brown and Hamner (51) to
indolebutyric acid and naphthaleneacetic acid with similar
results.

Kraus and Mitchell (52) reported the histological

responses of the bean to naphtha!eneacetamide.

There was

less extensive proliferation than with indoleacetic acid
and the most evident feature was the'great increment of
secondary xylem, the decided thickening of the walls of
cells of most of the tissues composing the stem and the
partial suppression of elongation of axillary buds.

The

— 4—
effect was similar in the African Marigold and in
Mirabilis.

Another most obvious characteristic was the

increased firmness of the treated internodes, resulting
in prevention of abscission, when decapitated and treat­
ed.

Among other effects were the reduction in the

height and total leaf area, and reduction in size of
primary leaves.
Mitchell and Stewart (6 8 ) compared the effects of
naphthaleneacetic acid and naphthaleneacetamide upon the
bean.

They showed again the tendency of the acetamide

to increase the wall material, especially of the xylem
and the pericycle fibers, and not to affect the cortex.
They made other observations that the treated leaves
were lighter green in color and thicker, that the abscission
of cotyledons.was delayed by several days, and that treat­
ment inhibited bud development.

Hullison (71) observed

that application of tetrahydrofurfuryl butyrate induced
certain different responses from those obtained from other
growth substances, among which 'were the more localized
response, the highest activity' of the xylem and. moderate
activity of the endodermis with no differentiation of
vascular tissue.
Hamner (38) found that A-naphthaleneacetamide when
applied to the bean in nutrient solution reduced top

-5growth and increased root growth, and induced earlier
maturity and greater extension of xylem and phloem in
the roots.

Palser (79) observed that Vicia faba respond­

ed to indoleacetic acid histologically with activity to
some extent in every parenchymatous tissue, and--notably
with somewhat extensive vascularisation of derived
tissues.

Beal (IS) applied 4 substituted phenoxy com­

pounds and found that in the second internode nearer
the point of application, with the exception of the epi- .
dermis, possibly the pericycle and limited portions of
outer cortex, all the other tissues responded actively,
whereas in the first internode and hypocotyl, farther
from the point of application, only the endodermis, cam­
bium, phloem and ray parenchyma were activated.

Whiting

and Murray (106) reported that histological reactions of
bean to phenylacetic acid consisted of marked prolifer­
ation of inner cortical parenchyma,, endodermis and primary
phloem parenchyma., also of the activity of the outer
cortical parenchyma, the rays, and the peripheral pith,
and the cambium, with slight response in the pericycle
and secondary phloem-, and no activity of the epidermis
and the central pith.
Swanson (8 6 ) studied the histological responses of
the Red Kidney bean to aqueous sprays of 2,4-dichloro-

-6—
p h e n o x y a c e t i c acid and noted the activity in the endo­
dermis,

pericycle

(if undifferentiated or embryonic),

p h l o e m parenchyma, cambium .and rays (the latter two zones
b e i n g v e r y active).

He found that the formation of xyla.ry

e l e m e n t s was greatly inhibited and when occurring, much
disorganized; that cortex showed little response; and
e p i d e r m i s and pith no response.

He observed that the

effect

of 2,4-D was systemic in nature, even at relative­

ly l o w

concentrations and in this respect, it differed

from o t h e r growth regulating substances.
Whiting

Murray and

(76) applied 2,4-D acid and four of its salts to

d e c a p i t a t e d stem of kidney bean plants and found similar
h i s t o l o g i c a l responses in the early stages, with initia­
tion,

s o o n after treatment, of proliferation of the paren­

chymatous
dermis,
Weaver
parts

tissues of the inner cortex including the endo­

of the pericycle, phloem, cambial zone and rays*
(ICO) in studying the subsequent growth-of various

of

red kidney bean and soya- bean plants sprayed

with 2 ,4— dichlorophenoxyacetic acid observed that the
p r i m a r y leaves of treated plants were much heavier and
that t h o s e of red kidney beans remained green and attached
to t h e

pl a n t s long after those of the controls had with­

ered a n d fallen, that the growth regulator inhibited the
gr o w t h in length and width of leaflets which developed

-7after treatment, and delayed the onset and decreased the
amount of pod-formation.
Murray and Whiting (75) studied the histological re­
sponses of bean stems to low concentrations of indole­
acetic acid and compared with those described by Kraus
(50) for tryptophane.

The important differences between

the two substances were that with tryptophane, the cor­
tical parenchyma was more reactive, vascularisation in
proliferated endodermis greater, primary phloem less
active, pith relatively inactive and the course of vascularisation in other tissues different for the two sub­
stances.
Laibach and Fishnich (54) observed the histological
effects of indoleacetic acid upon coleus, Vicia faba and
the tomato and noted in coleus that new vascular bundles
appeared among the three originally present on each side.

2. Tomatoes
Tomato is another plant which has received attention
from workers not only in connection with effects of growth
regulators on fruit-set but also as an experimental
material, for morphological and histological studies.
Borthwick, Hamner and Parker (18) studied the histological
response .of tomato stem to indoleacetic acid.

The results

-8were quite similar to those reported previously for the
bean.

Cortical enlargement occurred, accompanied by some

division; the endodermis divided actively; the phloem
and the wood parenchyma proliferated, while the epidermis
and pericycle were not very responsive.
Bausor, Reinhart and Tice (9) reported the response
of tomato stem to treatment with B-ns.phthoxyacetic acid,
in the young stem, there was enlargement of the cortical
cells and great activity of cambium and differentiation
of secondary xylem.

In older stems the cortex was also

activated but the greatest change occurred in the tissues
from cambium to endodermis inclusive in which prolifer­
ation took place rapidly.
Hamner, Schomer and Marth (40) in using growthregulating substances in aerosol form for fruit-set in
tomato found among other observations that as a result
of the use of B-naphthoxyacetic acid, the style persisted
longer and was enlarged and the treated tomatoes ripened
earlier, were larger in diameter and heavier than controls
and some fruits were "mis-shapen", and there was budinhibition and leaf "malformation".
Murneek, Wittwer and Hemphill (74) found in their
experiments with greenhouse tomatoes that sprays of pchlorophenoxyacetic acid and 2,4-dichlorophenoxyacetic

-9acid at certain concentrations had a strong morphogenetic
effect on meristematic tissues resulting in elongation
of internodes, modification of newly formed leaves and
abnormal growth of pericarps.

In the case of 2,4-D, and

chlorophenoxyacetic acid as a whole, notable was the
influence on the development of fruits 'which at maturity
became unusually large, mostly pointed, softer, with an
orange color.

The authors concluded that some of these

chemicals stimulated directly or indirectly the growth
of the outer region of, the pericarp.

Murneek (72) con­

firmed in further investigations the formative influences
of p-chlorophenoxyacetic acid and cautioned that in
spraying of a whole plant for fruit-set, the spray should
avoid the growing points to prevent undesirable formative
effects.

3.

Other Herbaceous Plants

Ennis, Swanson and others. (31) reported that 3,4,5trichlorophenoxyacetate significantly reduced the yield
of potato tubers, stunted the vegetative growth, showed
swelling of the pulvini and thickening of the stem im­
mediately adjacent to the petiole.

Goldberg (36) applied

indoleacetic acid to cabbage stem and found that all
tissues responded to some extent; most generally respon3

-10sive were those of phloem, rays and pith.

The cambium,

cortex, endodermis, and xylem were moderately stimulated,
while epidermis and pericycle' reacted weakly. Harrison
(45) treated Iresine lindenii with indoleacetic acid.
The endodermis and cortical parenchyma were not very
reactive,- while.the phloem, pericycle, rays and extrafascicular cambium proliferated.
of the collenchyma was also noted.
bium was not very responsive.

Thinning of the walls
The fascicular cam­

Of rather unusual response

was the proliferation of cutinised epidermal cells with
thickened walls.

The general degree of activity of

Iresine resembled more closely that of the tomato than
of the bean.
Beal (10) worked on three species of Liliurn with
indoleacetic acid.

The rate of response was much slower

than that reported for bean, tomato and Iresine.

In

Liliurn philippinense and Liliurn longiflorum, there was
proliferation of the parenchyma cells centripetal to the
bundles, which later became organised into roots.

In

these, the outer cortex and the epidermis were only
slightly affected.

In Liliurn harrisii , however, the

epidermis and the cortex in the axil of the leaf were
activated to divide and become organised as buds.
Hamner (43) worked on Mirabilis jalapa with indoleacetic acid and found wide variation in histological re-

-11sponses of

tlie various tissues.

The pericycle, inter­

f a s c i cular parenchyma just inside it and the interfas­
cicular c a m b i u m (in the older stems) were the most re­
active,

while

responsive,

the vascular tissues were generally un­

t h e epidermis and cortical parenchyma showed

little r e s p o n s e and the endodermis considerable.
pith w a s

The

s l o w to start activity but once it started,

proliferated, rapidly, differentiating as internal roots
or as s t r a n d s
Blum

of vascular tissue.

(IS) worked on sunflower stem and found that

n a p h t h a l e n e a c e t i c acid caused marked epinasty, completely
inhibited b u d

development, caused extreme development and

d i f f e r e n t i a t i o n of secondary xylem and marked development
of a c t i v i t y
Beal

of the horizontal cambium.

( 1 1 ) treated sweet pea with 4-chlorophenoxyacetic

acid a n d o b s e r v e d stem curvature, epinasty, inhibition of
buds,
cycle.

s w o l l e n root-tips with most proliferation of peri­
P f e i f f e r (80) worked on the aerial roots of

Cis.sus s i c y o i d e s L. with indolebutyric acid and found that
the cells of

the phloem and pericycle proved most reactive,

enlarging a n d dividing, with derivatives of the pericycle
opposite t h e

protoxylem forming the lateral roots.

-134.

Herbicidal Effects

Tukey, Hamner and Imhofe (97) were the first to study
histological effects of herbicidal concentrations of 2,4-D
and the experimental plant materials were bindweed and
sow-thistle.

In the bindweed, the pollengrains were plas-

molysed and disorganised, flowers arrested in development,
chlorophyll formation checked and cell division activited
in the large vascular bundles of the leaves.

The majority

of the cells in the leaves were plasmolysed.

Cell division

was greatly increased in all cambial zones and phloem
regions of the stem and rhizomes.

Enlargement and rup­

ture of cortical cells were conspicuous.

In the rhizome

of sow-thistle, the reactions of cortex, cambium and
phloem zones were similar.

Hamner and Tukey (41) in study­

ing the herbicidal action of 2,4-D on several shrbus,
vines and trees, noted marked proliferation of the region
outside cambium leading to splitting of the bark, curva­
ture of new shoots and downward bending of petioles.
Young trees were more responsive than old ones and in
general, plants which had just broken dormancy in the
spring and were making new growth were more sensitive to
treatment than plants with fully developed foliage.
Pridham (Si) studied the delayed action of 3,4-D on
trees, shrubs, and perennials, sprayed in the fall and
observed delayed bud-break in spring and production of

-

13-

distorted foliage, excessive serrations, exaggeration of
length/width ratio of leaves, prominence of veins and
thickening of leaf.

5.

Effects of Soil and Seed Treatments

While upto this stage, the literature has dealt with
direct application of growth regulators to plants or trees,
it is relevant to state that some workers have experimented
with treatment of soil or seed with growth regulating
substances and noted the subsequent effects on plants,
Allard, DeRose and Swanson (1) found that treatment of
seeds of several crop plants with 2 ,4-dichlorophenoxyacetic acid, 4-chlorophenoxyacetic acid, 2 ,4,5-trichlorophenoxyacetic acid in general inhibited germination, de­
creased the growth of young seedlings, and caused abnor­
malities in the anatomy of the seedlings.

As examples

of the latter in the hypocotyl of kidney beans were the
delay in the maturation of the primary conductive tissues,
failure of the pith to split to give rise to a hollow
stem, enlargement of cortical and pith cells and slight
stimulation of cell-proliferation in regions of the pri­
mary phloem and the rays.

Hamner, Moulton and Tukey (39)

treated in one case soils with 2,4-D prior to sowing and
in another soaked the seeds in solution of 2,4-D and in
both cases, seedlings of beans exhibited characteristic

formative effects and "virus-1 ike11 symptoms.

S, Special Studies of Formative Effects
Of particular importance to the subject of this thes
are the series of papers on formative effects of growth
regulating substances presented by Zimmerman and Hitch­
cock (110, 111, 112), and Zimmerman (109, 114).

Zimmer­

man and Hitchcock (110) treated several species of plants
with solutions and vapors of B-naphthoxyacetic acid and
its derivatives and found that in the new leaves that
were formed after treatment, there was modification of
the venation pattern and form.

They varied from frenched

or fern leaf types to simple leaves.

The leaflets often

failed to separate on one side of the mid-rib giving a
different appearance to the two sides of the leaf.

In

many respects, the leaves resembled those of virus-dis­
eased or mite-infested plants.
clearing of the veins.

There was pronounced

Vfith treatment of soil with the

solutions of haphthoxyacetic acid, the effects were even
more pronounced and more lasting.

The flower-buds of

tomato plants treated, by way of soil were abnormally long
with a decided calyx tube, separating only at the tip.
The floral parts —

petals, stamens and styles —

per­

sisted for an abnormally long time-during parthenocarpic

-15development .
B — raaplrfclioxy
above

but

dril, s

of

and

tbe

Zimmerman (109) in further experiments with
c o m p ounds, not only confirmed the findings

also

f o u n d that they modified the simple ten­

c/uc-umbers into branched and leaf-like structures,
sise

a n d shape of flower-buds and fruits.

Zimmerman

and

influence

of

Hitchcock (112) reported that under the
tri-iodobenzoic acid, a hormone-like sub­

s t a n c e , a x i l l a r y buds which normally produced leafy shoots
were
the

induced
plant

ated

in

t o grow f l o w e r - c l u s t e r s T h e main shoot of

also

f l o w e r — clusters.

Zimmerman
lasting

nature

acid

with

lilce

compounds

vision

of

low

.acid

of t h e responses of dichlorophenoxyacetic

and also showed that in tomato, cell di­
cambium and various parts of the cortex was

w i t h i n 24 hours, by chlorophenoxy compounds.

observations
on

part s ,

tomato
and

reported

acids

grew

siae,

shape,
those

of the effect of chlorophenoxyacetic

were bud-inhibition, persistence of floral

formative

(1X4)

like

and Hitchcock (111) emphasised the more

concentrations compared to other hormone-

the

accelerated
Other

lost the shoot producing bud and termin­

influences on the leaves,

Zimmerman

that plants treated with active xelenoxy

m o d i f i e d leaves differing from the normal in
pattern,

of- virus

texture and venation, and appearing

diseased plants.

Burton (26) studied

-16the formative effects of substituted chlorophenoxy com­
pounds and found, that treatment of young plants with 0.5
per cent concentration of 2-chlorophenoxyacetic acid in
carbowax inhibited the formation of intercellular spaces
in the mesophyll of bean leaflets.

