SOME MODIFICATIONS IN THE BEHAVIOR OF
LYCOPERSICUM ‘ESCULENTUM: AS A RESULT
OF FOLIAR SPRAYS OF MALEIC HYDRAZIDE

 

Th”?! for flu Dean. of Ph. D.
MICMIGAN S‘I‘ATE UNIVERSITY

KaIapafi-i M. Srinivasan
1960

THESIS

This is to certify that the

thesis entitled
"Some Modifications In The Behavior 0f
LyCOpersicum esoglenigg As a Result Of
Foliar Sprays 0f Maleic Hydrazide"

presented by

Kalapatti.M.Srinivasan

has been accepted towards fulfillment
of the requirements for

Ph 0 D 0 degree in HORT ICIIIJTURE

(7124/2; / xZ/K W’Zéi

Major professor

Date Z05” // [75”
</ (/

0-169

 

LIBRARY

Michigan State
University

 

SOME MODIFICATIONS IN THE BEHAVIOR OF
LYCOPERSICUM ESCULENTUM, AS A RESULT

OF FOLIAR SPRAYS OF MALEIC HYDRAZIDE

By
KALAPATTI M. SRINIVASAN

AN ABSTRACT
Submitted to the School for Advanced Graduate Studies of
Michigan State University of Agriculture and
Applied Science in partial fulfillment of

the requirements for the degree of

DOCTOR OF PHILOSOPHY

Department of Horticulture

Year 1960

/ / /
“r ” V95. 5 [(1/1 {7 ,. Z / [9/4/2114le

 

KALAPATTI M. SRINIVASAN ABSTRACT

Greenhouse experiments were conducted from the fall
of 1958 to the spring of 1960, to study some of the physio-
logical responses of tomato following foliar applications
of maleic hydrazide (MH). Fruit-set in tomato under high
night temperature (700 - 80°F), as influenced by such
applicatons was of particular interest. Other responses
studied were; general growth responses, accumulation of
certain nutrient elements and respiration of roots in MR
treated plants.

The following were the noteworthy results recorded:

1. Tomatoes(John Baer) when grown under high
night temperatures, produced few flowers,
and high flower abscission. Fruit-set was

either poor or absent.

2. Under the aforesaid condition, foliar ap-
plications of NH (20 p.p.m.) made at a time
the first flowers started to open and follow-
ed by growth regulator treatments to fully
Opened flowers ( naphthoxyacetic acid at
50 p.p.m. as an aqueous spray) resulted in

increasing fruit-set significantly.

3. The indications of the experiments were that

difficulty in pollination exists under high

night temperature as a secondary factor,

and that MH applications can counteract the

KALAPATTI M. SRINIVASAN ABSTRACT-2

detrimental effects of high night temperature.

Foliar sprays of MH at 1000 p.p.m. to young
tomato seedlings resulted in the inhibition
of their vegetative and reproductive growth.
The most notable effects were; retardation
of stem and root elongation, increase in
stem diameter, reduction in number of leaves
per plant and decreased length of leaves.

Alteration in appearance, color, texture and

venation of leaves were also noted.

Analysis of MH treated plants (by spectro-
scopic and chemical methods) indicated that
treated plants tend to accumulate lesser
amounts of some important nutrients such as
nitrogen, potassium, phosphorus, calcium, -
magnesium, boron, manganese and copper as
compared to non-treated plants grown under

similar environment and nutritional level.

The rate and total accumulation of phosphorus
were retarded, when tomatoes were grown in
a nutrient culture with varying levels of
phosphorus and treated with foliar sprays of
MH (1000 p.p.m.). The inhibition induced by

MH could not be overcome by increasing the

KALAPATTI M.

SRINIVASAN ABSTRACT-3

level of phosphorus in the nutrient culture.

Foliar applications of MH (1000 p.p.m.) to
young tomato seedlings influenced root
elongation, number and location of root hairs
and respiration of roots. Root hairs were
few and appeared at the very tip of the root.
Respiration and root elongation were inhibit-
ed.

It is believed that MH alters the physiology
of young tomato plants and induce inhibition
of growth by affecting the root-tips, root

"hairs, root elongation and respiration of

roots.

SOME MODIFICATIONS IN THE BEHAVIOR OF
LYCOPERSICUM ESCULENTUM, AS A RESULT
OF FOLIAR SPRAYS OF MALEIC HYDRAZIDE

By
KALAPATTI M. SRINIVASAN

A THESIS
Submitted to the School for Advanced Graduate Studies of

Michigan State University of Agriculture and
Applied Science in partial fulfillment of

the requirements for the degree of

DOCTOR OF PHILOSOPHY

Department of Horticulture

1960

ACKNOWLEDGEMENT

The author wishes to express his grateful thanks to
Dr. C. L. Hamner for the help and encouragement given
through out this work. Thanks are also due to Drs. H. B.
Tukey, H. M. Sell, H. C. Beeskow, and Leo Mericle for
kindly going through the thesis and offering helpful
suggestions. Special thanks are due to Dr. K. N. Satyapal
for the assistance given in the nutrient culture experiments.

The author also wishes to acknowledge some green-

house facilities provided by the Soil Science Department.

TABLE OF CONTENTS
Content Page
INTRODUCTIONOOOO0.0.0....OOOOOOOOOOOOOOO0.000.000.0000. 1
.REVIEW OFLITERATUREOOOOOO00.00.060.000.000000000000000 3
MATERIALS ANDMETHODSOO0.0......OOOOOOOIOOOOOOOOOOOOOO. 14
RESULTSOOOOOOOOOOOOOOO000.......0...OOOOOOIOOOOOOOOOOOO 26
I. Fruit-set in tomato (John Baer) grown under

high night temperature as influenced by

foliar applications of maleic hydrazide,

growth regulator treatment to fully opened

flowers and their combinations................

II. Physiological responses of tomato as influenced
by foliar sprays of maleic hydrazide..........

DISCUSSION............................................. 45
SUMMARY................................................ 52
LITERATURE CITED....................................... 55
APPENDIX............................................... 61

INTRODUCTION

Maleic hydrazide is one of the many chemicals whose
presence in the plant alters its physiological processes.
Applications of maleic hydrazide as a foliar spray to
plants are known to result in the retardation of vegeta-
tive growth, reduced respiration and accumulation of car-
bohydrates (21, 44, 45, 46, 53).

When tomatoes are grown under temperatures higher
than optimal for their development, vegetative growth be-
comes dominant, fewer flowers are produced and is followed
by heavy abscission of flowers. All these factors result
ultimately in poor fruit-set. The entire changes in the
growth and development under high night temperature includ-
ing the poor fruit-set can be explained on the basis of
availability of carbohydrates and its subsequent utiliza-
tion (58, 59, 60, 61, 62). Any attempt to reduce vegeta-
tive growth and respiration would seem to favor accumula-
tion of carbohydrates and improve fruit-set under this con-
diticn. Hence, in an attempt to improve fruit-set in to-
mato under high night temperature, foliar applications of
maleic hydrazide were undertaken.

In addition to the use of maleic hgdrazide for in-
proving fruit-set in tomato under high night temperature,
physiological responses of tomato (i.e. growth responses,

- 1 -

accumulation of nutrient elements, respiration) as altered
by foliar applications of maleic hydrazide were studied.
The objectives of these studies were an attempt to
understand some of the physiological responses of the
tomato to applications of maleic hydrazide and to gain
further knowledge about the manner in which maleic hydra-

zide could induce inhibition of plant growth.

REVIEW OF LITERATURE

Effect of High Night Temperature on Fruit-Set in Tomato:

Tomato sets fruit abundantly when night temperatures
("nyctotemperatures") are between 15° and 20°C and day tem-
peratures ("phototemperatures") are about 25°C. With
'higher or lower temperatures, fruiting is significantly re-
duced or absent (58, 59).

According to Went (62), the factors associated with
fruit-set under higher and lower temperatures than optimal
are different. Under low night temperature the principle
limiting factor appears to be auxin. While under high night
temperature the carbohydrate availability seems to be the
limiting factor (59. 62). Went (61, 62), has shown in his
studies that under high night temperatures the trans-
location of sugars is poor and there is a predominance of
vegetative growth to the detriment of the fruit-set. The
poor fruit-set as well as the predominance of vegetative
growth under high night temperatures can be easily under-
stood on the basis of competition for available carbo-
hydrates. That deficiency of carbohydrates will result in
poor fruit-set in tomato has also been suggested by Kraus
and Kraybill (33) and Howlett (29, 30). Murneek (42) has

indicated that in tomato under conditions that are not

optimal for fruit-set, there exists a negative correlation

- 3 -

- 4 -

between vegetative growth and fruiting.

Poor fruit-set can also result from excessive ab-
scission of flowers. Went (62), observed in tomato under
both high and low night temperatures abscission of flowers
was high. He indicated that abscission of flowers is due
to entirely different factors under high and low night tem-
peratures. Flower abscission under high night-temperature
mainly arises from limitation of carbohydrates while lim-
itation of auxin induces flower abscission under low night
temperature (47, 62). Howlett (29), has shown that de-
ficiency of carbohydrates can induce sterility of pollen
in tomatoes. Hence, under high night temperatures where
-there is deficiency of carbohydrates, failure of pollina-
tion could also be expected.

Once the fruit has set, its subsequent development
is not hampered under high night temperatures (62). On
the whole the poor fruit-set in tomato under high night
temperature seems to mainly rest in the failure of flowers
to develop into fruits. This in turn appears to rest pri-
marily on the availability of carbohydrates. The unfavor-
able utilization of carbohydrates in the vegetative growth
in preference to fruit-set, the production of fewer flowers
tendency for a high flower abscission and the possibility
of failure of pollination should all be recognized in con-
sidering the fruit-set in tomato under high night tem-

perature.

General Characteristics and Present Uses of Maleic

Hydrazide (MK):

The general biolOgical effect is that application of
maleic hydrazide results in plant growth inhibition. Its
chemical ingredient is 1, 2-dihydro-3, 6-pyridazinedione.
The formulations available for experimental and general
uses are:

a. MH-40, a water soluble powder of the
sodium salt of MH, with wetting agent and
sticker, containing 40% MH acid equiva-
lent.

b. MH-BO, a solution of MH, as a diethano-
lamine salt, containing 30% MH acid equi-
valent by weight.

MH is used as a herbicide (14), since its applica-
tions have been noted to be effective in preventing re-
growth of rhizomes (5), flower formation and seed germina-
tion (7, 67). MH treated plants show inhibition of growth
(12, 40, 53), and this property has been made use of in re-
ducing the frequency of mowing lawns, preventing terminal
growth of shade and fruit trees, and for stopping regrowth
of tobacco suckers (51, 67). MH applications can also be
used to substitute hand pruning and for breaking apical
dominance in strawberries and Chrysanthemums respectively
(2, 28). Since MH treated plants show reduced rates of
respiration, it has found applications in preventing storage
losses in onions and sugar beets and extending life of cut

roses (57, 64, 66). Application of MH to plants results in

-6-

the accumulation of carbohydrates, retardation of vegeta-
tive growth, and has also been used for providing winter

hardiness in citrus seedlings (68). MH is used for pro-

motion of abscission of olives (25) and for inducing male
sterility in cucurbits (27).

MH applications are noted to induce an inhibiting
effect on cell division even in dilute concentrations (23).
The inhibibition of cell division in NH treated plants has
been found to be largely restricted to the meristematic
zones (10). Chromosome breakages following applications
of MH are of common occurrence (8). Since the meristems
are influenced,it is not surprising to find as a result of
treatment with.MH, the appearance, growth and development
of plants are altered. MH applications also profoundly
influence the physiological processes such as respiration,

photosynthesis and transpiration (6, 45, 67).

General Growth Responses of Plants, Following Foliar
(Applications of MH:

.Schoene and Hoffman (53) were the first to describe
the effects of applications of MH on plant growth. Since
their report, this compound has aroused interest in ag-
ricultural research. One of the widely reported effects
of application of MH on plants is that it retards their
growth. Naylor and Davis (44), found that a wide group of
plant species show a remarkably uniform effect to applica-
tions of MH. By applying MH as a foliar spray from 0.05

to 0.4 percent concentrations, on oat, wheat, redtop grass,

- 7 -

corn, peas, peanuts, sunflower, cocklebur, tomato, to-
bacco and cotton, they concluded that the following were
the chief responses observed:
1. Cessation of activity of terminal meristem
2. Cessation of elongation of internodal region

3. Increase in stem diameter

Greulah (18), reported much more marked inhibition of
MH treated tomato plants than that observed by Schoene and
Hoffman (53). He found that stem diameter of treated
plants was inhibited rather than increased. In addition
to some of the responses observed by Schoene and Hoffman
(53), Greulah (l8, 19, 20) noted alteration of leaf mor-
phologm,inhibition of leaf growth, delay in flowering and
accumulation of anthocyanin pigments in MH treated tomatoea
The loss of sensitivity with increasing age in tomato and
other plants in their response to MH has also been re-
ported (13, 19, 44).

Responses of tomato plants to foliar applications of
MH have not been consistent. .The same author working on
one and the same variety of tomato observed at different
times some what different responses. Greulach (19) showed
that the differences in responses he observed in his ex-
periments as well as by others could be possibly due to
the difference in age of the seedlings. It is also possibka
that these varying effects of MH in inducing responses are
due to different degrees of penetration of MH depending

upon the conditions under which eXperiments are carried

out. That relative humidity is a factor which will

-8-

influence rate of absorption of MH by plants has been
known (54).

Roots appear to be more sensitive to applications of
MH than shoots (4). Both stimulation as well as inhibi-
tion of roots have been reported. The concentration of
the chemical is the determining factor in inhibition or
stimulation of roots (3, 4). In corn, foliar applications
of MH at l to 10 p.p.m. stimulated root elongation and at
500 p.p.m it inhibited the roots (9).

Following foliar applications of MH it altered the
color, texture and development of leaves. The leaves be-
came dark green, leathery and brittle and young leaves
failed to expand (4, 18, 20). In certain cases exudates
containing mostly sucrose appear as droplets in MH treated
plants (13).

Flowering in plants is affected by foliar applica-
tions of MK (18, 19, 40, 43, 52). The general tendency of
MH is to induce inhibition of flowering. The induction of
male sterile flowers ensuing MH applications has also been
observed (27). In general MH treatment alters the size,
structure, number and time of anthesis of flowers.

Application of MH as a spray to flowering panicles
of oat at concentrations ranging from 0.03 to 0.75 percent,
has been noted to affect the embryonic development and con-
sequently, the seedlings that arise from such seeds (38).

It can be concluded that applications of MH alters

the growth and development of seedlings. These changes

_ 9 -

resulting in plants by ME treatments are strong indications
that the physiology and metabolism of plants are altered.
The changes induced in the growth and development of seed-
lings by MH, are better understood if one reviews the
changes induced in the anatomy, physiology and chemical

composition of treated plants.

Physiological Changes in Plants Induced_by_MH Application:
The increase in shoot/root ratio following applica-
tion of MB in tomato as well as in other plants have been
reported (19, 20). This suggests imbalance between top
and root growth with the possibility of interference in
translocation and distribution of food material.

MH treated plants reveal alteration in their photo-
synthesis (6), respiration (31), and transpiration (67).
When such processes are affected it has a natural con-
sequence on the metabolism of treated plants.