Similar application

of 0.5 per cent 4-chlorophenoxyacetic acid in lanolin
inhibited the activity of plate meristem in the laminae
of bean leaflets.

Similar treatment with 0.5 per cent

concentrations of 2,4-dichlorophenoxyacetic acid, in either
lanolin or earbowax as the carrier induced progressive
modification of bean leaves.

The earliest leaves were

similar to those induced by treatment with 2-chloro­
phenoxyacetic acid.

In later leaves, the external form

and internal structure resembled that found in leaflets
of plants treated with 4-chlorophenoxyacetic acid.

7.

Fruits Other Than Cherries

Marth and Meader (58) used four compounds, indoleacetic, indolebutyric, B-naphthoxyacetic and 4-chlorophenoxyacetic acids on somewhat unfruitful blackberry
selections at the time of flowering and obtained sig­
nificant increase in berry weight and reported that the
treatments stimulated the development of the receptacle
and of the pulp of the individual drupelets and increased
the number of drupelets and seeds per f ruit but many of

-17—
the seeds were small and undeveloped so that the ratio
of seedweight to fresh berry weight was actually less
in treated fruits than in control.
Clark and Kerns (28) reported data obtained from
pineapple plants treated with naphthaleneacetic acid
after completion of normal floral differentiation but
prior to actual blossoming.

Higher concentrations in­

creased the weight of the fruit and delayed ripening a
week or more, and no treatments induced anatomical effect
within the flesh of the fruit, but,the concentration of
the juice of treated fruits was about 2° Brix lower than
that of the controls.

Treatments did not also affect the

number of fruitlets per spiral.

High concentrations

induced longer and thicker peduncles and difficulty in
separating the fruits from the peduncles.
Stewart and Klotz (8 8 ) brought to attention some
unusual effects of 2,4-D on the morphology of oranges.
Young Navel orange fruits sprayed with concentrations
varying from 25 to 225 p.p.m. of 2,4-D developed seeds
or seed-like structures.

The highest concentrations in­

duced a thick rind and excessively large, protruding
navels, in some fruits and cylindrical shape and small
navels in others.

When applications were made during

the period of full bloom, all treatments induced a down­

-18ward and inward rolling of the margins of the young,
expanding leaves, the response decreasing with lower con­
centrations; la,ter prevented flower-drop tout reduced
fruit-set.

It was found that the blossom-retaining effect

was not transmitted from the sprayed portion of the tree
to the unsprayed area.

In Valencia, the high concentra­

tions caused a curious pebbling of the peel of the green
fruit due to outward and inward elongation of the oil
glands, and highly marked thickness of rind of the
sprayed fruits.

Some fruits became cylindrical in shape

and developed a small navel "complete with juice-vesicle,
and a persistent style".

Lower concentrations increased

fruit si2e by 25 per cent, but at the expense of commer­
cial quality.
Nixon and Gardner (77) reported that application of
naphthaleneacetic acid to dates, in higher concentrations
of aqueous solutions of 0.1 and 0.01 per cent inhibited
development of carpels but caused the enveloping peri­
anths to persist and to show apparent enlargement in some
instances.

The strand with its persisting perianths was

still alive and normally colored long after they were
dead and dry in the untreated ones.

Naphthaleneacetic

acid at 0.01 per cent aqueous spray applied ten days
after pollination followed by 0.02 per cent six days later

-19reduced set by 50 per cent and induced a considerable
number of fruits with varying degrees of ’’malf ormation".
The dates ripened a little earlier.
Moon, Regeimbal and Harley (70) airplane sprayed a
small block of apple trees with 8100 p.p.m. 2,4-D in an
oil-emulsion, on November 9, 1946.

Stayman Winesap and

Winesap trees so treated held their leaves well into the
winter after all leaves were dead and long after untreated
trees were completely defoliated, and in the spring of
1947, numerous leaf petioles were still attached to the
branches, even though the blades had been broken off during
the winter.

Subsequently during the growing season, there

were typical signs of delayed foliation, badly deformed
primary leaves, death of lateral buds on terminal shoots
and of weaker spurs on older branches.

Similar response,

even more widespread, was obtained with 10 p.p.m. of
2 ,4-D butyl ester as groundspray of Stayman Y/inesap applied

on August 29 and September 11, as also tight adherence
of all subsequent blossoms and fruits killed by frost on
May 9 to 11.

These authors observed in addition the

residual effect of 2,4-D at 10 p.p.m. applied in August
29, 1946, for a full year later, in reducing harvest drop.
Bryant, Vincent and Schafer (22) observed that appli­
cations of 2,4-D made to bindweed in 1945 in late summer

in an apple orchard resulted, in abnormalities in the
apples harvested in 1946.

Some of the fruits showed only

rudimentary or no seed development.

McIntosh apples,

normally round oblate, had become oblong in shape with a
more open core, while Jonathan had changed from round
conic to oblong conic.

A considerable number of Jonathan

and Delicious apples were "doubles".

The authors consid­

ered that "these malformations may have come from the
3,4-D being transmitted through the roots of the trees,
from the material drifting at the time the bindweed was
sprayed, or from volatile materials in the spray itself".
Marsh and Taylor (56) applied 2,4-D on August 22,
1945, as an eradicant spray for poison ivy in an apple
orchard.

After cleaning and rinsing the spray equipment

with waiter as much as to remove all traces of odor and
visible evidence of the 3,4-D residue, applied an oil spray
one week later to control orchard mites.

In fall, fruit

and foliage in this Winesap and Stayman block adhered
tenaciously to the trees.

Through the winter, the foliage

hung on those trees "dry and brown like the leaves on
shingle oaks".

In 1946, the blossoming of this block was

7 to 10 days later.

The leaves were narrowed, deeply

serrated, epinastic, frequently mottled.
low amount of total foliage area.

There was a very

The adherence of un-

-31developed, dried apple blossom parts was very noticeable.
The fruit-set was very much reduced.

The apples were

prematurely ripened and not suitable for storage.

8. Cherries
Hitchcock and Zimmerman (46) have reported effects
of application of summer sprays of potassium napht’
naleneacetate to Montmorency cherry trees, in retarding open­
ing of buds.

The degree of inhibition varied with the

concentration of the substance, and the time the spray
was applied.

The vegetative buds were generally delayed

to a greater extent than flower buds.

The sprays of July

had the greatest retarding and those in September the
least.

The increased delay resulting from an increase in

concentration was relatively the same as that due to the
difference in time of application.

Flower buds located

on spurs were delayed to a greater extent than those on
one year old shoots.

The opening of flower buds was

delayed from a few days to 14 days depending on the con­
centration and time of applying the spray, and that of
vegetative buds similarly,up to 19 days.

Terminal vege­

tative buds were retarded to a lesser extent than side
buds.

The fruit-set on treated branches was delayed

slightly and appeared to be spread over a longer period
as compared to the controls.

Ripe fruit had the same

general appearance on the treated and control branches.
The experiments of the author also included those on '
varieties of apples, peaches, pears and plums, with sim­
ilar results but with a variation in resistance to the
material, the apple was slightly more resistant than
cherries, and peach and plum more sensitive than cherry.
Tukey and Hamner (48, 96) gave an account of obser­
vations of the effects of fall application of 3,4-D and
naphthaleneacetic acid to sweet and sour cherries and
brought out the facts of injury to twigs, buds and spurs,
delayed blossoming in the following spring, delayed ab­
scission of abortive flowers and abortive fruits, and
above all the elongate fruit with pointed apex, and strong
vascular development within both the fruit and the pedicel.

B. Studies on Morphology. Growing Habits and Development
of Cherries
Bradbury (30, 21) in making a study of the developing
and aborting fruits of sour cherries came to the conclu­
sion that lack of nutrition was the principal cause of
the abortion, particularly of the first drop fruits.
Chandler (27) described the nature and position of fruitbuds in cherries and stated that differentiation of buds
in cherries is discernible in early July.

-33Tukey (94) has described the growing and fruiting
habits of the sour cherry, making the distinction between
the shoot and the spur, and. mentioning the correlation
between the positions where the flower-buds are formed
and the continued fruitfulness of the tree.

In describing

the distinctive growing habits of the three major var­
ieties of sour cherry in the Hudson River Valley, he
.sums up the growing habit of Montmorency cherry thus:"Shoots over 6 inches in length tend to form leaf-buds
in contrast with blossom buds which are formed largely
by shoots less than S inches in length.

The leaf-buds

develop into spurs or strong lateral shoots — - mostly
spurs in the case of shoots between 6 and 15 inches in
length which bear repeatedly in subsequent years.

The

blossom-buds on one year old wood, however, fruit and
leave barren wood behind".
Tukey (95) reported three stages of pericarp devel­
opment in sour cherry; namely, I - a period of rapid in­
crease following fertilization, II - a period of delayed
increase during mid-season, and III - a second period of
rapid increase to fruit ripening.

He found the duration

of stages I and III nearly identical in the three var­
ieties tested and the duration of period of delayed in­
crease (Stage II) correlated directly with the season of
fruit-ripening.

-24Tukey and Young (98) made detailed histological
study of the development of the different tissues of
the sour cherry fruit (Montmorency variety), step by
step through the three stages mentioned above,, and corre­
lated the internal histological changes with the exter­
nal evidences of growth.

-25MATERIALS AND METHODS
Bearing trees of the Montmorency sour cherry (Prunus
cerasus L.) and of the Schmidt sweet cherry (prunus avium L.)
were selected in the experimental orchard of Michigan
State College, East Lansing, for treatment and study.
The trees at the time of treatment were fifteen to six­
teen 'years of age.

One sour cherry tree and one sweet

cherry tree were sprayed and one of each left untreated
for comparison.

The spraying was done on September 22,

1947, between 6 and 7 P.M. vath a Hydraulic Bean Sprayer,
20 gallon capacity, operating at 500 pounds pressure.
The discharge equipment included a single nozzle bean
gun equipped with No.. 10 disc.

The spray consisted of

100 p.p.m. of 2,4-dichlorophenoxyacetic acid in the
form of '"Dow 7 0 Wettable", a commercial product of the
Dow Chemical Company and 30 p.p.m. of naphthaleneacetic
acid in the form of "Endrop111, a commercial product of the
Shell Oil Company.

The method of spraying consisted of

spraying the whole tree thoroughly from top to bottom
until the spray material dripped from the leaves.

Collection, of Material
Samples of buds were collected beginning October 1.,
1947, at intervals of three weeks upto'the 20th of March,
1948, and at intervals of two weeks until the 22nd of

I

-26April, 1943.

From then on, the required plant materials

for examination or preservation were collected as fre­
quently as the needs arose.

Fixation, Sectioning and Staining
Subsequent to spraying, till the harvest of fruits,
the materials collected were all fixed in killing solution
of the following proportions
500 ml.

95 per cent alcohol

450 ml.

distilled water

31 ml.

glacial acetic acid

60 ml.

formalin

In the case of materials like stem, pedicel, leaf,
and certain stages of the fruit, it was easy to make suit­
able sections with the table microtome.

In many cases,

the tissues of such sections were clear enough without
staining so that semipermanent slides were conveniently
made with glycerin as explained by Sass (82).

In some

sections, however, to make a proper distinction between
lignified and cellulose walls, methyl green and Bismarck
brown were. used.

Certain stages of the winter buds were

utilized for making sections, for the sake of some con­
firmatory observations, by running up to paraffin, then
sectioning with a rotary microtome and staining with
Delafields hematoxylin.

-37In advanced, stages of fruit development when the
stony pericarp had begun to harden, freehand sections
for detailed study were made separately in the different
regions of the fruit outside the stony pericarp.
The epidermis of the leaves and fruits was examined
in surface view by stripping thin pieces with razor and
in both cases, no stain was needed to show good contrast.

Measurements and Drawings
Outline drawings, where no cell-details were desired,
were made with the use of a Bausch and Lomb triple purpose
micro-projector, using the same objective and a constant
set-up for the same set of comparative materials.

Detailed

drawings' were made with a camera lucida, to one scale for
the same set of comparative materials, to give identical
enlargements.
Many detailed measurements became unnecessary, be­
cause of the obviously large differences resulting from
treatment.

In an experiment of this kind, it is the com­

parative rather than the original measurements that stress
the nature of responses obtained by treatment.

Where,

however, to make a point clear, an original measurement
was necessary, it has been provided.
Besides this, the behavior-pattern of the sour cherry
and the sweet cherry has

been identical in so many respects

-28that to separate them in the treatment of subject would
be merely repetitious.

To avoid this, where there was

no need to refer to them separately, the expression
"cherry" has been used or no particular mention is made
of any of the cherries.
For histological studies, descriptions and. drawings,
sour cherry has been more freely used than sweet cherry
because of the advantage of detailed information on normal
development of sour cherry available from Tukey (95) and
Tukey and Young (98) and because of incompleteness of
materials from sweet cherry, due to injury.

An examin­

ation of the available materials from sweet cherry, how­
ever, showed no significant difference in general, except
for a tendency for a relatively greater accentuation of
response to treatment.
Even in the ce.se of sour cherry, to avoid the inter­
fering factor of injury, materials from the healthier
portions of the tree were utilised for observations of
direct responses to treatment.

The reasons for this

become clear from the description under "Tree-Injury".

.-29RESULTS
1. Tree Injury
Injury to trees as a result of application of high
concentrations of plant growth substances, particularly
of naphth.alenea.cet ic .acid and 3 ,4-dichlorophenoxyacetic
acid, has frequently been reported (65, 57, 93, 87, 56).
Such injury was also found in our experiments.

The

following is an account of the nature and extent of injury.

Reduction of Leaf Area
The most severe injury was to the leaf buds.

A large

proportion of them on the tree as a whole were killed.
This was reflected in the ultimate reduction of leaf
area.

Plates 2 and 4 show this condition of sour and

.’sweet cherry trees respectively, on July 13, 1943, in
contrast to the normal leaf area of the trees, as shown
in Plates 1 and 3.

The framework of the treated trees

in the photographs, because of lack of foliage, can be
easily traced to its intimate details, while it is com­
pletely .hidden from view by the foliage in the control trees.
The malformed and stunted leaves that emerged from
the inhibited leaf-buds as shown in Plates 5 and 7 also
contributed to the decrease in leaf area.

-30Reduction of Fruit-set
Compared to the yield of fruits from the untreated
trees, there was a great reduction, by 90 and 95 per cent
in the sour and sweet cherry respectively, as a result
of treatment.

Damage to fruit-buds was severe.

number of them were completely dead.

A great

A smaller propor­

tion of them were inhibited in varying degrees and while
opening subsequently, proved abortive later.

The ulti­

mate result of -reduced fruit-set is, however, attributable
to three causes, decrease in leaf area, damage to fruitbuds and injury to the tree as a whole.

Factors in Injury
While injury itself was a direct result of the treat­
ment, there were certain factors, chiefly light, vigor of
branches and the method of spraying adopted, that seemed
either to accentuate injury or to resist it.