Naylor and Davis (45, 46), found that MH treated ex-
cised roots of peas, sunflower, tomato, barley, wheat and
cat showed alteration in the respiration. The respiration
rates of the tomato, sunflower, oat, wheat and barley were
more inhibited than in peas or corn. Henderson and Thomas
(26) treated excised stem of pea and sunflower with MH at
concentrations from 800 to 1000 p.p.m. and reported that
oxygen uptake was decreased in pea stems. Low concentra-
tions of MH will stimulate respiration and higher concen-
trations will inhibit it (31).

One of the probable methods by which MH induces

- 10 -

inhibition of plant growth is due to its effects on plant
respiration. When respiration in higher plants is in-
hibited cessation of growth or undesirable morphological
changes may occur (17, 31, 32).

Application of MH increases photosynthetic activity,
which is not always accompanied by increase in dry matter
(6). The increase in photosynthetic activity observed in
plants treated with MH, is attributed to the modification
of the physiology of individual cells as a result of treat-
ment (6).

MH treatment of plants may result in reduced rate of
transpiration as well as uptake of water (40, 55, 67).

Foliar application of MB to plants have influenced
the enzyme systems in them (15, 34). In preparations of
artichoke, cauliflower and pea, applications of MH were
noted to inhibit dehydrogenase activity, both in the
soluble and mitochondrial systems. This indicates that MH
can act on the 48H group of enzymes (15).

Leopold and Klein (37) suggested that MH acts as an
anti-auxin. They found that growth inhibition produced by
low concentrations of MH could be counteracted by addition
of auxin and conversely inhibition of growth by high con-
centrations of auxins relieved by MS. ‘This reversal in
action was independent of pH and furthermore no indication
could be found that MH acted by chemically combining with
the auxin.

0n the whole MH applications result in the alteration

- 11 -

of physiological activities of the plants. The extent
to which they are influenced is dependent on the con-
centration of the chemical, plant species, and environ-

mental conditions.

Agatgmical Changes Induced by MH Applications in Plants:
Foliar applications of MH induce changes in the
anatomy of shoots, roots and leaves (16, 23, 24). The
nature of changes brought about by MH treatments in them
indicates that the inhibition of plant growth following
application is due to inhibition of meristematic activity
and abnormal enlargement of cells. Collapse of phloem
elements, absence of metaxylem and secondary xylems in the
bundles, a general disorganized arrangement of cells, dis-
integration of chloroplasts, abnormal development and de-
generation of stomata and absence of guard cells have all
been observed in MH treated plants (8, 16, 23, 24). The
nature and extent of changes brought about by MH in the
anatomy of shoots and roots are influenced by the con-
centration of the chemical, the treated plant species, and

the stage and development at the time of treatment.

Effect of Foliar Applications of MB on Chemical Com-
pgsition and Mineral Accumulation of Plants:

The effect of foliar applications of MH on chemical
composition of plants have been studied to some extent.
MH treated plants have been observed to show alteration in

carbohydrate, soluble sugars and protein content

'- l2 -

(13, 21, 34, 64, 65, 66, 67). The outstanding effect of
MH applications is the accumulation of carbohydrates and
reduction in proteins.

Uptake and accumulation of nutrient elements ensuing
applications of MH have been studied only to a limited
extent. Peterson and Naylor (49) found that MH treated
tobacco plants had higher calcium and lower phosphorus con-.
tent. Wildon (63) found that a repeat application of
500 p.p.m. solution of MH to tobacco seedlings retarded
accumulation of all major and minor elements in shoots and
roots. Bose (4) treated young tomato seedlings with foliar
sprays of MH at 10, 50 and 100 p.p.m. solution and observed
that uptake of nutrient elements were retarded. Greulach
(22) found while application of growth substances could not
counteract the inhibition in growth induced by MH in sun-
flower, repeated foliar applications of complete nutrient
sprays helped to relieve the inhibition. MH treated plants
often show deficiency symptoms of phosphorus (19, 65) which
indicates that phosphorus uptake may be affected.

From the few published reports on accumulation of
nutrient elements in MR treated plants it is evident that
roots are unable to take up from the media effectively the
nutrient elements needed by the plants. Since uptake of
nutrient elements are influenced by treatment, it is con-
ceivable that some of the changes in growth responses wit-
nessed in MR treated plants could also be secondary effects

not attributable to the chemical alone. Furthermore,

- 13 -

applications of MH will influence factors associated with
absorption of nutrient elements, particularly permeability
of membrane, osmotic pressure and exchange capacity of

roots.

MATERIALS AND METHODS

Greenhouse experiments were conducted from the fall

of 1958 to the spring of 1960, to study some of the physio-

logical responses of tomato following foliar applications

of MH. Among the responses studied, fruit-set in tomato

under high night temperature, as influenced by such applica-

tions was of particular interest. Other studies were the

following:

General growth responses resulting from
foliar applications of maleic hydrazide.
Accumulation of certain nutrient elements
of interest in maleic hydrazide treated
plants. ‘

Rate and total accumulation of phosphorus
in maleic hydrazide treated plants grown
in a nutrient culture with varying levels
of phosphorus.

Respiration of roots as influenced by foliar

applications of maleic hydrazide.

-14-

15 -

Cultural Proceduge:

The two tomato varieties used in the experiments
were John.Baer and Michigan Ohio Hybrid. The former was
utilized particularly in the experiments related to fruit-
set under high night temperature, and in experiments per-
taining to growth responses, and accumulation of certain
nutrient elements of importance. John Baer was chosen be-
cause it can better withstand the high night temperature
ranges (70O - 80°F) in the experiments (36). The latter,
Michigan Ohio Hybrid, was used in experiments related to
rate and total accumulation of phosphorus and respiration
of roots following foliar applications of maleic hydrazide;
since selection of more uniform seedlings was possible in
this variety than in John Beer.

In all the experiments seeds were sown in soil con-
tained in wooden flats which were placed on greenhouse
bench. The seedlings were subsequently selected for
uniformity and planted to pots of the required size con-
taining either sand or greenhouse soil as desired. The
selection for uniformity was based on height and leaf
length of seedlings. A further elimination of seedlings
that were not uniform was also made before applications
of MH. Thus variation due to size and age of seedlings was
reduced.

Plants were watered daily with measured quantity of
water. The seedlings were given nutrient solutions as

needed. Half molar stock solutions of calcium nitrate,

-16-

magnesium sulfate, and potassium dihydrogen phosphate were
first prepared. The final nutrient solution was prepared
by utilizing nine milliliters of each of the half molar
solutions per liter of water. Each seedling received
250 milliliters of the nutrient solution during its early
stage of growth. The amount used was raised to 500 mil-
liliters at a later stage of its development. Seedlings
grown in pots filled with fine sand received their nutrient
solutions On alternate days, whereas seedlings grown in
pots filled with greenhouse soil received the nutrient
solution once a week. ,In the nutrient culture experiment
related to rate and total uptake of phosphorus by tomato
seedlings treated with MH,when grown under varying levels
of phosphorus with all other nutrients at the same level,
a different solution and procedure was adopted. This is
described in the latter part of 'material and methods'
given for individual experiments.

MH was available as a‘30 percent diethanolamine salt.
From this stock solution, a 1000 p.p.m. solution of MH
was prepared in distilled water and was subsequently used
for the preparation of other concentrations. All applica-
tions of MH were made as foliar sprays until the leaves
were completely saturated with the solution. When MH
was applied, the soil and the flower clusters,if any,were
covered with polyethylene sheets to prevent contact with
the chemical sprays.

The growth regulator used in the fruit-set experiment

- 17 -

wasflnaphthoxyacetic acid (BNOA) and was applied as an
aqueous spray at 50 p.p.m. solution to only the fully
Opened flowers.

All the experiments were conducted at temperatures,
ranging from 700 - 80°F, utilizing the natural photOperiods
available during the seasons in which they were carried
out. Conditions related to experiments on fruit-set de-
serve an additional mention. These experiments were con-
ducted during winter and early spring when it was possible
to maintain the high night temperatures required. Special
attention was paid to keep the night temperature at
70° - 80°F. The average length of the day, during the
period of these experiments, ranged between 9 to 10 hours.
The temperature ranges maintained in this experiment, par-
ticularly the high night temperature, is high for any
variety of tomato (62). Since conditions related to the
experiments were not available in the field, experiments

had to be confined to the greenhouse.

Sampling_Methods and Procedures Used in the Analysis of

Plant Materials:

Wherever plant samples were collected for purposes
of analysis,the following general procedure was adOpted:
The plants were removed carefully from the pots in such
a manner as to permit maximum possible retention of roots.
The the above ground portions and roots were separated.

The roots were washed repeatedly with water to remove all

the soil particles, and at the same time only minimum loss

-18-

of roots was allowed. Then the roots were carefully
blotted to remove as much of the moisture as possible. The
shoots and roots were transferred into paper bags, properly
labelled, to permit each treatment as well as roots and
shoots in each treatment, being maintained separately. These
were then.dried in an oven kept at 70°C, for three days.
After recording their dry weights, they were ground, and
kept in well stoppered bOttles. The bottles in turn were

maintained in the dessicators until the samples were needed
for analysis.

Spectrographic and chemical methods were used to de-
termine the nutrient elements. Nitrogen was estimated by
Kjeldahl's method, potassium by flame photometric methods
(1), calcium, magnesium, phosphorus, manganese, boron and
cOpper by spectrographic methods, (11). Phosphorus, in one
of the experiments (experiment IV) was determined by de-
veloping molybdenum blue color on the plant extract obtained
by wet ashing with nitric acid and perchloric acid methods
as described by Piper (50).

The above procedure is a broad outline of general
materials and methods used in these experiments. Addi-
tional details for individual experiments, wherever nec-

essary are provided separately.

I. Experiments on fruit-get in tomato grown under high
night temperature, 700 - 80°F:
Two experiments were designed during 1958 - 1959,
in an effort to determine the effect of foliar applications

- 19 -

of MB on fruit-set in tomato grown under high night tem-
perature, 70° - 80°F. Seedlings were grown in eight-inch
pots filled with greenhouse soil, one seedling per pot.

Each of these experiments included the following
four major groups of treatments:

a. Foliar applications of MH at the time the
first flower in the first cluster started
to Open

b. An aqueous spray of BNOA to fully opened
flowers

c. Combination of MH and BNOA

d. Control

The control plants indicate the effect of high night

temperature on fruit-set as well as provide comparisons for
other treatments.

The general design of the experiments provided for
replications and randomizations of treatments. Each single
plant in a pot was considered as a replicate. Based on the
number Of flowers taken for each treatment, flower abscis-
sion and fruit-set were expressed as a percentage. When-
ever comparisons Of treatments for evaluating fruit-set was
required, a 't' test was run.

The first experiment was conducted between November,
1958, to February, 1959 (winter), and the second experiment
was between February to April, 1959 (early spring). The
average length of the day, and light intensities in ex-

periment 1, were comparatively less than in experiment 2.

-20-

The number of plants and flowers utilized for the
treatments in both the experiments are shown in Table 1.

Applications of foliar sprays of MH, in experiment 1,
were made on January 7th, 1959, when the first flowers
started to Open. In experiment 2, similarly applications

of HR were conducted on April 3rd, 1959.

II. Experiments related to general growth responses of
tomato to foliar applications of MH:

The growth responses of tomato as affected by foliar
applications of MH, was determined during summer 1959. On
June 20th, 1959, the tomato seedlings growing in eight-inch
pots filled with fine sand were separated into four groups.
Each pot contained a 47 day old seedling and solutions Of MS
was applied as a foliar spray at concentrations of 10, 100
and 1000 p.p.m. Non-treated plants served as the control.
Each single plant in a pot was considered a replicate and
15 seedlings were alloted for each treatment. The treat-
ments were then randomized on the greenhouse benches.

Following applications, periodic Observations were
made for the length of the stem, stem diameter, number of
leaves, length Of the largest leaf, length of flower clus-
ters, and number of flowers and green buds produced in all
the treatments. The activity of the terminal meristem of
the shoot, color, texture and venation of the leaves were
also recorded. For examination of roots some plants were

removed from each treatment periodically. The total number

of such plants removed were three per treatment.

- 21 -

Table I: Number of Plants and Flowers Utilized in
Experiments Related to Fruit-Set in Tomato
(John Bagr),Under High Night Tegperature

Experiment 1:

 

 

 

Treatments* Number of plants Number of flowers
per treatment per treatment
Group I (MH) 44 156
a. 10 p.p.m. 14 51
b. 20 p.p.m. 14 50
c. 40 p.p.m. 16 55
Group II (BNOA) lg 22
Group III (MH + BNOA) 48 152
a. MH 10 p.p.m. + BNOA 16 53
b. MR 20 p.p.m. + BNOA 16 54
c. MR 40 p.p.m. + BNOA 16 52
Group IV (Control) ;§, 54

 

Experiment 2:

 

 

 

Treatments* Number of plants Number of flowers
P9P treatment per treatment

Group I (MR) 16 58

Group II (BNOA) 8 28

Grgup III (MH + BNOA) 16 55

Group IV (Control) 8 32

 

*Treatments: (MH) as a foliar spray; (BNOA) as an aqueous
spray to fully Opened flowers: (MH + BNOA) as their

cOpbinations. In Experiment 2, MH was used at 20 p.p.m.
on y.

-22-

The experiment was terminated on July 20th, one month
after application of MH,when the control flowered. The
plants were harvested and six plants from each treatment
were removed for subsequent analysis, to determine the

amounts of nutrient elements of interest.

III. Experiments related to determinations of nutrient
elements of interest in MB treated plants:

Tomato seedlings, six each per treatment, removed
from the previous experiment on July 20th, 1959, provided
the samples needed for analysis. The methods of collecting
samples and procedures of determining the nutrient elements
have already been mentioned (p. 17-18). The following
nutrient elements were determined: Nitrogen, potassium,
phosphorus, calcium, magnesium, boron, manganese, and
copper.

The accumulation of each nutrient element in the
various treatments was determined by the following formula:

Amount Of nutrient _ Av. dry weight of plant X Av.% mineral
element per plant ’ 100 _
IV. Experiment concerning rate and total accumulation of

phogphorus in NH treated tomatogplants grown in a

nutrient culture with varying levels of phosphorus:

 

In a nutrient culture, by maintaining all other nu-
trients except phosphorus at the same level, the rate and
accumulation of phosphorus in MR treated plants as compared

to non-treated plants growing under similar conditions were

studied. The levels of phosphorus in the experiments were

- 23 -

16, 32, 64 and 128 p.p.m.

Tomato seedlings were grown in one gallon glazed pots
containing the nutrient solutions. Provisions were made
for maintaining equal volumes of nutrient solutions in all
pots as well as for having regulated air supply. Each pot
accomodated four tomato seedlings.

The design of the experiment provided for replications.
For each level of phosphorus, six pots were alloted. Out of
this, in each level of phosphorus, seedlings in three pots
were used for MH treatments. Thus 12 seedlings for each
level of phosphorus were treated with MH, and 12 were left
non-treated. Each single seedling was considered as a
replicate.

On December 6th, 1959, when seedlings were 30 days
old, two seedlings were removed from each pot for each
level of phosphorus present,at the time of application of
MH. On January 3rd, 1960, all seedlings were removed from
all the treatments for final determinations of phosphorus.