The term­

inal portions of branches that had more light tended to
develop greater amount of foliage, whereas the inner
portions of branches were almost bare.
indicated in Plates 2 and 4.

This is clearly

The less vigorous branches

showed greater injury to buds and spurs on them than the
more vigorous ones.
Above all the very method of application of the spray,
vi 2 ., spraying the whole tree till the material dripped

—31—
from the leaves seemed to have created a situation in
which the drip from the topmost portions added on to the
amount of material on the lower portions of the tree,
creating a differential concentration with relatively
harmless lower concentrations in the upper levels and
relatively toxic higher concentrations in the lower
levels.

This is evidenced also by the difference in

intensity of responses that have been noted, which have
been correlated with difference in concentration by other
workers such as Hitchcock and Zimmerman (46).
Plate 2 shows clear indications of such a demarcation,
with better development of foliage at higher levels com­
pared to the relative bareness of lower branches.

This

distinction has been made use of in our experiments in
selection of materials for observations of direct responses
to treatment, to avoid as much as possible an intervening
factor like injury.

Nature of Injury
A closer examination of the twigs that were injured
showed small necrotic areas and brown fleckihgs either
in or under the bark.

Pronounced browning was notice­

able in the pith and xylem of spurs.

A few lower branches

of sweet cherry that were dead resembled winter injury
from an oil-spray.

-32Varietal Differences
In comparing the total effect of injury, it was
clear that the sweet cherry tree suffered more than the
sour.

This difference, is very clear from the appearance

of trees in Plates .2 and 4.

Varietal differences in

resistance to injury have been pointed out by Hitchcock
and Zimmerman (46).

2. Observations Connected with Abscission
From the time that the application of spray was made
to the cherry trees to the time of harvest of fruits, one
of the most conspicuous responses observed successively
was the noticeable delay or even complete prevention, of
normal abscission of plant parts.

The Leaves in the Fall
While on the untreated trees, the leaves started to
fall by the 10th of November, the leaves on the treated
trees continued to be green and held onto the twigs.
These latter turned brown through the winter, but never­
theless most of the leaves with their petioles stayed
firm, with the result that as late as the 20th of March,
the treated trees could be easily distinguished from all
the rest by the brown leaves sticking out all over the
tree.

While subsequently, due to winds, most of the

-33blades were torn off it was stil 1 possible to see here
and there full brown leaves, and portions of brown leaves
holding on with the petioles, as shown in the photograph
taken on the 34th of April, 1948 (Plate 8).

Still later,

almost all through the succeeding summer, one could
observe most of the petidle-stubs tight on the twigs,' a
specimen of which is shown in the photograph (Plate 6).
Thus the formation of an abscission layer was entirely
prevented by the spray.

Previous-season Fruits
The abscission of the few stray fruits that were
ripening late on the tree, at the time of application of
the spray, was affected also and'long after the fleshy
portion of the fruit decayed and dried, the pedicel with
the stone attached continued to stay firmly on the twigs.
Here also the normal process of abscission was thus
completely prevented as a result of treatment.

Flowers and Flower-parts
In the case of flowers that opened in spring, where
fertilisation had taken place, the petals were slow in
dropping off.

In the case of flowers where pollination

had not taken place, the flowers stayed on the twigs.
They subsequently dried up but still held on.

Plate 6

shows the photograph of such an example, taken on the
16th of July.

It is evident from this photograph that

every part of the flower - the calyx, the petals, the
stamens and the pistil - were still intact.

When the

trees were observed on the 15th of December, 1348,
the dried-up flowers were still there.

Here again the

formation of an abscission layer was completely pre­
vented.

In the case of fruits, with aborted ovules, -they

took on color early and continued to stay on the twigs.

Mature Fruit
The abscission of the fruit was also noticeably
delayed, and the fruit held on for weeks after the har­
vest time, indicating a continuity of effect of the plant
growth regulators for more than ten months from the time
of application.

The Style
The style of the developing fruit on the treated
trees persisted not only -for an abnormally long period,
but a small portion of it remained attached to the mature
fruit, thus accentuating the pointedness of the fruit.
Delayed abscission of style as a result of treatment with
plant growth regulators has been reported by Elmsweller
and Stewart (30), Hamner, Schomer and Marth (40), Zimmerman

-35and Hitchcock (110) and Stewart and Klotz (88), among
others.

Discussion
The ability of plant "hormones" in varying degrees
of effectiveness to prevent or delay abscission of flowers,
fruits and leaves has been demonstrated by numerous
workers (44, 34, 110, 111, 88, 70).

But what deserves

particular attention in this respect in our experiments
is the fact that there was no plant organ, which normally
undergoes abscission in some stage or other, that did not
show effective response to the treatment.

That there are

anatomical differences in the process of abscission of
different plant parts has been conceded (59, SO, 55). and
it may be pointed out that under conditions of this ex­
periment, the difference in method of abscission has not
stood in the way of effective action of the plant growth
substances.
Literature reveals that plant growth regulators have
acted consistently in this respect not only on different .
parts of the same plant, but on a variety of plants in­
volving different types of abscission.

To mention a few,

Gardner, Marth and Batjer (33) reported delayed abscission
of mature fruits of apples; Milbrach and Hartman (61)

-36that of leaves of holly; Kraus and Mitchell (52) that of
treated internodes of decapitated beans; Eeal and Whiting
(13) that of treated internode of decapitated Mirabilis
.jalapa; Mitchell and Stewart (68) that of cotyledons from
treated bean plants; Weaver (100) that of primary leaves
of red kidney beans; Zimmerman and Hitchcock (110) that of
petals., stamens and styles of tomatoes; Stewart and Klots
(88) that of leaves and blossoms of oranges; Nixon and
Gardner (77) that of perianth and fruits of dates.
In spite of all this evidence of the potential
capacity of plant growth regulators to delay or prevent
abscission, or in other words, to arrest senescence, a
certain opinion has been held popularly but on insufficient
data, by some workers (33, 23, 33) that when a plant
growth regulator has not proved effective in preventing
or delaying abscission, it is because of a difference in
type of abscission.

But a. review of a large amount of

literature in the field of plant growth regulators, in­
dicates that while there may be some truth in it, the
problem is not as simple of explanation, but that it is
allied to the problem that is faced in the whole field
of plant "hormones", in attempting to explain the differ­
ential reaction of the various tissues of the same organ,
the differential varietal responses, the differential
responses on account of changes in external environment

-

37-

or the selectivity of 2,4-dichlorophenoxyacetic acid as
a herbicide.

It seems to be more related to the funda­

mental problem of the variable and unknown state of
protoplasm, the substrate, at the time of application
of the causal factor, the plant growth regulator.

3. Effects on the Opening of Floral and Vegetative Buds

Floral Buds of Sour Cherry
Some general but continuous observations from the
time the tree was sprayed, on this aspect were possible
with the sour cherry but was not possible with the sweet
cherry, because of the fact that the buds in treated
sweet cherry tree were very severely injured and during
the winter, almost every bud that was examined from this
tree was discolored and showed signs of injury.

Growth of Buds up to the Bloom Stage.
The observations on sour cherry buds at frequent
intervals showed that as far as external evidence of size
was concerned, the untreated buds showed slightly larger
size as the first few weeks went by and they were some­
what noticeably larger when examined on the ,31st of
December, 1947.

Between this date and the 2nd of April,

-381948, the treated buds had almost caught

up and very-

little difference in size could be noticed between the
treated and the control.
But when a subsequent examination was made on the
17th of April, it was evident that while the control
buds had advanced farther towards subsequent opening,
though still closed, actually as far as the size of the
buds was concerned, many of the treated feuds were defin­
itely larger than the control, both in length and width.
Seven days later, i.e. on the 24th of April, 1948, such
a size comparison was no longer possible,

since in the

untreated tree, the pedicels had elongated and the indi­
vidual flowers still closed, had emerged out of the bracts
while in the case of the treated tree, m a n y buds had
swollen further but no such elongation of the pedicels
had taken place.

Please, see Plate 8 for

After another interval of six days,

comparison.
i.e. on the 30th

of April, 1948, in many flower-buds of t h e treated tree,
the pedicels had elongated with the flowers still closed,
a stage comparable to the buds of the control, 6 days
earlier.

In making observations of the flower-buds of

this comparable stage, it was noted that

those of the

treated tree were again much longer and feroader than the
buds of the untreated.

At this stage, i n both the treated

-39and the untreated, the length of pedicels was variable
and was not a factor for comparison.

Opening of Buds.
Day by day observations showed that the untreated
tree attained its full bloom on the 30th of April.

On

this date, flowers in the treated tree were still closed
without exception.

This w&s evidence by itself of the

effect of treatment in delaying bloom.

Further daily

observations revealed that the upper levels of the tree
were the earliest to bloom, and in a relatively uniform
manner.

The maximum flowering in these relatively healthy

portions of the tree was attained on the 7th of May,
indicating a definite delay of 7 days, as a direct response
to treatment.
In the rest of the tree, the story was different.
The behavior of blossoming was erratic.

The flowers were

opening here, and there at irregular intervals.

There

was definitely an interfering factor of injury but there
were evidences, however, that the delay in these cases
was due to a combination of factors of effect of injury
and effect traceable directly to the treatment, as the
formative pattern of the flowers subsequent to the opening
proved in almost all the flowers.

In these portions of

-40the tree, flowers were seen opening, as late as. the 13th
of June, 44 days after the control had recorded full bloom.

Floral Buds of Sweet Cherry
The untreated sweet cherry tree attained full bloom
on the 28th of April.

Since, as mentioned before, the

treated tree was severely injured, there was no possibility
of demarcation between the injured and the uninjured por­
tions, with the result that all that could be said was that
there was definitely a delay in opening of flowers, and
that the first fev^r flowers opened 9 days later than the
untreated and subsequently, the flowers continued to open
at irregular intervals here and there.

On the. 4th of June,

1948, 37 days after the date of full bloom of the untreated
tree, a few flowers were still opening.

As late as the

19th of -July, two flowers were noted opening out.

In sweet

cherries as in portions of the sour cherry tree, the delay
in blossoming was due to a combination of effects of injury
and treatment, as the formative patterns of flowers and
fruits produced subsequently showed.

-41Leaf-buds
General Observations.
The effect of the treatment in retarding the opening
of the vegetative buds was even more severe.

There was

not only delay in the opening of the vegetative buds; there
were buds that were killed completely as mentioned under
"Injury".

There was curvature and twisting of leaves as

they emerged from the buds (plate 5).

In some severe

cases of affection, the leaves as they emerged were chlorotic to some extent, and had mottled appearance.

On account

of these differences between the untreated and treated
trees, the comparable appearances of the trees v/ere also
different.
Sour Cherry.
On the 3rd of May, 1948, the untreated sour cherry
was almost fully clothed with foliage and in contrast,
the treated tree was almost bare of leaves, with a very
negligible number of opened vegetative buds.

It was

only on' the 28th of May, that the tips of branches and
the upper levels of the treated tree were noticed to be
covered with leaves, indicating a delay of at least 25
days in the opening of vegetative buds of the sour cherry.
From this date onwards, the opening of the buds in the

-42other portions of the treated tree was by fits and starts
and was prolonged by an indefinite period.

For instance,

as late as the 10th of October, 1948, 3 buds were noticed
opening.

Sweet Cherry.
In the treated sweet, cherry, the retardation effect
and the irregularity of opening of vegetative buds was
even more severe.

The maximum foliation had occurred

by the 30th of April, 194S, in the untreated tree, and
it was not until the 28th of May that•the tips of branches
and the topmost levels of the treated tree showed foli­
ation.

The opening of vegetative buds on this tree was

noticed as. late as the 19th of July, 1948, and the reason
why no further opening was noticed was obviously due to
the fact.that the rest of the buds had been killed on
the treated tree.
Thus, in comparison to the floral buds, the retard­
ation effect and the irregularity, of opening of vegetative
buds was even more severe.

Discussion
The whole question of delayed foliation and delayed
blossoming is related to the subject of bud-inhibition,

—43—
the relation between which and the growth regulators
has been a subject of inquiry by several workers (for
example, 90, 103, 53, 68).

Observations on the extent

of delay of flowering have been made by Krone and
Hamner (53) who reported a delay in gladiolii of about
two weeks as a result of the soil application of 3,4-D
at 10 to. 20 pounds per acre, by Winklepeck (107) who
reported a delay of 11 days in peach as a result of
aqueous spray of naphthaleneacetic acid at the rate of
125 mg. per liter prior to blossoming and by Hitchcock
and Zimmerman (46) who reported a delay of a few days
to fourteen days in sour cherry depending on the concen­
tration and time of applying potassium naphthaleneacetate
summer sprays.

The inhibition effect on vegetative buds

has been studied extensively (19, 37, 91).
.While in all this literature quoted, a direct response
of delay in opening of buds was reported, there are a few
workers (57, 63) who considered any delay obtained as
being associated with injury and not a direct response to
treatment.

In our experiments, the delay in almost all

cases was to some extent at least due to the treatment
as shown by formative responses but the greater the injury,
the greater was the additional delay.

-444. Formative Effects and Histological Studies
The Fruit
Under these studies, the fruit is taken up first,
because of convenience, its economic importance and
because the most notable modifications are found in it,
as a result of treatment.

Comparative Description of the Treated Fruit.
Since the pattern of changes was almost identical in
both cases of sweet cherry and sour cherry, the descrip­
tion applies to both unless there is a distinctive point
to be made or a distinctive measurement to be stated.
The original measurements of the treated and untreated
fruits are mentioned in Tables 1 and 2.

The description

given here is to emphasize the changes in the morphology
of the fruit, also from a horticultural point of view,
compared to the untreated fruits.

Plates 11 and 12 show

the photographs of comparative appearances of the fruits
of the untreated and treated sour cherry and sweet cherry
respectively.
Hanging Quality:- Fruits of the treated cherry held
tenaciously to the tree.

In many cases, it was. not

possible to harvest the fruit by stripping it from the
tree without the stern.

If the fruit was mature enough

at the time of harvest, attempts to pick the fruit would

. -45Table 1. Measurements of Fruit of Sour Cherry*
Untreated
Size - length in mm.
diameter in mm.

Treated

16.9
19.4

20.1
19.0

weight in gm.

3.7

4.3

Volume in ml. water displacement

4.1

4.2

'Width of receptacle in mm..

3.2

6.5

25^9
0.8

22.1
2.1

Stone - length in mm.
’width in mm.
thickness in mm.

9.4
8.7
6.7

11.7
8,2
7.0

Volume in ml. water displacement

0.27

Weight in gm.

0.4

Stem - length in mm.
thickness in mm.

Thickness of stony pericarp in mm.
0.8
*Values given are from average of 100 fruits.

0.32
.

0.9
.1.6

ordinarily result in the soft flesh tearing away, leaving
the pit and stem on the tree.

A closer examination re­

vealed that it was because the pit and the vascular system
were firmly attached to each other.