Besides determining the amounts of phosphorus, Ob-
servations were made on the general condition and appearance
of plants.

The nutrient solutions used in the experiment for
providing the desired levels of phosphorus are shown in
Table 2.

The preparation of nutrient solutions was a modifica-
tion of one suggested by Meyer (39).

Nutrient solutions were changed once a week.

-24-

Table 2. Propprtion of One Molar Salt Solutions Required

to Make Up 18 Liters of Final Nutriept Solutions:

 

 

Level of KNO KH P0 Ca(N0 ) MgSO K01 NaH PO
Phosphorus 3 2 4 3 2 4 2 4
16 p.p.m. 36 m1. 9 ml. 54 ml. 36 ml. 27 ml. ml,
32 p.p.m. 36 " 18 " 54 n 36 n 18 n n
64 p.p.m. 36 " 36 u 54 n 36 n —" u

128 p.p.m. 36 " 36 " .54 " 36 " ___" 36 "

 

To 18 liters Of completed solution, 18 ml. Of ferric
tartarate and 18 ml. of minor element solutions were added.

Preparation of Minor Element Solution:

~H3B03 5 grams
II
Mn012.2H20 3.6
Zn012 0.2 "
' N
CuCl2.2H20 0.1
MOO3 0.15 "

All were dissolved in two liters of distilled water.

V. Experiments relgted to influence of foliar applications
of MH on root hairs and respiration of roots:

The influence Of foliar applications of MN on respira-
tion of roots were studied. For this purpose tomato seed-
lings were grown in four-inch pots filled with fine sand.
Solutions of MH was applied as a foliar spray at 1000 p.p.m.
when the seedlings were one month old. Each pot contained

one seedling. Following application of MH, root tips were

removed at needed intervals for determination Of rates of

- 25 -

respiration. A group of non-treated plants were used as
control for comparative measurements.

Oxygen uptake was determined by Warburg Respirometer
by using standard manometric techniques (56). An initial
trial determination showed that 20 root tips of 1 cm. length
each, collected from six plants, per flask was adequate for
measuring oxygen uptake. Root tips from MH treated plants
could not be used for more than one hour in the determina-
tion results. Each treatment was duplicated and the amount
of oxygen utilized was recorded in microliters per milli-
gram dry weight of root tips. Root tips for final deter-
minations were collected 192 hours after application of MH.

A group of tomato seedlings grown in sphagnum moss,
soaked in nutrient solutions and kept wrapped in poly-
ethylene sheets were used for studying the influence Of MH
on root hairs.

Out of the 24 seedlings grown in this manner, half
of them were treated with solutions of MH, applied as a
foliar spray at 1000 p.p.m. The seedlings were one month
old at the time of treatment. Ensuing application the
nature of root hairs formed was carefully Observed period-
ically.

Since the seedlings were wrapped in polyethylene
sheets, it was easy to unwrap the sheets and Observe the
root hair development without removing and disturbing the
seedlings. After an examination they were wrapped up again

and this permitted observation on the same seedlings each

time.

RESULTS

I. i - et n m t e r wn un er i
temperatppe (70o - 80°F) as influenced by fplipp
applications of maleic hydrazide, growth regulator
treatment to fully Opened flowers and Their Combinations:

Tomatoes grown under high night temperature produced
fewer flowers per cluster. On an average each plant had
3.4 to 3.6 flowers per cluster, (Appendix Table 1). Sub-
sequent to flowering, abscission of flowers was recorded to
be high (Tables I, II). All these resulted in poor or no
fruit-set (Tables I, II, Figure 1).

Under this condition, foliar applications of maleic
hydrazide combined with growth regulator treatment to fully
Opened flowers improved fruit-set (Tables I, II). The in-
crease in fruit-set noted in this treatment as compared to
the control, was significant at the 1% level (Table II A).
Neither applications of foliar sprays Of maleic hydrazide,
nor treatment of fully opened flowers with growth regulator
alone, resulted in significantly better fruit-set than the
control, (Table II A).

It was observed that whenever applications of maleic
hydrazide was combined with growth regulator treatment,
besides the terminal flower, other flowers developed into

fruits.
-26..

- 27

Table I: Influence of Foliar Applications of Maleic Hydra-
zide, Growth Regulator Treatment to Fully Opened Flowers,
and Their Combinations, on Flower Abscission and Fruit-Set
in Tomato (John Baer), When Grown Under High Night Tem-
perature (700- 80°F). Experiments Conducted During November,
1958 to February, 1959.

 

 

 

Treatments* Flower Abscission Fruit-Set
in percentage in percentage
I. Control 100 0
II. BNOA 96.87 3.13
III. MH - 10 p.p.m. 100 0
MH - 20 p.p.m. 100 0
MH - 40 p.p.m. 100 v 0
IV. MH - IO p.p.m. + BNOA 94.34 5.65
MH - 20 p.p.m. + BNOA 90.74 9.26
MH - 40 p.p.m. + BNOA 96.15 3.85

 

 

*Treatment symbols: MH - Maleic Hydrazide
BNOA - ,9 naphthozyacetic acid as
an aqueous spray at 50 p.p.m.

MH + BNOA - Combinations

-28-

Table II: Influence of Foliar Applications of Maleic
Hydrazide, Growth Regulator Treatment to Fully Opened
Flowers, and Their Combinations, on Flower Abscission and
Fruit-Set in Tomato (John Baer) When Grown Under High Night
Temperature ( 7Oo - 80°F). Experiments Conducted During
February to May, 1959.

 

 

t
Treatments . Flower Abscission Fruit-Set
in percentage in percentage

I. Control 90.62 9.38
II.. BNOA ‘ 85.71 14.29
III. MH - 2O p.p.m. ‘ 75.69 24.31
IV. MH - 20 p.p.m. + BNOA 65.82 34.18

 

Table II A: Comparison Of Data Obtained on Fruit-Set
(in Table II) For Statistical Significance.

 

 

 

Treatments Compared ‘ 't' Distribution
I. Control vs BNOA 0.59
II. Control vs MH 1.96
III. Control vs MH + BNOA 3.30**
Iv. MH + BNOA vs BNOA 2.16*
V. MH + BNOA Vs MH 1.16
1;_1 .

Significant at 1% level'
* Significant at 5% level

I
Treatment symbols:

MH - Maleic hydrazide; BNOA - I? naphthoxyacetic acid;
MH + BNOA - Combinations.

- aq-

3017mm : I

Fruit-set in tomato (John Baer) grown under high night
temperature (700 - 80°F) as influenced by applications of

growth regulator to fully Opened flowers, and combined
treatments of foliar applications of maleic hydrazide and
growth regulator.
Upper:

Left to right: Control, growth regulator alone and

combination of growth regulator and maleic hydrazide.

(Note the lack of fruits in control, only the terminal
flower developing into fruit in growth regulator treat-

ment and in combined treatments of maleic hydrazide and
growth regulator, besides the terminal flower other flowers

also developing into fruits.)

Lower: A group of fruits obtained by the combined treat-
ments of maleic hydrazide as a foliar spray and

growth regulator to fully opened flowers.

 

 

- 30 -

In other treatments whenever fruits set, it was always the
terminal flower which develOped into fruit (Figure 1).

In experiment 2, which was conducted during February
to May 1959. better fruit-set was recorded for all the
treatments as compared to experiment 1, which was carried
out between November 1958 to February 1959. In the former
better light intensities as well as longer days existed

as compared to the latter.

II. ~szsiological resppnses of tomato as influenced by

foliar applications Of maleic hydrazide:

A. General Growth Responses:

Foliar applications of maleic hydrazide to young to-
mato plants (John Baer) resulted in the alteration Of their
growth and development. The growth responses elicited by
such applications indicated that treatment with maleic
hydrazide sprays will induce inhibition of plant growth.
The chief responses Observed were:

1. Rate of stem elongation was retarded.

2. Stem diameter was increased.

3. The number of leaves per plant were reduced.
4. The length of the leaf was shortened.

5. The color, texture, and venation of leaves

were altered, i.e. the leaves dark green,

leathery and brittle and venation less
prominent.

6. Root elongation was inhibited and fewer

root-hairs develOped.

- 31 -

The extent to which changes were brought about by
applications of maleic hydrazide in tomato seedlings, were
influenced by the concentration Of the chemical.

The total amount of growth made by the stem in maleic
hydrazide treated plants and the control, from the time of
application of the sprays to the end of the experiment is
shown in Graph 1. With increasing concentrations Of maleic
hydrazide, the rate of stem elongation decreased. The con-
trol plants had the maximum elongation of stem.

The lowest concentration used (10 p.p.m. solution) had
the least effect on the appearance and growth of plants.
Plants treated with 10 p.p.m. solutions of maleic hydra-
zide sprays resembled the control (untreated) in almost
every respect. Growth measurements made (Table III) in
plants treated with 10 p.p.m. solutions were compared with
those of untreated plants, statistically. Except for shoot
weights the other growth measurements did not show any sig-
nificant differences as compared to the control. The re-
duction in shoot weights was significant at the 1% level.

Plants sprayed with 100 p.p.m. solutions of maleic
hydrazide as compared to the control revealed that the
differences between them for the following growth measure-
ments (Table III) were significant at the 1% level:

a. Height 7
b. Stem diameter

c. Number of leaves per plant
d. Dry weights of shoots.

—-32."

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- 33 -

Table III: Growth Measurements of Tomato (John Baer) as
Influenced by Varying Concentrations of Maleic Hydrazide,
When Applications were Made as a Foliar Spray to 47 Days
Old Seedlings:

 

 

 

Measupe- _’_ Treatments ‘E;S;Eée;%:
ments Control 10p.p.m. 100p.p.m. 1000p.p.m. 5% 1%
1. Height 30.11 28.57 26.85 24.40 1.45 2.00
(in one)
2. Stem
Diameter 5.18 5.15 6.70 5.95 0.47 0.67
(in mm)
3. Number Of
Leaves 8.00 7.57 7.50 5.33 0.27 0.37

(per plant)

4. Length of
the Largest
Leaf 22.00 20.93 20.50 16.48 1.41 1.88
(in one)

5. Dry Weights
(1n ems)

8.. Shoots 4.08 3050 3030 3.13 0.36 0.49
b. Roots 1.55 1.30 1.05 0.95 0.84 1.16

6. Length of
the Flower .
Stalk 2.48 1.87 ' 1.47 , O 1.03 1.06
(in cms)

7. Number Of .
Open Flowers

and Green Not
Buds 3.67 2.67 2.00 0 Significant
(per plant)

8. Shoot/Root

 

it
All measurements were taken one month after application
and from six replications per treatment.

-54.-

Féfluve : Z.

F104 C at
D

Alteration in appearance, growth and development of
Tomato Seedlings as a result of foliar applications

of solutions of maleic hydrazide at 1000 p.p.m.

Left: Control Rigpt: Treated

(Note the reduction in height, number of leaves and

activity of lateral buds in treated plants.)

Applications of solutions of maleic hydrazide were carried
out at a time when seedlings were 47 days Old. Photo-

graphs taken one month after application.

 

ch u we '.

Foliar applications of solutions of maleic hydrazide to
young tomato seedlings at 1000 p.p.m. resulted in injury

to the apical meristem of shoot, malformation Of leaves

arising from such meristem and inhibition of flowering.

Upper: Control plants showing normal activity of terminal
meristem of the shoot, normal leaves and flower

buds.

Lower: Plants treated with solutions of 1000 p.p.m. maleic

hydrazide showing injury to the terminal meristem,

malformed leaves and inhibition of flowering.

Solutions of maleic hydrazide were applied as a foliar

spray to 47 day old seedlings of tomato and photographs

were taken one month after application.

 

-35-

Plants receiving 1000 p.p.m. solutions of maleic hydrazide
as a foliar spray were distinctly different in appearance
from that of the control and other treated plants (Figure 21
The terminal meristem of the shoot was most severely affect-
ed in these plants. The leaves arising from the terminal
meristem were malformed and showed signs of injury. The
lateral buds were activated and flowering was inhibited.

NO signs of flower buds could be detected by a visual ob-
servation (Figure 3).

The growth measurements taken in plants treated with
solutions of maleic hydrazide at 1000 p.p.m. were compared
with those of the control. Except for the dry root weights,
the differences between them for all the growth measure-
ments were significant at the 1% level (Table III).

The differences in the growth measurements between
treated plants, when statistically evaluated indicated the
following:

1. The differences in height, stem diameter,
number of leaves per plant and the length of
the largest leaf, between plants treated with
1000 p.p.m. solutions of MH and plants treated
with other concentrations were significant

at the 1% level.

2. Plants treated with 100 p.p.m. solutions of
MH as compared to plants treated with

10 p.p.m. solutions of MH had a significantly

increased stem diameter and reduced height.

- 37 -

Differences between them for other growth
measurements made and compared were not

significant.

B. Nutrient e1ement_gontents:

The contents of some nutrient elements of maleic
hydrazide treated and control plants, determined one month
after application of the chemical are presented in Table IN
The nutrient elements are expressed as a percentage as well
as in grams or milligrams as the case may be, based on the
dry weights of plants. (For dry weights, Appendix Table 2%
All comparisonsbetween treatments are made on data expressed
on dry weight basis of plants. The indications are that
maleic hydrazide treated plants show a tendency for lesser
accumulation of nutrient elements as compared to the con-
trol.

Among the treated plants the tendency for accumula-
tion of nutrient elements were:

1. In so far as the roots were concerned, all
the treated plants for all the nutrient ele-
ments determined, showed a tendency towards
a decreased amount of accumulation with in-
creasing concentration of the chemical.

2. In shoots such a tendency was observed only
for boron.

3. The combined amounts of nutrient elements of

shoots and roots indicated for potassium,

phosphorus, boron and manganese, the contents

-38—

Table IV: Some Nutrient Element Contents in Shoots and
Roots of Tomato, Determined One Month After Application of
Maleic Hydrazide. Applications Made as a Foliar Spray to

47 Day Old Seedlings:

 

 

 

Table continued next page.

' Total
nutrient -----.---§1;129§§-..--- ...... R002 8 ---
Elements % Weight 1 ‘31653 Régfigftfitf

basis basis basis
NITROGEN
Control 1.29 52.63 1.14 17.67 70.30
MH - 1 1.24 43.40 1.47 19.11 62. 51
MH - 2 1.13 37.29 1.50 15: 75 53.04
POTASSIUM
Control 3.50 142.80 2.75 42.63 185.43
MH - 1 3.30 115.50 2.50 32.50 148.00
MB - 2 3.14 103.62 2.58 27.09 130.71.
CALCIUM
Control 2.07 84.46 1.16 17.98 102.44
MR " 1 2003 71005 1023 15099 87004
MAGNESIUM
Control 0.62 25.30 0.69 10.70 36.00
MH - 1 0.57 19.95 0.71 9. 36 29. 31
us - 3 0.79 24.73 0.60 5.70 30. 43
PHOSPHORUS
Control 0.23 9.38 0.30 4.65 14.03
"H ' 1 0020 7000 0029 3077 10077
MR - 2 0022 7026 0.29 3005 10031
MB " 3 0023 7020 0026 2047 9067

- 39 -

Table IV (Continued)

 

 

Nutrient T°t31

 

 

""""""""""""""" ‘“""“‘ (Shoots +

Elements % gzޤgt % g;: at Roots, wt.
basis

BORON

Control 0.0027 110.16 0.0028 43.40 153.56

MH - 1 0.0025 87.38 0.0021 2 .30 114.80

MH - 2 0.0026 85. 0.0023 2 .15 109.95

MB - 3 0.0027 84.51 0.0021 19.95 104.46

MANGANESE

Control 0.0035 142.80 0.0053 82.15 224.95

MH - 2 0.0031 102.30 0.0040 42.00 144.30

MH - 3 0.0032 100.16 0.0039 37.05 137.21

COPPER

Control 0.0027 110.16 0.0054 83.70 193.86

MH - 1 0.0022 77.00 0.0048 62.40 139.40

MH - 2 0.0021 69.30 0.0042 44.10 113.40

MH - Maleic hydrazide

“H - 1, at 10 popeme

MH - 2, at 100 p.p.m.