Observations on the

vascular system will be mentioned later.

In fact, even

■after the fruits were over-ripe and rotting, it would be
hanging on to the tree in contrast to the normally easier
dropping of the fruits of the control trees.
Sloe:- By water displacement method, the average
volume of the treated fruits was almost identical with

-46Table 3. Measurements of Fruit of Sweet Cherry*
Untreated
Size - length in mm.
diameter in mm.

Treated

18.4
31.9

22.1
19.8

4.9

5.8

4.8.

4.7

3.5

9.1

Stem - length in mm.
thickness in mm.

33.0
1.2

4-5.1
2.1

Stone - length in mm.
width in mm.
thickness in mm.

9.6
8.8
6.9

11.3
9.8
8.9

Volume in ml. water displacement

0.50

0.67

Veight in gm.

0.2

0.4

1.1

2.3

height in gm.
Volume in ml.
UW

water displacement

idth of receptacle in mm.

Thickness of stony pericarp

inmm.

♦Values given arefrom average of 100 fruits.
that of the untreated fruits, within about 2 per cent.
This came as a surprise, since the differing shapes of
the tree,ted and- untreated fruits gave no indication of
that being: the case.
Weight:- When the same set of fruits that were used
for measurement of size above were used for weight measure­
ment, it revealed that the treated fruits showed definite
increase in weight, over the untreated.

The sour cherry

showed 16.2 oer cent increase and the sweet cherry 18.4

-47per cent.

Increase of weight of fruit as a result of

application of plant growth regulators has been reported
for example, in tomatoes (40), in blackberry fruit (58)
and pineapple (28).
Shape:- One of the most evident effects of the
treatment was on the shape of the fruit.

The fruits of

the treated: trees were elongate and broader near the
stem end and tapering: down to a point at the apex, usually
with a small persisting portion of the style.

This descrip

tion was broadly true of almost all the fruits irrespective
of from which portion of the treated tree they came.

The

only variation in shape that was noticeable was the more
regular or symmetrical shape of the fruits coming from the
healthier portions of the tree and the lack of that regu­
larity and symmetry, increasing with the injury to the tree
All this is in contrast to the fairly round and regular
shape of the fruits from the untreated tree.
Some measurements of length and diameter of the fruits
were indicative of the pattern.

The length of the treated

fruits was 18.9 and 20.1 per cent higher .in the sour and
sweet cherry respectively, over the untreated.

The dia­

meter was 2.1 and 9.6 per cent less respectively, over the
untreated.

A length/diameter ratio is even more indica­

tive of the elongation aspect of the fruit and such a
ratio is higher in the treated fruits.

-48Suture:- The suture of the treated fruits was more
distinct.
Apex:- The treated fruit had a well-pointed apex,
sometimes with a small nipple-like protuberance as pre­
viously mentioned.

In contrast, in the untreated fruit,

it was almost absent, but with a very indistinct blunt
point at the tip.
Receptacle:- In the untreated fruits, the receptacle
is almost dry and shrivelled to the size of the pedicel,
but in the treated fruit, the receptacle is often green,
fleshy and spread out in more or less a circle with an
increase in diameter of 103.1 and 160.0 per cent in the
sour and sweet cherry respectively, over the untreated.
Marth and Meader (42) reported that the receptacle
of blackberry was stimulated by application of growth
regulators at time of flowering.
Stem or Pedicel:- The treated pedicels of sour and
sweet cherry showed an increase in thickness of 162.3 and
75.0 per cent respectively over the untreated.

They were also

firmer to the touch and this firmness was most noticeable at
the time of taking freehand sections for histological studies.
Increased development of the pedicel has been reported br­
others.

Among them, Stewart and E’
oeling (87) reported in­

creased thickness of pedicel and secure attachment of

lemon fruit when 5-year-old lemon trees were sprayed with
2,4-dichlorophenoxyacetic acid in September.

Clark and

Kerns (43) found that high concentrations of naphthaleneacetic acid resulted in larger and.thicker peduncles and
difficulty was experienced in separating the fruits from
the peduncles at the time of picking.
Color of the Fruit:- The treated fruits were defin­
itely lighter in color than the untreated fruits, and
this lightness of color was more accentuated in the case
of the sweet cherry.

Decrease in color as a result of

application of growth regulators has been reported in
tomato (21).
The Skin:- The skin of the treated fruit was pronoun­
cedly thicker, tougher, more astringent and more adherent.
Stewart and Klotz(44) reported that.as a result of 2,4dichlorophenoxyacetic, acid application, the rind of oranges
became several times thicker than the normal.
The Flesh:- In the treated fruits the flesh was lighter
colored and the resulting juice was also lighter colored.
Regarding texture, since in the treated fruit, there was
ls.ck of extension of the vascular system into the flesh,,
the flesh seemed finer to the touch than in the control
fruit where, because of the greater extension of the vas­
cular system into the flesh, it seemed to be coarser to
touch.

-50Taste and Flavor:- The flavor of the treated fruit
was relatively poor and taste relatively insipid and less
sweet.
The Stone:- The stone in the treated cherry had elon­
gate and pointed shape like the fruit and the surface rough
and variously ridged, compared to a roundish shape and an
almost smooth surface of the stone in untreated fruit.
As far as adherence of the stone to the flesh was con­
cerned, as explained previously, it was easy to slip off
the flesh from the stone with the vascular system sticking
to the stone in the case of the treated fruits, whereas
this was not possible with the untreated fruits.
Comparative measurements of the three dimensions of
the stone revealed that there was a closer correlation
between the shape of the fruit and. the shape of the stone
in the case of the treated fruits than in the case of the
untreated fruits.
The size .of the stone as a result of treatment showed
by water displacement method 18.5 and 34.0 per cent increase
the weight 125.0 and 100.0 per cent increase; and the
thickness of the stony pericarp 100.0 and 109.1 per cent
increase, respectively over the untreated.
These figures are indicative of an undue development
of the stone, in relation to the rest of the fruit.

-51Development of the Fruit.
A clear picture of what we have seen of the large
number of modifications in the mature fruit as a result of
the application of spray of 2,4-dichloropheno.xyacetic acid
and naphthaleneacetic acid csn only be obtained by going
through the development of the fruit, at the different
stages of growth.
The observations made are detailed below;
The Shape of the Fruit (some developmental observa­
tions);— At the time when the flowers are just open, re­
garding the shape of the ovary, close observation reveals
no very significant differences between the treated and the
untreated.

But there is a factor which creates an impression

of a difference at first glance.

The style of the treated

pistil' is much enlarged in sice, and often it tapers at
its bs.se indistinctly into the tip of the ovary and the
ovary itself is not much thicker at this stage than the
base of the enlarged style and all this contributes to a
different appearance of the ovary.

In fact, however, the

ovaries in the flowers of both the treated and untreated are
elongate and more or less cylindrical.

The shape is very

distinct in the case of the ovary of the untreated because
of the distinctness with which the style separates off
from the outline of the ovary.

At this stage, there is

no relationship to the ultimate shape of the mature fruit.,

— 53—
particularly in the case of the untreated cherry where
normally the shape is more or less round.

In this

respect, perhaps, the ovary of the treated cherry is
slightly more akin to the final shape of its mature fruit,
which is elongate, but in other respects the proportions
of dimensions are different.

When observations were made

of the fruits of untreated sour cherry on May 31, 1948,
they were still cylindrical, with the tip rounded off and
with a little portion of the style attached.

Before 7

days more elapsed, i.e. by the 38th of May, the fruits had
slightly enlarged breadthwise.

From then onward, every,

external.evidence of growth was more and more towards the
ultimate rounded shape of the fruit.

In the case of the

fruit of the treated sour cherry, within about 15 days of
fruit-set, the fruits were more like the ultimate shape
of the fruit.

Here again, the persistent style and the

original elongate nature which does^not change much is
responsible for this distinguishing feature.
The pattern of behavior in the matter of shape was
the same in both the cherries.
A discussion of what factors contribute .to the modi­
fication of shape will be made later.
Size:- Here again, when the flower is just open, there
is very little distinction between the ovaries of the

-53treated and untreated trees.

Yfe have already noted the

little difference in size of the mature fruits also.

A

discussion of the factors that contribute to the main­
tenance of size, irrespective of treatment will be made
later.

Histological Observations of the Developing Fruit.
General Observations:- The observations made here
and the data quoted in their support relate to sour
cherry.

This is. because, for comparison and proper in­

terpretation, the work of Tukey and Young (98) is
available.

But examination of sweet cherry revealed broad­

ly the same pattern.
According to Tukey and Young (98), the ovary wall
consists of three principal tissues, the inner and outer
epidermis, inner and outer stony pericarp, and the
fleshy pericarp.

The fleshy pericarp in turn consists

of an innermost layer of small thin-walled parenchyma,
a middle region of large thin-walled parenchyma and an
outer or hypodermal layer of collenchyma.

The fleshy

and stony pericarp are derived each from distinct group
of cells.

The developmental behavior of the fleshy and

stony pericarps is somewhat different.

In the three char­

acteristic stages of development mentioned under Tukey'
(95) in "Review of Literature", while in Stage I both

-54the pericarps multiply and enlarge, in Stage II greater
activity is in the stony pericarp, where there is con­
tinued thickening of cell-walls and hardening and there
is less activity in the fleshy pericarp, where the en­
largement of cells is. very slight, and in Stage III there
is almost cessation of activity in the stony pericarp but
in the fleshy pericarp, there is greatest activity with
increase in size of cells, radial elongation of cells
towards the inner regions of fleshy pericarp and tangential
elongation of the hypodermal cells.
Examination of series of cross-sections of the devel­
oping fruit from the full bloom stage revealed that in the
broad pattern of development, the treated fruit behaves
just in the same manner as described by Tukey and Young
(98).

But there are certain features which stand distinct

as a consistent result of the treatment.

To indicate

these features, detailed diagrams have been made at
certain relevant stages (Plates 14, 15, 16).
Figure 1 of Plate 14 is a cross-section of the fruits
in the early part of Stage II, when the first rapid devel­
opment of pericarp has been completed and thickening and
hardening of the cell walls of stony pericarp has commen­
ced.

There are certain conspicuous differences which

become immediately evident, particularly in the vascular
system and the stony pericarp.

The Vascular System:- As shown in the diagram, the
relative position of the vascular system has completely
changed.

According to Tukey and Young (98) and as shown

in the drawing (Plate 14, Fig. IB), the vascular system
normally exists as a ring of vascular bundles,

generally

18 to 30 in number and extend through the fleshy pericarp.
In.the words of Tukey and Young (98), "the vascular
system, moreover, is extended progressively throughout
the tissue as the fruit develops, largely by transverse
divergence of small bundles from the main bundles......
At maturity the vascular bundles ramify throughout the
fleshy pericarp to give a skeleton network of conductive■
tissue.,f
In contrast to this, in the case of fruit of the treat­
ed sour cherry, the relative position of the vascular system
has shifted from about the center of the fleshy pericarp
to close to the outer layer of the stony pericarp.

But

for a few interruptions, it hugs close to the outer edge
of the stony pericarp.

There has also been a great -

amount of proliferation of the vascular tissues resulting
in an undue thickness and coalescence of bundles giving
an appearance of one solid mass of r^scular tissue with
very few gaps in-between, in contrast to the "ring of
vascular bundle’s" in the fruit of the untreated cherry.
Examination of the ovary, just after the flower opened

-56frora the bud, revealed, that this pattern of vascular
system had already been established prior to opening.
Moreover, this pattern appeared even more accentuated
when mature fruits were examined.

Plate 14, Fig. 2

shows a part of cross-section through epidermis and
fleshy pericarp extending to almost the outside of stony
pericarp.

The remarkable proliferation of the vascular

tissue into a thick mass of network is shown out against
the moderate size of the vascular tissues in the untreated
mature fruit.

The condition and extent of the vascular

system is most impressive in opening up the fruit by hand.
The outer portion of the flesh comes off free from, the
stony, pericarp and. its strong vascular tissues, adhering
to and enveloping the stony pericarp.
Stony Pericarp:- The next important difference lies
in the stony pericarp.

There are evidences of prolifer­

ation of the tissues of the stony pericarp resulting in
a greater thickness of the stony pericarp.

Its ultimate

thickness being more than twice the normal has already
been mentioned.

The proliferation is so irregular that

the margin of the outer layer of stony pericarp takes on
an uneven, wavy, and rough outline.

The appearance remains

so throughout the development of the fruit so that finally
when a' mature fruit is opened, and the clinging vascular
tissues are removed, and the stone is wiped dry, the diff—

-57erence in appearance of the stone of treated cherry from
that of the untreated is remarkable, the surface of the
untreated being relatively smooth, in contrast to the
roughness of surface of that of the treated, as shown in
Plate 13.

The accentuation of these rough markings on

the sweet cherry stone is well seen in the photograph.
It is obvious that the irregularly outlining vascular
system clinging to the stony pericarp region even prior
to opening of the flower-bud has exerted also a retarding
influence on the expansion of the cells of the stony peri­
carp at the points in contact and has thus contributed to
the irregular markings on the stone of the treated cherry.
Part of the markings may also represent the impression left
by the clinging vascular tissues early in the development
of the .stony pericarp, when the cells were still pliable.

Cellular Details,
Stage II:- Tukey and. Young (98) have also reported
enough information on the cell-size, shape and thickness
of cell-walls, etc., of the different tissues of the sour
cherry at different stages of growth of the fruit.

Early

part of Stage II marks, an important stage in development
and due to the suppleness of the stony pericarp for taking
sections of the fruit, it has advantage in detailed obser-

-58-

vat ions of the cells.

Drawings in Plate 15 represent

portions of epidermis, hypodermis, fleshy pericarp, and
outer and inner stony pericarp.

As shown in the diagram

at this stage, the cells of the epidermis and hypodermal
layer do not show much difference in size or shape, between
the treated and the untreated.

In the case of the cells

of the thin-walled parenchyma of the fleshy pericarp, there
is very little difference as far as size is concerned, but
regarding shape, the cells of the untreated are more regu­
lar than those of the treated.

It appears as though, in

the treated, the enlargement of these cells prior to
Stage II has been rather irregular, resulting in some
amount of intercellular spaces.
In the case

ofthe

the individual cells of

outer layer of the stony pericarp,
the treated are slightly larger,

but the amount of thickening at this stage appears to be
more or less the same, and there is very little difference
in shape,
Regarding the inner layer of the stony pericarp, the
shape of the majority of cells, and the kind of juxta­
position of individual cells, dovetailing into each other,
are the same in both treated and untreated.

But there

a,gain seems to be certain irregularity in expansion of
individual cells

of

thetreated.

Stege III:-

In

thisconnection,it .must be remembered that

-59Stage II of which we have reported above, represents,
according to Tukey and Young (98), the culmination of a
period in which the cell— enlargement of the fleshy peri­
carp had not progressed much.

It is Stage III in which

a rapid enlargement occurs with certain changes in shape
of cells in the different regions of the fleshy pericarp.
To ascertain, therefore, in what manner this aspect of
development has been affected by treatment, tissues were
examined from the cross-section of the mature fruit and
the results are shown in Plate 16.

It shows the following

features:
While the tangential enlargement of the epidermal
cells does not differ much, that of the hypodermal cells
has been conspicuously greater than that of the untreated.
In fact, during Stage III, the growth of the individual
cells of the hypodermis in the treated fruit has all
around been greater than that of the untreated fruit.
The result of all this with regard to the hypodermis is
reflected in the additional thickness of the skin noticed
in the treated fruit. '
In examining the size and shape of .cells involved in
the final swell of fleshy pericarp in radial direction,
the pattern is similar to that mentioned by Tukey and
Young (98), irrespective of treatment, viz. that the
cells next to the hypodermal layer are roundish, followed
by oval shape indicating beginning of radial elongation

-60—
followed subsequently by a decided radial elongation in
the inner region.

As far as the individual size of cells

in cross-section is concerned, there are only slight
differences.

The Pedicel
General Observations.
A study of certain histological aspects of the pedicel
is essential for the following reasons.

It is important

as an intermediary between the branch and the fruit,
whose nature of conductive tissues to a large extent
decides the type of nutrition to the fruit.

It plays an

important role in the abscission phenomena connected with
the fruit.

Besides all this, we have previouly described

certain modifications in the pedicel as a result of treat­
ment, which need correlation with a study of the internal
structure.

Plate 17 shows the cross-sections of the

treated and untreated pedicel at the mature stage of the
fruit.

In .examining the different zones, there has been

increase in thickness of every zone, the epidermis, the
cortex, the fiber-sheath, the vascular cylinder, and
the pith.

-61Fiber Cells:- The fiber-sheath, which by virtue of its
position may be called as pericycle fibers, is shown as
continuous in the diagram for the sake of convenience, but
it is actually discontinuous, and consists of groups of fiber
cells with gaps in between.

The fiber-sheath of the treat­

ed is more continuous, or in other words, the gap between
groups of cells is relatively smaller and each group is
individually larger and more extensive.
the differences in individual cells.

Plate 19 shows

In the untrea.ted,

the cell-wall is so thick that there is hardly any vacuole
left, while in the treated there is relatively less amount
of thickening, but fair enough to contribute to the strength
of the individual cells.

The main purpose of fibers cells

is to contribute to strength of the tissue, and this
difference in thickening of cell-wall is of minor importance
from this point of view, since in the case of the tresited.
pedicel, the largeness of individual cells, the largeness
of individual groups and a greater continuity of fibersheath all contribute to greater strength and. firmness
of the pedicel, which has been observed in handling the
pedicel, even without examining the tissues inside.
The Vascular System:- Of the other tissues in general,
the vascular system again, as in the fruit, is of striking
importance.

If the radial width of the vascular region

is taken into account, (See Plate 17, HTandF) that of the

-62treated pedicel is more than twice that of the control.
What this means in actual total area of the vascular tissues
in cross-section and in the ultimate amount of vascular
tissues insid.e the pedicel is of great significance, in
the conduction of nutrients from the stem into the fruit.
In a closer examination of the phloem region and
the xylera region, in several sections, it was consistently
clear that the phloem zone exceeded in its radial width
over the xylern, in the case of the treated, while it was
the reverse in the case of the untreated pedicel.

Besides

this, a detailed examination showed that not only has
there been during the development of the pedicel, a greater
activity of the phloem but also to some extent an inhibition
of the activity of xylem, of which we will mention in a
little more detail in dealing with the shoot growth in
spring and summer, during the period of our experiment.
While this was the condition in the vascular system
of the mature pedicel, examination of the pedicel just
when the flower was open revealed generally a fluted shape
of the vascular cylinder in cross-section, which developed
later into a. more uniform thickness, as shown in the
mature pedicel.

At the time of flower opening, in the

treated cherry, the number of ridges in the fluted shape
of the vascular cylinder generally exceeded those of
the untreated, the former being 10 to 12 and the latter

-636 to 8.

It v/as sometimes noticed that, at this stage,

the bundles might be distinguished as individual bundles
with very little gap particularly towards the center.
At this stage of flower-opening, there already has
arisen a remarkable difference in size of the vascular
tissue.

Plate 18 shows a camera lucida drawing of

cross-sections of comparable portions of the vascular
system.

In the treated, the radial width of the vascular

area is twice that of the untreated and the tangential
width about one and one-half times.

Calculations'of

relative areas in cross-section indicate the vascular
system being 4 to 5 times larger at this stage due to
treatment.
A comparison also at this stage between the relative'
proportions of phloem and xylem indicate that in both
treated and untreated, the xylem elements seem to be
greater in content than the phloem, but the greater activ­
ity of the cambium layer is already evident, as repre­
sented by a wider.band as indicated in Plate 18.
The comparatively greater development of the vas­
cular system as a result of treatment, accompanied with
certain other important differences in details becomes
even more impressive, in watching subsequent development
of the pedicel.

For instance, Plate 19 represents camera

lucida drawings of the same comparable portions of vas­
cular tissue as seen at the end of 3 weeks after full
bloom.

In comparing these drawings with those of Plate

18, certain points stand out clearly.

In the untreated,

during this period, the vascular tissue has doubled itself
both radially and tangentially.

But even after three

weeks of development, it has not caught up, however, with
the radial development that the tissue of the treated
had attained three weeks earlier.
Besides this, the measurement of the radial width
shows that in the untreated, the development has been
more towards greater development of xylem than of phloem.
In the case of the treated, the tendency of develop­
ment is clear.

While the radial width of the xylem has

changed very little, the average width of the phloem has
almost doubled.

What was a ridged cylinder is being

straightened out- into a more uniformly thickened cylinder
and in doing so, the phloem is tending to expand farther
than the xylem.

The ultimate result, however, of this

relatively higher.development of the phloem over the
xylem in the development of the vascular tissue, as a
result of treatment is most clearly brought out in the
examination of the cross-section of the pedicel, when the
fruit is.mature, -about which we have already spoken before
Thus, as a result of treatment, a more expansive

-65development of the vascular system takes place in the
pedicel, as we have already seen in the fruit.

We have

also gone one step further in noticing that there is a '
relatively higher activity in the phloem than in the
xylem.

From all this, it would be reasonable to assume

that the most important contributory cause for the
strength of the pedicel of the sprayed tree is its well
developed vascular system and among other important
causes is the more extensive pericycle fibers encircling
the pedicel.

The importance also of the development of

phloem in its nutrition role cannot be overlooked.
Plate 19 also shows a conspicuously wide band of cambium
zone in the pedicel of the treated.

In fact,, under the

microscope, it was in the nature of a multilayered band,
giving the impression of a ladder-like structure and
giving indications of delay in differentiation of deriva­
tives.
Other Tissues:- Plate 30 shows the camera lucida
drawings of representative cells of the tissues other than
the vascular and fiber.

The drawings show the obvious

differences and similarities.

There were clear differ­

ences in the cuticular structure.

It seems as though

because of a greater length of the epidermis, forming
the circumference of the treated pedicel, the cuticle
gets flattened out (See Plate' 20).

-66-

In the cells of the epidermis, the collenchyma and
the parenchyma cells of the cortex, in the treated, there
has been cell-enlargement by about 50 per cent, on the
average, over the untreated, but no change in shape from
the untreated.

Further development of the pedicel showed

even more increased enlargement of the cells of these
tissues.

It was evident from observations throughout

the development of the pedicel that the increase in size
of these regions, epidermis, collenchyma, and the cortex
in the case of the treated, was almost solely on account
of the increase in size of the cells.
Examination of the cells of the pith did not show
much difference in size at the time of opening of the
flower but in further development showed enlargement in
size, contributing its quota to increased thickness of
the pith, in the treated pedicel.
In calculating the increase in size of the cells due
to treatment, it was found to vary over the untreated from
60 to 100 per cent in the case of pith and cortex and 50
per cent in the case of epidermal and collenchyraacells,
during the whole course of development.

Other Parts of the Flower
Having dealt with the ovary, its development to a
mature fruit and with the pedicel., it is relevant at this

-67juncture, to note observations on the other accessary parts
of the flower.

The Receptacle.
The larger size of the flower buds of the treated
cherry, noticed prior to opening and mentioned before in
the studies of retardation of opening of floral buds, was
mostly on account of a fleshier receptacle.

Thus from the

very early stages upto fruit maturity, the more prominent
receptacle is one of the consistent responses to treat­
ment.

Its spread in the mature fruit compared to the

untreated has been described under the comparative descrip­
tion of the treated fruit.

The Calyx.
The first difference that is noticed between open
flowers of treated and untreated cherry is the difference
in angle at which the calyx lobes are bent.

Normally in

an open flower, the lobes are completely reflexed, so that
the lobes are bent parallel'to the axis while in the
flower of the treated cherry, it was very usual to find
varying degrees of bending, some of the flowers having
the lobes either at right angles to the axis or even bent
slightly in the opposite direction to the normal or, in
other words, tending to bend towards the axis.,(See Plate 9)

-68This aspect in the calyx is emphasized, because it is in
consonance with a tendency observed for certain types of
organs of the plant to bend in the same direction.
Besides this feature, the lobes of the calyx in the
treated were thicker and narrower with a characteristic
triangular shape, a rels.tively acute tip, more prominent,
more numerous and deeper serrations, and more conspicuous
venation, than in the untreated.

The Corolla.
A little more study of corolla than of the calyx was
involved, because of the strikingly different appearances
of the petals as a result of treatment, even at first
glance.
The change in shape was the most easily noticeable.
The petal had become elongate and narrow compared to an
almost roundish shape of the petal. (See Plates 9 and 10).
It was usual that the increase in length was by 20 per
cent and the decrease in width by 33 per cent compared to
the dimensions of the untreated flower.
The thick, leathery texture with a stiffness of the
petal was again most striking.

The increased thickness

consisted mostly of the enlargement of cells, of inter­
cellular spaces and of the vascular tissues, which latter
contributed also to the stiffness of the petal.

In die-

-69section of the flower, consequently, it was easier to
handle compared to the petal of tire untreated cherry which
was comparatively delicate, thin and easily folded on
itself.

It was also not so easy to pull out the petal of

the treated cherry.
The very thick and prominent venation of the petal
of the treated cherry was even more striking.

A detailed

drawing of the venation has been made in Plate 21,

This

is in many ways comparable to the character of the vas­
cular system in the fruit, particularly in its massiness,
and.its lack of tendency to ramify.

The finer ramifica­

tions as seen in the flower of.the untreated cherry are
almost lacking in the treated.
A surface view of the epidermal cells indicated cer­
tain differences and a group of such cells have been
drawn (Plate 21).

The waviness of the margin of the cells

of the untreated petal becomes more or less levelled up
as a result of treatment and the distinct incree.se in
size is also indiccted.

It is a case of longitudinal

stretching.
Lastly,-another important feature with regard to
the petal is again the tendency to incurve or to bend
towards the axis, so clearly seen in Plates 9 and 10.

-70The Stamens.
The following features were noticed as a result of
treatment.
The length of the stamens was variable just as in the
case of the normal flower, but the average length was
often higher, particularly in the case of the sweet cherry,
by 20 per cent (Plate 10).
There was a decided increase in thickness of the
filaments, often being twice thicker than the normal fila­
ment.
10).

This was most prominent in the sweet cherry (Plate
The increased thickness was mostly on account of

enlargement of individual cells and increased vascular
material.

This was reflected also in handling of the

stamens in dissection, being firmer and stiffer and
easier to handle.
The anthers were noticeably larger (Plate 10) and
they had s. characteristic heart-shape, pointed at tip,
compared to the roundish shape of the anthers of the
normal flower.
The stamens, again like the petals, had a tendency
to incurve or bend towards the axis.
The viability of pollen of the flowers was tested by
germinating it in sugar and agar media and treatment was
not found to affect the normal viability of the pollen.

-71—
The Pistil.
The ovary and the development of f ru.it have been
dealt with above.
The increased thickness of style, as well as its per­
sisting quality as a result of treatment, has also been
mentioned.
The stigma, was also slightly larger, but more irregular
in shape, as a result of treatment.
Enlargement of style and its unusual persistence as
a result of application of growth regulators has been
recorded in tomatoes (40) and in oranges (88).

The Leaf
External Modifications.
Under delayed foliation has been mentioned the fact
that in many cases of leaf emergence, the leaves were
twisted (Plate 5).

Here again, as in certain cases of

flower parts mentioned before, the twisting or curving
was a consistently regular pattern, i.e.

-.ending towards

the axis.
This was not characteristic, however, of the leaves
in portions of the tree which were relatively uninjured.
In such cases, the emergence was fairly normal, but often
with a slightly noticeable twist and the leaf'expansion
was also normal.

But consistently the leaf was narrower,

-72the tip acutely pointed, the serrations more numerous
particularly at the tip, much thicker, not as pliable as
the'normal leaf, and with a stronger and thicker petiole,
and with a very prominent and thick midrib and venation.
Most

of these characteristics are evidentfrom Plate 9.
But distributed over the rest of the tree were all

degrees of twisting at emergence, later showing varying
degrees of expansion, all depending on the extent of injury.
One of the most striking features wasthe number

of

modifications of size and shape of leaves that could be
collected at random from the tree, as a whole when the
leaves had reached maturity.

A representative sample is

shown in Plate 7.
But from whatever portion, the leaves might be
gathered, there were certain common features for all the
leaves from the treated trees.

They were a tendency

towards narrowing and elongation of the leaf, the thickness
of the leaf, the prominence of the veins and the midrib,
greater number of serrations, and the apex of. the lea.f
being scute and pointed.
In other respects, there were differences.

Some of

the leaves were chlorotic or had a mottled appearance, and
in some, the veins were translucent and on the whole had
the appearance described by Zimmerman and Hitchcock (109)
as resembling virus infected leaves.

-73But in the case of leaves coming from relatively
uninjured portions, it was usual to find the leaves actually
looking greener than the normal leaves, indicating stim­
ulation to chlorophyll formation.

Such stimulation by

plant growth regulators has been indicated by workers (73,
74).

Internal Structure.
A study of the internal structure of the leaves reveals
a few important features as indicated in the diagrams
(Plate 23).
The cross-section of the midrib shows the increased
size of almost every region in it, particularly the cortex,
the vascular tissues, and the fiber-sheath.

Here again

the fiber-sheath is not continuous, though shown in the
diagram- for convenience but consists of groups of fibercells which are discontinuous.

But just as in the pedicel,

the individual fiber-cells" are larger, the individual
groups are biggery and the gaps between two adjacent groups
smaller as a result of treatment.
Here again must be noted the proportional la.rger
phloem zone as compared to the xylem, as was pointed out
in the pedicel.
The cross-section of a segment of the lamina shows
the following features as a result of treatment:

-

74-

The number of layers of cells that form the thick­
ness of the lamina are more or less the same.