NH - 3, at 1000 pepomo

Nitrogen, Potassium, Calcium, Magnesium and Phosphorus
expressed in milligrams.
expressed in micrograms.

Boron, Manganese and Copper

-40-

decreased with increase in concentration of

maleic hydrazide.

C. Rate and_total accumulation of phosphoru :
Applications of solutions of maleic hydrazide as a

 

foliar spray at 1000 p.p.m. to tomato plants grown in a
nutrient culture with varying levels of phosphorus resulted
in reduced uptake and’accumulation of phosphorus (Table V).
Table V: Rate and Total Accumulation of Phosphorus in
Tomato (Michigan Ohio Hybrid) When Grown Under varying
Levels of Phosphorus in a Nutrient Culture, With and With-
out Maleic Hydrazide. Maleic Hydrazide Applied as a Foliar

Spray When Seedlings were 30 Days Old:

 

 

 

 

 

Level Total Accumulation Rate of Efficiency
of 'P' of 'P' (in mgs) Accumulation of Accumulation
in of 'P' (mgs) as a percentage
p.p.m. of Control
(“Control Treated Control Treated Control Treated
16 19.14 13.20 17.14 11.20 100 65.34
32 26.42 22.46 23.66 19.70 100 83.26
64 35.66 27.84 30.26 22.44 100 74.15
128 46.00 32.00 40.32 26.32 100 65.33
OP!

- Phosphorus.

The efficiency of accumulation of phosphorus in

treated plants ranged between 65.33 to 83.26 percent and

-41..

was influenced by the level of phosphorus in the nutrient

culture. In both the control and treated plants, the rate

and total accumulation of phosphorus increased with the

increase in level of phosphorus in the nutrient culture

(Table V).

Observations made on the growth and develOpment of

the tomato seedlings in the same experiment indicated the

following:
1.

With decrease in level of phosphorus in the
nutrient culture, the length of the roots
decreased. With application of maleic hydra-
zide as a foliar spray this was further in-
hibited (Figure 4).

Shoot growth was also inhibited in tomato
seedling irrespective of level of phosphorus
in the nutrient culture as a result of
application of maleic hydrazide (Figure 5).
The most pronounced effect of maleic hydra-
zide was seen on the leaves in all the seed-
lings in all the levels of phosphorus. The
number of leaves per plant was reduced. The
color, texture, margin of leaves and venation
were also influenced. Leaves were dark green,
leathery and brittle. Venation was less prom-
inent and the axillary angles that leaves
made with the stem were narrower, as compared

to the controls (Figure 5).

[*éq (1Y8 :

-41.

4.

[jg/3:176, L’.

U

Decrease in length of roots in tomato seedlings with de-
crease in level of phosphorus in the nutrient culture.
With foliar applications of solutions of maleic hydrazide

at 1000 p.p.m. this was further inhibited.

Roots from treated plants alternated with their controls.

Left extreme is the control seedlings grown in 128 p.p.m.
level of phosphorus showing the root growth. They are
followed by seedlings grown in 64 and 16 p.p.m. levels of

phosphorus.

Applications of solutions of maleic hydrazide were carried
out when tomato seedlings were 30 days old and photographs

taken 28 days after application.

 

thure: 0

F‘ (- blitz!
U

ad

Foliar applications of solutions of maleic hydrazide at

1000 p.p.m. to young tomato seedlings growing in a nutrient

culture with varying levels of phosphorus resulted in

inhibition of shoot growth and alteration in color, texture,

lobing of margin, venation and orientation of leaves to the

stem.

Upper:

Lower:

Treated tomato seedlings in all levels of phosphorus
showing inhibition of shoot growth. Treated plants
alternated with controls. Left extreme is the con-
trol seedling growing in 16 p.p.m. level of phos-
phorus. It is followed by seedlings grown in 64

and 128 p.p.m. level of phosphorus.

A comparison of treated plants with the control for

showing the difference in number of leaves,lobing

of margins and orientation of leaves with the stem.

Left: Treated Right: Control

Photographs were taken 28 days after application of

solutions of maleic hydrazide at 1000 p.p.m. to 30 day

old seedlings.

 

- 44 -

It was evident from the observations made that maleic
hydrazide applications as a foliar spray resulted in the
inhibition of growth of young tomato seedlings. Further-
more, by increasing the level of phosphorus in the nutrient
culture, it was not possible to relieve completely the in-
hibition induced by maleic hydrazide.
D-WWW

respiration of roots in tomato:

When solutions of maleic hydrazide were applied as a
foliar spray at 1000 p.p.m. to one month old tomato seed-
lings, the development of root-hairs and respiration of
roots were influenced. Following application, examination
of plants made within a week revealed that root-hairs in
treated plants were few and they had a tendency to be lo-
cated near the tip of the roots. Rates of respiration in
treated root tips determined 192 hours after application
of the chemical as compared to the root tips of non-treated
plants, showed a marked reduction (Table VI, Appendix
Table 4).

Table VI: Respiration of Roots in Tomato (Michigan Ohio Hy-
brid) as Influenced by Foliar Applications of Maleic Hydra-
zide. Applications Made When Seedlings Were 30 Days Old:

 

 

 

Treatments . Oxygen Consumed
(in microliters/milligram
dry weight)
1. Control . 9.04
2. Treated 1.30

 

*192 hours after application of maleic hydrazide:

DISCUSSION

Fruit-Set in Tomato (John Baer) Grown Under High Night
Temperature:

When tomatoes are grown under night temperatures
higher than optimal for their growth, they are subjected
to an unfavorable environment. Under this condition, veg-
etative growth becomes dominant, fewer flowers are produced,
and flower abscission is excessively high. All these result
in poor or no fruit-set (62). Such was the case in the
present experiments also, when tomatoes (John Baer) were
grown under high night temperature, 700 - 80°F (Tables I,
II).