Eut there is

a greater increase in size of the cells, particularly the
length, and there is a marked increase of intercellular
spaces both in the palisade and spongy parenchyma.
In fact, the increased thickness of the treated
leaf is almost solely made up by the. elongation of cells
in cross-section and by the increase of intercellular
spaces.

There has also been increase in the size of the

epidermal cells,
A surface view of the epidermal cells reveals
that the individual stomata are larger in the treated
leaf.

A longitudinal stretching of the epdiermal cells

is 8.1so indicated.

Discussion.
The treatment

in our

increase in growthof the
increase in growth

midrib and veins, and also

of. the

work relating to this

experiments thusresultedin

mesophyll.

Someprevious

is of an interesting nature.

Avery

(2) working with leaves of Nicotiana was the first to
correlate growth of the midrib and probably of the larger
lateral veins with auxin concentration.

He indicated that

auxin is not directly concerned in the growth of the

-75lamina, it giving no response to applied auxin,

'dent

and Thimann (105) and Went (102) also suggested distinc­
tion between the growth of the vein which can be increased
by auxin application and growth of mesophyll which is
independent of auxin.

Bonner (17) went further and ob­

tained gross enlargement in area and thickness of the
leaf sections of tobacco and radish grown in pea diffusete and the internal structure of such treated leaves
showed that there was cell enlargement and marked increase
of intercellular spaces of the spongy parenchyma, a
result that is identical to ours.

He concluded that the

growth of leaves is also controlled by a hormone.

It is

therefore of deep interest to consider here in our exper­
iment that a mixture of 2,4-dichlorophenoxyacetic acid
and naphthaleneacetic acid, in the case of the leaf, have
not only substituted for the 'auxin in increasing the
thickness of the veins and midrib but has also substituted
for or stimulated the production of hormone for the growth
o f .mesophyll.

The Shoot-growth in Spring and Summer
Among the observations made on the spring growth was
the fact that there was. a tendency for reduction in length
of the shoot, varying in degrees.

But invariably, the

stem was much thicker, firmer and. stronger as. a result of

-76treatment.
Plate 17 shows the various regions as seen in crosssection.

There may be noted certain simularity in

features between the cross-sections of the annual growth
and the pedicel.

Even the characteristic shape of the

vascular cylinder is similar.

The points explained in

connection with pedicel with regard to size, shape, and
character of cells in several tissues as well as broad
features of development, are almost generally applicable
to the spring growth, as far as histological observations
are concerned.
It is here, however, that the points regarding the
comparative development of phloem and xylem can be even
more emphatically mentioned.
In the cross-section of the untreated stem, the radial
width of the phloem zone is only one-third to one-half of
the xylem region, whereas in the cross-section of the
treated, the position is almost the reverse; at any rate
the radial width of the phloem region is greater than that
of the xylem.
Besides this, the difference in size of the xylem
vessels between the treated and the untreated is very
remarkable.

The individual vessels of the normal stem

are in many cases more than double that of the treated

-77stem (Plate 17) in spite of the fa.ct that the cross-section
of the treated pedicel itself is so much larger.

This

indicates that not only has there been increased activity
of phloem as a result of treatment but that there has been
relative inactivity or even inhibition of the xylem.
Inhibition of xylem as a result of treatment with growth
regulators has been reported by Swanson (86).

-78-

5. Other Observations
Influence on Period of Maturity of Fruit
No detailed studies of this had been planned.

But

during the last days of ripening of fruit on the tree,it became evident that some of the fruits on treated trees
were catching up with those on the untreated, with regard
to ripening.

Even then, when on the 28th of July, it

was found that most of the sour cherry fruits were ready
to be picked and samples were taken for measurements and
detailed observations, it was not expected that enough
fruits of the same stage could be obtained from the
tree,ted sour cherry for such examinations, because of the
initial delay in opening of flowers,

But on close exam­

ination of the tree, particularly of the higher levels,
it 'showed that many of the fruits had attained that
stage and could be picked on the same date.

Considering

that there was a delay in bloom by about 7 days, this
was a fairly definite proof of earlier maturity as a
result of treatment.
It is of interest to note here that in varietal
differences in period of maturity in sour cherry, Tukey
(95) has reported that the difference in duration is re­
flected only in the duration of the period of delayed
increase (Stage II) and the durations of the other stages
are not affected.

-79In trying to trace indications of the stage in which
the treated.sour cherry made up in the duration, the pre­
served speciinens were ex3,mined step by step, for external
evidences of the sise, color, and firmness of fruit.

Th3

evidences tended more towards accelerated rioening occuring in the last stage.

The indications are that after

the completion of hardening of the stony pericarp in
stage II, the stimulus is transferred from that area to
the tissues of the fleshy pericarp and accelerates there
the chemical and physical processes associated with
ripening.

Further work on the modifying influence of

growth regulators on the normal pattern of development
and maturity of cherry fruits as described by Tukey (95)
would be of utmost interest.
The most remarkable effect on the period of maturity
of fruits upto date is the report of Blondeau and Crane
(15) that the period of maturity of figs was reduced
from ISO da.ys to 60 days by the use of 2,4,5-trichlorophenoxyacetic acid.

Earlier ripening by growth regulators

has been reported also by other workers ('67, 35, 3).
In this connection it may be stated that there are
certain factors that are likely to mislead in the matter
of determining the date of ripening of the treated sour
cherry.

The color of the fruit never.attains the deep

color of. the normal fruit, and this difference is partic-

-80ularly accentuated in the sweet cherry.

Again, the firm­

ness of the pedicel helps in holding; the fruit on the
tree much longer on the treated tree, even though the
fruit has reached its maturity earlier, giving delayed
observations an impression of delayed ripeness.

More­

over, even a month after the normal date of harvest there
would be a few ripe fruits on the tree because of the
unduly delayed opening of many buds.

Influence on the Storage Quality
When the fruits of sour cherry were harvested on
July 28th and the observations and measurements required,
■were made, the rest of the fruits were kept away in the
cold storage room, with the idea that they might later
be required for any further checks, if needed, on some
of those already made.

When 10 days later, these samples

were taken out of the cold storage'roon, the treated fruits
were well on their way to^vards decay, whereas the fruits
of the control tree continued to be firm,

ilo detailed

studies were possible, as at that time not many fruits
were available for comparative study.

Depreciation of

storage quality of fruits of plants or trees treated
with plant growth regulators has been reported by others
(35, 3).

-81Influence on Composition of Fruit
It seemed evident from the taste and flavor of the
treated fruit that some changes in its composition must
have occurred.

The fruits were therefore analysed.

The determinations as shown in the table below (Table 3 )
were made for sour cherry.

They were averaged values of

the results from replicate determinations, expressed on
the weight of the pitted fruit except for the pits
which are expressed on the weight of the whole fruit,

_____________. Table 3.____________ ______ _____
Per Cent_______ _ _
Ml. 0.1 N
Dry Matter "Total Sugar
Pits acid/gram
Control

13.67

7.39

11.63

2.03

Treated

11.15

5.04

20.93

1.85

From this analysis, the following points are clear
1.

The weight of pits has been almost doubled as a

result of treatment.

The increased weight, thickness and

size of the pit have previously been mentioned.
3.

The normal fruit shows increased percentage of

dry matter, total sugar and acidity.

This is the compo­

sition of the pitted fruit and not of the whole fruit.
As such it gives an idea of the composition as it affects
the quality of the edible portion of the fruit.

— 82—

The decreased contents of sugar and acid in the pulp
are reflected in the flavor and taste, the poorer quality
of which has been noted previously under the description
of the treated fruit.
However,'to find out how the dry matter and sugar
are affected, as percentages of the whole fruit including
the pit, since the pit in the'case'of the treated sour
cherry fruit forms a much larger proportion, than the
untreated, this time samples of sweet cherry were tested
on this basis.

The following determinations in Table 4

are the averaged values of the results from replicate
determinations expressed on the weight of the whole fruit.

_____________
T ;cle 4._________________ _________
_____ Per Cent_____ _
Dry Matter
Total Sugar
Ml. of 0.1 I acid/gram
Control.
Treated

24.5
. 25.1

8.85

1.0?

9.25

1.40

In connection with this data, it may be mentioned, that,
the sweet cherry fruits that were used were not as uniform
as in the case of sour cherry, for the obvious reasons
that fruits of very uniform size and stage were not avail­
able .

Even so, as a total content in the fruit including

the pit, the dry matter and sugar have increased, as antici­
pated.

— 83—

Stewart and Klotz (88) reported that in oranges, as
a result of application of 2,4-D sprays, the tota.l acids
and soluble acids were decreased in the fruit juice and
the percentage of rind and sap were increased.

Clark

and Kerns (28) observed that in pineapples, spray-applicationS'of A-naphthaleneacetic acid resulted in decrease
of 2° Brix in the juice.

( M E R A L -DISCUSSION
Translocation of Stimulus
Among the most significant observations in this
study is the remarkable influence of the treatment on
every plant organ and every aspect of annual growth.
This indicates transport of the "spray-stimulus" through­
out the plant as a whole.

Some workers (6, 81) have

observed indications that the absorption of such spray
materials is first through the leaf and petiole into
stem.

That it was clearly so under conditions of our

experiment is indicated by the high physiologies! activ­
ity that was first shown by the leaves and the petioles
where this activity led to a prevention of abscission of
the leaves.
In trying to decide through which of the tissues,,
the stimulus is translocated, Bausor, Reinhart and Tice
(9), by observing distant effects of application of a
grov/th regulator to tomato stem suggested that "the dis­
tant movements were probably confined to the xylem
and especially to the external phloem".

Mitchell and

Brown (62) observed that the movement of 2,4-diclilorophenoxyacetic acid stimulus in plants was associated with
the translocation of organic materials from the leaves
into other parts of the plant and concluded that the

-85-

translocation was '’apparently confined to living tissues,
which indicates that it travels mainly in the phloem and
parenchyma cells”.

We have very definite indications in

our experiments that the phloem in general seems to be
the most important tissue for such translocation.

We

have shown relatively higher activity in phloem in almost
every organ of the plant, the leaf, the stem, the pedicel,
the fruit.

We have particularly shown indications that

the xylem is not activated so highly and in fact
given instances of their

have

inhibition, and as far as the

evidence of these experiments go, the xylem probably does
not play an important role in this respect.

Besides all

this, one fact has particularly struck us, viz., the fact
that curvature towards axis has been shown by the calyx,
the petals, the stamens and leaves —

all organs in which

normally the. phloem is on the side away from the axis,
indicating that curvature has been cansed because, of
elongation of the cells on the side of the phloem.

In

the case of the fruit, mobilisation of food was' greatly
increased, as evidenced by increased dry matter mentioned
under composition and that this mobilisation and translocation of stimulus was

directed to the. nearest tissue

of the phloem, viz., the

stony pericarp, adds up to the

indications of the importance of phloem in translocation
of stimulus.

.

-SSThe Order in Succession of■Responses
An orderly succession of responses is a striking
feature among the observations
Firstly, the action on the petiole and leaf
almost immediately following treatment, causing
inhibition of flower and leaf-buds.
Secondly, a release of the inhibition of flowerbuds, leading to opening of flowers and their
normal subsequent functioning.
Thirdly, a release of the inhibition of leafbuds leading to emergence of the leaves and.
their normal subsequent functioning.
It is obvious that this orderly succession of events
is tied up with the state of growth of the tissues at the
time of application of stimulus, the mobilisation of food
materials to the points of activity at the expense of
other growing portions of the plant and the movement of
that activity from one set of tissues to another, releasing
the inhibitions and activating them, in succession.

To

explain this clearly, there is earliest activity .in the
leaves and petioles, because they are the first points
of absorption, probably because they are relatively the'
most tender at the time of spraying.

How, the high physio­

logical activity caused at these portions of the plant

-87mobilises the necessary food materials from other parts
of the plant, causing inhibition particularly of both the
flower-buds and the leaf-buds.

After having set up the

stimulus there, the stimulus now seems to move to the
next set of tissues which are in a growing condition.
Of the flower-buds and the leaf-buds, according to
Chandler (27), leaf-buds are differentiated much earlier
than the flower-buds, indicating that in the end of Sep­
tember, it would be reasonable to assume that the tissues
are more tender in the flower-buds than in the leaf-buds
so that the stimulus acts more readily .on the flower-buds
than on the leaf-buds.

T^is releases inhibition at those

points and at the same time accelerates their activity
and by the mobilisation process continues to cause inhi­
bition in the remaining growing portions of the plant,
which are particularly the leaf-buds.

This explains the

reason for delay in releasing inhibition of the leaf-buds,
ultimately causing delay in emergence of leaves.

These

conclusions are supported by the findings of workers on
the nature of bud-inhibitions, the mobilisation of food
factors, and the kind of tissues most readily acted upon,
ail as a result of application of growth regulators.
Regarding the mobilisation of food factors at the region
of activity of growth regulators, a consistent point of
view as a result of experimental data have been presented

-88-

by many workers (89, 69, 65, 97, 8, 7, 30, 52).
.Regarding the fact that the readiness with which plant
growth regulators act on a tissue depends on its growing
condition, it-lias been confirmed by many workers' (101,
87, 41, 1).
Regarding the nature of inhibition itself, a large
amount of literature has been accumulated (for example,
90, 92, 104, 103, 53, 68).

Went (104) explained clearly

that ,!the inhibition is due to.removal of growth factors
(in the avena coleoptile, the food factor) from the zone
of inhibition, which are then accumulated near the place
of application of the active substances".

The findings

of Went in another report (103) are of particular interest
to our experiments, where as a result of application of
growth regulators, for two to four or more days,.the buds
were completely inhibited and that the inhibition was ■
then "almost instantaneously and completely released" and
"it even seems that the initial growth of the buds was
slightly more rapid than when they had first been inhib­
ited".

This is in accord with our observations that

in spite of initial inhibition, the growth was highly
accelerated during the subsequent period prior to opening
of the bud.

The Vascular System
The histological studies have revealed that among
the most significant responses of treatment has been
the development of the vascular system,,almost out of
all comparison to the normal.

There was no organ arising

out of the subsequent growth to the treatment that did
not show this response, and we have described its gross
development in the annual

shoot, in the leaf, in the

pedicel, in the different parts of the flower, and finally
in the mature fruit.

In almost all of the literature

concerning histological responses of growth regulators,
activity of the vascular tissues has been recorded but
it seems to the author tha.t only a few have recorded it
with the emphasis that it needs.

For, in going through

details of the responses in literature, one is struck
with the fairly close correlation between the growth reg­
ulators and the vascular system.

Among those that have

laid emphasis on this aspect, Overbreek (78) reported
that "auxin is most effective in inhibiting lateral buds
when introduced into the vascular system of the stele....
This indicates that the place of action from which auxin
controls development of the lateral buds must be the
vascular system".

He stated also that "any treatment

leading to the development of lateral buds is followed

-90-

by an increase in the vascular supply to these buds”.
The whole trend of our observations in this respect seem
to amply bear this out.
But in dealing with the relationship of plant growth
regulators and the vascular system, one of the most strik­
ing effects of these substances that is noticed when
going through literature is the consistent tendency for
vascularization of derived tissues even outside the
normal regions of existence of vascular strands,.for
examples in such unusual places as the pith, the endodermis, etc. (51, 53, 79, 42).

Laibach and Fishnich (54)

noted in coleus that new vascular bundles appeared among
the three ’originally present on each side.
There is no doubt that the vascular system has played
an important role as a conducting tissue in producing all
the responses which we have recorded, such growth responses
as the increased thickness of organs - the stem, the leaf,
the pedicel, the receptacle and almost every other part
of the flower - and ultimately, in the increased weight
of the fruit itself.

There is also no doubt that it has

played its part in all the formative responses that we
have noticed, particularly in the fruit, some aspects of
which we will reserve in dealing with the discussion of
the size and shape of fruit.

It has also played its part

in strengthening plant organs and making abscission

-91phenomena difficult.

Other Histological Responses
In other histological responses, it has been in
consonance with the general feature of behavior of the
growth regulators to the effect as expressed by Kraus,
Brown and Hamner (51) that none of the types of cells
was fundamentally different from cells occurring in the
plant grown under the usual conditions of culture and
environment.
In our experiments, the activity of the growth
regulators has been greatest in the vascular region and
has been mostly confined to enlargement of cells in the
others.

The Size
It has been previously mentioned that the size has
largely been unaffected by treatment.

This leads one to

suspect whether size in the cherry is a genetic factor,
not easily affected by either internal or external environ­
mental changes.

A discussion of this aspect is beyond

the scope of this paper.

But one would have, however,

expected an increase in size as a result of all the
factors for accelerated growth, particularly the increased

—92—

conductive tissues and the increased mobilisation of
food materials.

In many experiments of inducing fruit-

set with plant growth regulators, significant increase in
size has. very often been obtained (113, 108, 99, 73, 40,
74, 72, 88}.

Even in our experiments, the increase in

size of organs such as the stem, the pedicel, and the
stamens has been the rule but the fruit has increased in
weight and has been modified in shape almost out of
recognition, but still the size has not increased.

Eut

to us, the greatest factor that has been responsible for
this end result is the role played by the stony pericarp,
a structure similar to which is not found in most of the
fruits in which increase in size has been reported by
the use of plant growth regulators.

Sinnott (8-3) in

discussing the differences in fruit sizes of the cucurbits
reported evidence that in the case of smaller size, Ha
more important factor in limiting the amount of expansion
is the deposition of the secondary cell-wall, which soon
becomes so strong that further enlargement is impossible.
The fact that it is commonly those types (notably the
small fruited forms) with the least amount of cell-expansion which become the most hard and woody at maturity,
and the ones with relatively great cell expansion which
tend to remain soft (like the pumpkins and watermelons)
seems to indicate the importance of secondary wall forma­

tion in limiting growth*’.

Such a limitation of size has

occurred in the treated cherries on account of the second­
ary wall thickenings of the stony pericarp.

Reference to

the table on page 45 will show that the weight of the
treated stony pericarp has been more than doubled by
treatment.

This gives an indication regarding the extent

of physiological activity that has gone towards the forma­
tion of a highly compact tissue, which has controlled the
ultimate size of the fruit, from expanding.
All this also explains as to why the size of the
pedicel which has increased even as far as nearly three
times the normal, as a result of response, has not pro­
duced an increase in size of fruit, whereas in some
experiments the size of fruit has been to some extent
influenced by the size of the pedicel (84, 28).

The

pedicel, however, through its increased size of conducting
tissue has contributed towards increase of the total
weight of the fruit and has therefore played its expected
role.

Shape or Form
One of the most puzzling questions that are involved
in these experiments is regarding the consistent and
definite change of shape of the fruit as a result of treat-

rnent.

It has long been a fundamental problem to biologist

as to what factors contribute to differences in form.
Talking broadly about form in animals, Huxley (47) spoke
of the growth gradients which were ’’either directly or
indirectly correlated with the morphogenetic gradients
or fields of child, Weiss and others and in general with
the various polarised and field effects in the animal
body”.

He also talked of the two phases of development

which together ultimately decide the form and called them
the "auxano-differentiation" and the "histo-differentiation11.

Coming down, however, to differences in fruit

form within the varieties of the same plant species, Burr
(34) in a study with the cucurbits suggested a significant
relationship between the field forces in the fruit and the
form which it ultimately assumes.

But as Burr and Sinnott

(25) have stated, ’’the morphogenetic implications of the
paroblem of electrical correlates of organic f.orm are not
well understood" and a discussion of this in relation to
the change in shape of the cherry fruit under these exper­
iments is beyond, the scope of this paper, except to state
the application of plant growth regulators might result
in modification of the field forces in the fruit.
But there are a few points which need to be stressed
in this connection.

First of all, it is the elongation

aspect of the fruit.

That the fruits are elongate in

shape, Tukey and Hamner (36) emphasized with regard to
cherry, under almost identical treatment to ours and it
was so in our experiments as previously described.

These

are not the only reports of tendency of fruits to elongate
as a result of treatment with growth regulators.

Stewart

and Klotz (88) reported Washington Havel oranges and
Valencia oranges both of which became cylindrical in
shape as a result of spraying trees with 2,4—D.

Eryant,

Vincent and Schafer (22) reported that as a result of
2,4-D spray to the apple trees, McIntosh apples, normally
round oblate, had become oblong in shape and Jonathan
had changed from round conic to oblong conic.

In some

experiments, where changes in shape have been noticed as
a result of treatment with growth regulators, they have
not been definitely described since they w.ere not presum­
ably important to their main subject of research and nave
therefore been mentioned merely as 11a b n o r m a l , "misshapen”
or "malformed".

But where there was a possibility of

looking at the photographs of such fruits, there seemed to
be no mistaking the tendency for elongation, at least in
most of the fruits photographed (109, 77),

It is not

only the fruits that are elongated; the leaves, and parts
of the flower, like the petal and the stamen, have also
shown this characteristic.

The surface view of the epi­

dermal cells in the. petal (Plate 21} and in the leaf
(Plate 22) show definite longitudinal stretching.
Particularly in the petal, this stretching has resulted
in the leveling up of the wavy outline of the cells.

An

examination of the longitudinal section of the fruit also
shows the elongation of the individual cells parallel to
the axis.

All this means that the basic pattern that re­

sults in an elongation of the fruit is nothing else than
that characteristic of auxins —

cell elongation.

This

seems to explain the first main characteristic of the
fruit around which the principle modification of form
has been built up.
The next thing that needs explaining is the modifi­
cation of the shape of the fruit as a whole from a
roundish shape to oblong conic.

As previously explained

under comparative description of treated fruits, commencin
with a maximum diameter near the stem end, there is a
tapering down to a point at the apex.

In this respect,

there seems to be more or less a definite correlation
between the shape of the fruit and an approximate outline
of the stone.

If we go back to the differentiation of

the zone destined to become the stony pericarp, Tukey
and Young (96) have mentioned that it had happened when
the ovary was examined 18 days prior to full bloom.
same thing applies to the pattern of vascular system.

The

— 97—
When the cherry ovary was examined by us, at the time of
opening of the flower, this vascular system was closely
woven around the stony pericarp zone.

We have also

explained that this was so throughout the life, of the
fruit.

We have also indicated that the nearness of the

stony pericarp area to the vascular system seems to have
been responsible for a greater stimulus to the growth
of this particular tissue and the proliferation of the
vascular tissues themselves has resulted in an undue
concentration of the vascular system in one place, with
little of that ramification, which is characteristic of
a normal fruit, as per Tukey and Young (96).

The vas­

cular system after all is akin to a skeleton to which
flesh of the fruit is the "clothing" and what form or
appearance would be finally taken by the fruit also de­
pends to some extent on the vascular skeleton.

Here in

the case of the cherry fruit, the vascular skeleton hap­
pens to follow' the outline of the s'tony pericarp and
that outline is more or less followed by the final shape
of the fruit.

Further, the points of reach of nutrition

or even of the stimulus from a plant, growth regulator
depend on the distance from the vascular strands and
these strands in our experiment are close to the stony
pericarp and it seems as though the resulting outline of
the fruit envelops points approximately equidistant from

the vascular tissues and hence of the stony pericarp.
Lastly, the fairly thick short portion of the style
that persists with the mature fruit adds up to the final
characteristic shape of the fruit of the treated cherry.

The Prepond.erent Effect of 3.4-dichlorophenoxyacetic Acid.
Mixtures of .growth, substances have been now and then
used with the hope of increased effectiveness (85, 44, 2S,
4).

In some instances competitive action has been noticed

as in the combination of phenylbutyric acid and indoleacetic a.cid reported by Skoog, Schneider and Peter (85).
There are specific instances, however, when 2,4-dichlorophenoxyacetic acid and naphthaleneacetic acid have been
combined os a stop-drop material for apples but no more
effectiveness was found than their individual action (44,
29, 4).

Nevertheless, the relatively shorter period of

effect of naphthaleneacetic acid has been definitely ob­
served by several workers (44, 53, 93).

Thompson and

Eatjer (93) have emphasized also on the greater intensity
of effect of 2,4-dichlorophenoxyacetic acid.

Besides this,

Hitchcock and Zimmerman (47) while- obtaining delayed bloom
in spring in cherries as s. result of summer application
of potassium naphthaleneacetate, reported development of
only normal fruit at a. normal rate.

In fact, almost all

workers in this field are agreed that naphthaleneacetic

-99-

acid has no formative effects, whereas the formative effects
of 2,4-dichlorophenoxyacetic acid have been well-known (32,
41, 39).
With this background, if we compare the duration of
effect of treatment in this experiment lasting for ten
months, its intensity in growth responses and the strong’
formative effects, there seems to be no doubt that 2,4-dichlorophenoxyacetic acid has shown a preponderant effect
over naphthaleneacetic acid at the proportion of concentratione used.

It also lea.ds to the supposition that the

use of 2 ,4-dichlorophenoxyacetic acid by itself, at ade­
quate concentrations, is likely to lead to the same type
of responses, as observed in this experiment.

Practical Applications
Importance to the Fruit Grower
From the point of view of a fruit grower who is con­
cerned with fruit as the economic product, and with con­
tinued maintenance of the health of the tree, the chem­
icals used, at the proportions and concentrations mentioned,
have not in our experiments led us to encourage their
use, considering the extent of injury to the tree, reduc­
tion of yield, and lowering of the marketable quality of
the fruit.

But the fact that there were certain portions

of the tree which were relatively healthy, indicates that

-100-

injury to the tree and consequent reduction in yield nay
perhaps be lessened by lowering the concentrations.

Such-

lower concentrations, if effective may also lessen the
extent of harmful effects on quality.

It is even con­

ceivable that by further trials with several 'concentra­
tions, it is possible to arrive at an-optimum in which
the stony pericarp is not unduly stimulated but the stim­
ulus will be directed towards increasing the sugar content
and dry matter of the pulp.

After all, the final result

as we have noticed has been to increase the sugar content
and dry matter of the fruit as a whole.
As mentioned by Hitchcock and Zimmerman (46), the
definite effects of delay.in opening of flower and leaf
buds through the use of plant growth regulators can be
utilised in a variety of ways, in protecting the fruit
trees from spring frost injury, regulating the growth and
development of plants in the nursery, and extending the
total period of flowering in some ornamental plants.

Importance to the Taxonomist or Systematic Pomologist
To the taxonomist and the systematic pomologist the '
findings present a problem, because of the ever-increasing
use of plant growth regulators, particularly of 2,4-dichloro­
phenoxyacetic acid, for various purposes.

For instance,

there have been reports of the formative effects on apole

.

-

101

-

fruits in orchards, where 2,4-D has been used as herbi­
cide (32, 56).

The modifications as we have seen in the

cherry are thorough with regard to shape, thickness of
skin, color of skin, flesh and juice, taste, flavor and,
in fact, in almost all characters on which a systematic
pomologist bases his classification of varieties.
Often stone markings and patterns in a drupe such as
the cherry have been described as valuable evidence for
identification of a variety, as for example by Blake and
Edgerton (14-).

On© of the responses of treatment in

our experiment has been the entire alteration of the
surface character of the stone.
Under such modifications as we have reported in the
experiment, of also the leaf, floral and growth characters,
the taxonomist does not have even the hope of identifica­
tion of a variety by tree characters, the identification
of fruit having failed.

Such findings, however, open up

to the taxonomist the vista of possibilities of growth
regulators in this direction and impress on him the fact
that' plant descriptions do not stay static but that they
need 'modification with the progress of such application
of science.

Importance to the Horticulturist
In connection with the diagnostic problems that a

-

102-

horticulturist meets with tree behavior, it is interesting
to note that Kinman in 1930 (49), in studying the problem
of unproductive cherry trees in California, reported
certain characteristic symptoms in the way of morphological
modifications observed as a result of treatment in our
experiment.

According to him "the shape and color of

leaves on the unproductive trees differ from those of
productive trees, the blossoms are defective, and many
blossom buds fail to open.
are very irregular."
chlorophyll.

In affected leaves the margins

There was also mottling due to less

There were changes in shape of the fruit.

A glance at the photographs of leaf modifications showed
them to be similar in many respects to those in our ex­
periments.

The author'at that time, IS years ago, consid­

ered such trees a result of propagation of sporting
branches.

But a similarity of modifications to those

described by us leads one to suspect the probabilities
of hormonal maladjustments within a tree and of the role
that the knowledge of such responses as we have described
might play in the field of diagnosis.

Importance to the Geneticist
To the geneticist, who considers such characters as
the shape and sise of the leaf, the shape of the floral

parts, the si?e and shape of the fruit as functions of the
gene, it gives an idea of the hormonal complexities that
might be allied with the genetic complex, in the repro­
duction and maintenance of. characters.

-104SUMMARY
1.

Gherry trees (Prunus avium and Prunus cerasus)

v/ere sprayed in the fall (September 23, 1947) with a
mixture of 100 p.p.m. of 2,4-dichlorophenoxyacetic acid
and 30 p.p.m. of naphthaleneacetic acid and the subsequent
morphological and histological responses studies the next
growing season.
2.

There was injury to both the vegetative and floral

buds, spurs and twigs, resulting in reduction of leaf
area and fruit-set.

Light, vigor and the method of

spraying itself influenced the degree of injury in the
various parts of the tree.

The sweet cherry showed more

injury than the sour cherry.
3.

There was delay or even complete prevention of

abscission of all plant parts that normally absciss, be­
ginning with the leaf-fall to the dropping of mature
fruits.

Evidences were cited for questioning the contention

that the effectiveness of a plant growth regulator de­
pended on the anatomical type of abscission.
4.

The opening of floral and vegetative buds was

delayed and very irregularly distributed.

In no cs.se was

the delay solely due to injury, where injury was severe
but was to some extent direct result of treatment, as
subsequent formative patterns revealed.

-105-

5.

The modifications in the fruit as a result of

treatment were so thorough that the fruit was not recog­
nizable as belonging to the specific variety.

The shape

became elongate and pointed, broader at stem end and
tapering to a point at the apex, instead of the roundish
shape of the normal fruit.

The skin was lighter in

color and thicker; the flesh and juice also lighter
colored, with poorer taste and flavor.
heavier by as much as 18 per cent.
development of the stone.

The fruit was

There was an abnormal

It showed a close correlation

to the fruit in shape, had a rough, variously ridged
surface compared, to a relatively smooth surface of the
normal stone: its size increased by as much as 34.0 per
cent, .and the weight by 135.0 per cent and the thickness
of the stony pericarp by 109.0 per cent.
The pedicel increased in thickness by nearly twice
that of the normal, as also the receptacle.

The pedicel

was also much firmer to the touch and adhered strongly to
the tree and to the fruit, enhancing the hanging.quality
.of the fruit.
Against all the rest of the modifications, there was
one aspect of the normal fruit that did not change —

the

si ze.
■ S.

A study of the histological development of the

-106fruit revealed distinct effects of the treatment.

The

vascular system proliferated abnormally and shifted its
position from the center of the fleshy pericarp and
adhered and almost d i n g e d to the outer layer of the
stony pericarp, forming a massy network, and ramifying
very little. . The tissues of the stony pericarp also
showed undue activity and proliferation.
In the other tissues of the pericarp, while the
pattern of shape of cells broadly resembled the normal,
the cells of the hypodermal layer showed increased en­
largement and relatively higher degree of tangential
elongation, compared to the normal.
7.

Histological study of the pedicel, the petiole

and midrib of leaves, and the annual growth showed an ,
increase in size of almost every tissue inside due to
enlargement of cells, and increased activity of the vas­
cular system, but of more of the phloem, than of the
xylem.

There were, in fact, evidences of inhibition of the

activity of xylem.
The pericycle fiber cells became larger, both individ­
ually and as groups, and formed a more continuous sheath
around the vascular cylinder, contributing to the strength
of the pedicel, stem, and petiole and midrib of the leaf.
8.

The accessory parts of the flower were also

-107affected.

The calyx lobes, the petals, and stamens all

had a definite tendency to bend towards the axis.

Eoth

the calyx lobes and the petals were narrower, longer,
and thicker and with a much .stronger development of the
vascular system than the normal.

The filaments of the

stamens were thicker and longer and the anthers larger
and more pointed at the end.

The style was thicker and

a portion of it persisted with the mature fruit.
9.

.

The leaf showed bending at emergence, in the

same direction as parts of the flower mentioned above.
The expanded leaves were generally narrower, longer,
thicker, with acutely pointed tip, deeper and more numer­
ous serrations, with a very strong and thick petiole and
very prominent midrib and venation.

There were, however,

several modifications in size and shape, though a
higher ‘
length/breadth ratio compared to the normal was
always consistent.
The internal structure of leaves showed enlargement
of cells and marked increase of intercellular spaces.
The treatment was shown to substitute for the auxin in
increasing thickness of veins and midrib and for the
hormone for growth of mesophyll, both specifically differ­
ent according to published literature.
10.

There were indications of earlier ripening of

-108the fruits due to treatment and of the transfer of stim­
ulus after the completion of hardening of the stony peri­
carp to accelerate the activities of the fleshy pericarp
towards ripening.
11.

There were indications of depreciation of

storage quality of mature fruits, due to treatment.
12.

Chemical analysis of the fruit showed increase

of total sugars and dry matter in the fruit as a whole,
a large part of which contributed to the abnormal
development of'the stone, resulting in lower proportion
in the pulp, and thus contributing to the poorer marketing
quality.
13.

The translocation of stimulus was discussed and

the evidences for the phloem playing the most important
role- in this furnished.
14.

The orderly succession of responses from the time

of application of treatment was analysed and correlated
with the gradation of growth of the tissues or organs.
15.

The general influence of growth, regulator

treatments in inducing greater vascular development was
brought out.
IS.

The role played by the abnormal development

of the stony pericarp in controlling size and by the
vascular pattern and cell-elongation effect of growth

-109regulators in addition, in evolving shape was brought out.
17.

The preponderent effect of 3,4-dichlorophenoxy-

acetic acid in the mixture applied ?;as explained.
18.

The practical applications of the results

are listed.

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69. _______________ , and Stuart, N. W. Growth and metab­
olism of bean cuttings subsequent to rooting with
indoleacetic acid. Bot. Gaz. 100:627-650. 1939.
70.Moon, H. H . , Regeimbal, L. 0., and Harley, 0. P.
Some residual effects of sprays containing 2,4-D
on apple trees. Proc. Amer. Soc. Hort. Sci. 51:
81-84. 1948.
71* Hullison, Tv'. R. Histological responses of bean plants
to tetrahydrofurfuryl butyrate. Bot. Gaz. 102:
373-381. 1940.
72. Murneek, A. E. Results of further investigations on
the use of "Hormone" sprays in tomato culture,
Proc. Amer. Soc. Hort. Sci. 50:254-262. 1947.
73.

■ ___
. Wittwer, S. H., and Hemphill,
D. D.
"Hormone" sprays for snap beans. Proc. Amer. Soc.
Hort. Sci. 44:428-432. 1944.

74.

_______________
.
Supplementary ''Hormone11 sprays for greenhouse grown
tomatoes. Proc. Amer. Soc. Hort. Sci. 45:371-381.
1944.

75. Murray, M. A., and Whiting, A. G. A comparison of
histological responses of bean plants to tryptophane
and to low concentrations of indoleacetic acid, Bot.
Gaz. 108:74-100. 1946.
76. ________
•
________
. A comparison of
the effectiveness of 2 ,4-dichlorophenoxyacetic acid
and four of its salts in inducing histological re­
sponses in bean plants. Bot. Gaz. 109:13-39. 1947.
77. Nixon, R. W . , and Gardner, F. E. Effect of certain
growth substances on inflorescences of dates. Bot.
Gas. 100:867-871. 1939.

-11778. Qverbreek, J. (Van). Auxin distribution in seedlings
and its bearing on the problem of bud inhibition.
Bot. Gaz. 100:133-168. 1938.
79. Palser, B. F. Histological responses of Vicia faba
to indoleacetic acid. Bot. Gaz. 104:243-363. 1942.
80. Pfeiffer, N. E. Anatomical studies of root-production
on application of indolebutyric acid to Giesus
aerial roots. Gontrib. Boyce Thorneson Inst. 8:
493-506. 1937.
81. Pridham, A. M. S. Delayed action of 3,4-D on trees,
sbrubs, and perennials. Proc. Amer. Soc. Hort.
Sci. 50:395-397. 1947.
82. Sass, J. E. Elements of botanical microtechnique.
McGraw Hill Book Company, Inc., Hew York and London.
1940.
83. Sinnott, E. VI. A developmental analysis of the relation between cell size and fruit size in cucur­
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84.

•

'i1 -

11
-v'*'

. Relative growth of pedicel and fruit
in cucurbits. Amer. Jour. Bot. 33 (Supplement):p.10a. 1946.
.

85. Skoog, F., Schneider, 0. L. , and Maian, P. Inter­
actions of auxins in growth and in inhibition.
Amer. Jour. Bot. 29:568-576. 1942,

111-1

86. Swanson, 0. P. Histological response of red kidney
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acid. Bot. Gaz. 107:522-531. 1946.

ll-ll
$&£■

^ „

I ' - l f l

87.

Stewart, W. S., and Ebeling, W. Preliminary results
of 2,4-D as a spray oil amendment. Bot. Gaz. 108:
286-294. 1947.

-llll

111!

88.___________ and Klotz, L, J. Some effects of
2,4-dichlorophenoxyacetic acid on fruit-drop and
morphology of oranges. Bot. Gaz. 109:150-162.- 1947.

1111

89.

llll

Stuart, N. W. Nitrogen and carbohydrate metabolism
of kidney bean cuttings as affected by treatment
with indoleacetic acid. Bot. Gaz. 100:298-311. 1938.

-11.1

'"'111
ill-S
1 -'I--;;'!!'

;;

-118-

90. Thimann, £, V. On the nature of inhibition caused
by auxin. Amer. Jour. Bot. 24:407-413. 1937.
91.
growth.
93.

. Auxins and inhibition of plant
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, and Lane, R. H. After-effects of the
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535-543. 1938.

93. Thompson, A. H., and Batjer, L. P. Factors relating
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. Growth of the embryo, seed and pericarp
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., and Hamner, 0. L. Form and composition
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97.

______ ____ ____________ , and Imhof e , B. Hist- ' *
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98.________ •
_____ , and Young, 0. Histological study of
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-119-

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Some exoeriments on bud-growth.
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The

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1942.
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-131PLATES

Explanation of abbreviations:
OA
00
CU
EP
FP
FS ■
EY
ISP
OSP
PH
PI
PP
SP
SPP
ST
X
XP
CL
/T

—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—

cambium
cortex
cuticle
epidermis
fleshy pericarp
fiber-sheath
hypodermal layer
inner stony pericarp
outer stony pericarp
phloem
pith
palisade parenchyma
stony pericarp
spongy parenchyma
stoma
xylem
xvlem parenchyma
C o lle 'n ch y m a
\/£ISCh /<*V

tlS9««5-

Plate
Untreated sour cherry tree.
Photo .-raphed July 16, 1948

PLATE 1

~

» “V

>.

v

s

1

'^j8y"V-

Plate 2
Treated sour cherry tree
Relative bareness of limbs due to
killing of leaf-buds, by treatment
Photographed July 16, 1948

PLATE

Plate 2

fj?

vti^, ^

Plate 3
Untreated sweet cherry tree
Photographed. July 16, 1948

PLATE

. Plate 4
Treated sweet cherry tree
Framework almost bare due to
severe killing of leaf-buds
Photographed July IS, 1948

PLATE

k

Plate 5

Left - normal emergence from untreated tr
Center and. right - bending and twisting o
leaves at emergence
Photographed May 4, 1948

CD

Leaves of sweet cherry after emergence

Plate

Plate 6
Sour cherry twig from treated tree
with aborted flowers not abscissing,
and narrow, elongate, mottled leaves
Photographed July IS, 1948

PLATE 6

Plate 7
Modification of size and shape of
leaves due to treatment
Top — sweet cherry
Bottom - b our clierry
Photographed July IS, 1948

Plate 1

/

j

Plate 8

Flower buds of sour cherry on
April 24, 1948
Left - tvro twigs - treated - flower
buds retarded in opeining.
Leaves of fall not abecissed.
Right - two twigs - untreated

PLATE

Plate S

Leaves and open flowers of sour cherry

Fros left to right:1. Leaf from treated tree
2. Flower and single petal from treated tree
(The incurving of the petals is shown)
3. Flower with petals removed to show the
incurving of calyx lobes and stamens f rorri .treated tree
. Flower and single petal from untreated tree
. Flower with petals removed to shot'/ the
normal position of calyx lobes and the
normal posture of the stamens
6. Leaf from untreated tree

Plate 10

Sweet cherry flowers
Top.

Left - single petal from treated, tree
Right - single petal from untreated tree

Bottom from left to right1. Open flower from treated tree with in­
curving of petals clearly shown
2. Flower with petals removed with incurving
of stamens, greater thickness of filaments,
larger sized anthers, pointed at apex, and
thicker pedicel, shown
3. Open flower from untreated tree
4. Flower with petals removed

PLATE

Plate 11

Mature fruits of sour cherry
Top - untreated.
Bottom - treated

PLATE 1\

r

Plate 12
Mature fruits of sweet cherry
Top - untreated
Botton - treated

Pl a t e

r

h

M

1

Plate 13

Stones of mature cherry fruits
Top - treated
left - sweet cherry
right - sour cherry
Bottom - untreated
left - sweet cherry
right - sour cherry

Pl a t e

13

Plate 14

Projectoscope drawings
Fig. 1 - cross-section of sour cherry fruit in
early part of Stage II showing tissues
of pericarp (tissues in the locule not
shown)
A - treated
E - untreated
Fig. 2 - portion of a section through fleshy
pericarp of nature fruit showing the
nature and position of vascular
system
A - treated
B - untreated

Z*>fJ

0

a

f i

r'ou

0

t

• -*7/ 3J.V7r/_

Camera lucida drawings
Cellular details of cross-sections of tissues
of the pericarp of sour cherry at commencement
of Stage II (mid-stage of ripening)

§|
f|
H

Left - treated
Right - untreated

H
**

PLATE 15

DC

EP

OSP

51 JlVld

Plate 16

Camera lucida drawings
o
Cellular details of cross-section of tissues
of fleshy pericarp of mature sour cherry fruit
Fig.
Fig.

12abcd-

untreated
treated
epidermis and hypodermis
cells next to hypodermal layer
cells in the middle of the fleshy pericarp
cells in inner region of fleshypericarp

P L A T E lb

a

n

FlGil

Plate 17
Camera lucida drawings
Cross-section of xylem vessels in stem
A - untreated
B - treated

Projectoscope drawings
Cross-section of stem snowing tissue regions
G - untreated
D - treated
Cross-section of p?dicel showing tissue regions
E - untreated
F - treated

Plate n

Co

Plate 18

C ame ra lucida dr awi ngs
Cross-section of comparable portions of the
vascular system in pedicel of sour cherry
open flowers
Left - treated
Right - -untreated

PLATE 18

CA

PH
-CA

Plate 19
Camera lucida, drawings
Gras £*— sections of fiber cells of the pedicels
of ms. -fcure f ruits
—
B —
a

treated
untreated

Cross — sections of comparable portions of
v a s c u l a r system, in sour cherry pedicels
B1 d a y s after the flower opened
C —
C —

untreated
treated

p lk t e

is

Plate 20

Camera lucida. drawings
Cellular details of the cross-sections of
tissues of pedicel ox sour cherry open, flowers
Top - treated
Bottom - untreated

PLATE 20

Plats

21

Pro ject o s c o p e drawings
Fig.

1.

Outline of vascular system in tire
sour c h e r r y petals
Left — u n t r e a t e d
Right — t r e a t e d

Camera l u c i d a

drawings

Surface v i e w
of oetals

of the epidermal c e l l s

Left — u n t r e a t e d
Ri i-'ht — t r e a t e d

P l a t e zi

FI ate

Camera lucida drawings
Surface view of the epidermal cells of sour
cherry leaves
A - treated
B - unt restted
Segments of cross-sections of the sour cherry
leaves
C - treated
D - untreated
Projectoscope drawings
Cross-section of the mid-rib of the sour
cherry leaves
E - treated
F - untreated

PLATE 2*2.

ST

CL

I ST
I
I

EP-

co

: £P

F