Under the aforesaid condition, independent foliar
applications of maleic hydrazide or growth regulator treat-
ment to fully opened flowers fail to increase fruit-set,
but their combinations resulted in significant increase of
fruit-set (Tables II, IIA). The indications of these re-
sults are best appraised in the light of factors associated
with fruit-set under high night temperature in tomato.
According to Went (62) the crux of the fruit-set problem in
tomato under high night temperature lies in the critical
availability of carbohydrates and the manner in which it is

subsequently utilized. The poor fruit-set under this

-45-

-45'.

condition arises out of the available carbohydrates being
made use of in an excessive vegetative growth to the

detriment of fruit-set (62). By reducing vegetative

growth, accumulation of carbohydrates is favored which im-
proves fruit-set. Applications of maleic hydrazide result
in the reduction of vegetative growth, retardation of res-
piration and accumulation of carbohydrates in many plants.
Since applications of maleic hydratzide alone did not re-
sult in better fruit-set, there are two possible explana-
tions. One is, the application of maleic hydrazie failed
to reduce vegetative growth and increase carbohydrate
accumulation adequately. The second reason is that, besides
deficiency of carbohydrates some other secondary factor is
involved. Growth regulator applications are often known
to improve fruit-set where failure of pollination exists
(48). Since combined treatments of maleic hydrazide and
growth regulator have been shown to increase fruit-set, it
is surmised that under high night temperature besides lack
of adequate availability of carbohydrates, failure of
pollination also exists. Howlett (29, 30) has reported
that the deficiency of carbohydrates in tomatoes, induces

pollon sterility.
Foliar applications of maleic hydrazide combined with

growth regulator treatment, gave significantly better
fruit-set as compared to growth regulator treatment alone,
(Tables II, IIA). Failure of pollination has been in-

dicated to be a secondary factor associated with high night

-47-

temperature. Then it is only reasonable to attribute a
greater significance to the foliar applications of maleic
hydrazide for the increased fruit-set recorded in the ex-
periment. Hence the indications are that maleic hydrazide
can be used to counteract the unfavorable influence of
high night temperature. Foliar applications of solutions
of maleic hydrazide at 2000 p.p.m. to citrus seedlings
helped them to withstand as low a temperature as 22°F (68).
The principle was to provide for the accumulation of car-
bohydrates to overcome the effects of low temperatures.
Learner and Wittwer (35), making soil applications of
maleic hydrazide to young tomato transplants concluded that
the chief objection in using this chemical for hardening
practices was that it reduced early yields. Roots are more
sensitive than shoots in their response to maleic hydra-
zide and treatment of young seedlings are known to result
in undesirable morphological changes (4, 9, 31). This in-
dicates that the time and method of applications of maleic
hydrazide are important when used for hardening practices.
In the present experiments maleic hydrazide was used as a
foliar spray after the plants started to flower. The
flower clusters as well as the soil were protected from the

chemical sprays.

Physiological Rgsponses of Tomato Seedlings to Foliar

Applications of Maleic Hydrazide:
When young tomato seedlings were treated with foliar

 

sprays of maleic hydrazide their growth and development

-48-

were altered. The extent to which they were influenced
depended upon the concentrations of the chemical used. At
the highest concentration (1000 p.p.m. solutions), both veg-
etative and reproductive growth were affected (Table III,
Figures 2,3). At higher concentrations the chemical induced
inhibition of growth. These observations are in agreement
with those of others who have reported on inhibition of
plant growth in tomato and other plants ensuing foliar
applications of maleic hydrazide (l2, 13, 18, 44, 53).

The external changes observed in growth and develop-
ment of tomato seedlings fellowing foliar applications of
maleic hydrazide are possibly the relfections of alteration
in their physiological activity. Such an assumption
appears to be logical when the accumulation of nutrient
element, root growth, extent and nature of root hairs and
root tips present and respiration of roots in treated
plants are all considered.

Following foliar applications of maleic hydrazide in
tomatoes the root elongation was inhibited, and the root
tips were found to show injuries as well as necrosis. The
roots were shorter and fewer as compared to the non-treated
plants. The chemical appeared to act as a root pruning
agent. Root pruning is known to produce vegetative growth
and favor accumulation of carbohydrates (82). One of the
probable reasons for inhibition of vegetative growth and
accumulation of carbohydrates in maleic hydrazide treated

plants, which has been frequently reported, could be due

- 49 -

to its effect on the root tips and roots in general.

Maleic hydrazide treated plants were found to have
fewer root hairs as compared to the non-treated plants.
The root hairs instead of being present a few millimeters
behind the root tips in the 'zone of maturation', appeared
at the very tip of the roots. Either the region of elonga-
tion was reduced to such an extent as to make the root
hairs in the 'zone of maturation' come closer to the root
tips or the location of root hairs were possibly altered.

The root hairs play a vital role in the absorption
of water and the nutrient elements. When the number and
location of root hairs appeared to be altered, it is con-
ceivable that the uptake of nutrient elements could be
affected. The experiments on the accumulation of some
important nutrient elements following foliar applications
of maleic hydrazide to the tomato plants showed that they
accumulated lesser amounts of nitrogen, potassium, phos-
phorus, magnesium, boron, maganese and copper as compared
to the non-treated plants (Table IV).

Reduced accumulation of nutrient elements observed
in the treated plants in the present experiments can be
considered to reflect the efficiency of uptake of nutrients
by the roots, from the media. It then suggests that fac-
tors associated with the absorption of nutrients, such as
membrane permeability, osmotic pressure and exchange ca-
pacity of the roots are likely to be influenced.

Since uptake of nutrient elements are affected by

- 50 -

treatment with maleic hydrazide, some of the growth re-
sponses resulting by its application could be secondary
effects not attributable to the chemical alone.

Foliar sprays of maleic hydrazide to the tomato
plants grown in a nutrient culture, with varying levels
of phosphorus, have shown that the efficiency of uptake,
the rate and accumulation of phosphorus were retarded
(Table V). Increase in level of phosphorus in the nutrient
culture did not help to completely overcome the inhibition
induced by maleic hydrazide. This indicates that the roots
are unable to take up phosphorus as efficiently as the non-
treated plants from the media. Uptake of phosphorus depends
upon an 'active uptake' mechanism involving the use of
respiratory energy (32, 41). A few workers have suggested
that the inhibitory effects of maleic hydrazide on plant
respiration are reflected by the reduced uptake of water
and phosphorus (55, 65).

Foliar applications of maleic hydrazide resulted in
a reduction of respiration of the roots (Table VI). Naylor
and Davis (45, 46), by treating excised roots of several
species of plants with maleic hydrazide came to similar
conclusions. The inhibition of respiration in higher
plants is frequently accompanied by cessation of growth or
undesirable morphological changes (31). Hence the inhibi-
tion of growth in the tomato plants treated with maleic
hydrazide observed, could be attributable to its effect

on root respiration.

-51..

Maleic hydrazide accumulates in actively growing
meristem, affecting cell division and growth (8, 18, 67).
In the shoots of a young tomato plant, the most active
meristem is the apical meristem. 0n the other hand in
roots for every root tip we have an active root meristem
and roots being more in number it can be expected that the
chemical exerts a greater influence on the roots than on
any other organ.

The physiological changes observed in tomatoes
following foliar applications of maleic hydrazide appears
to be mainly due to its effect on the root growth, root

hairs, root tips, root meristems and roots in general.

SUMMARY

Greenhouse experiments were carried out from the fall

of 1958 to the spring of 1960, to study some of the physio-

logical responses of tomato following foliar applications

of maleic hydrazide. Fruit-set in tomato under high night

temperature, as influenced by such applicatiens was of par»

ticular interest. Other responses investigated were,gemnal

growth responses, accumulation of certain nutrient elements,

and respiration of roots in maleic hydrazide treated plants.-

The following were the noteworthy results recorded:

1.

3.

Tomatoes (John Baer) grown under high night
temperature (700 - 80°F), produced few
flowers, a high flower abscission and a
poor fruit-set.

Foliar applications of maleic hydrazide

(20 p.p.m.) followed by growth regulator
treatment (50 p.p.m., BNOA) to fully Opened
flowers increased fruit-set significantly.
It has been indicated that under high night
temperature, failure of pollination is a
secondary factor in influencing fruit-set
in the tomato.

The increased fruit-set recorded in tomato

- 52 -

5.

- 53 -

under high night temperature, was mainly
attributed to foliar applications of maleic
hydrazide. It appears that maleic hydrazide
counteracts the unfavorable influence of
high temperature on plants.

Foliar applications of solutions of 1000
p.p.m. of maleic hydrazide to young tomato
seedlings resulted in the inhibition of their
vegetative and reproductive growth. The

most notable effects were retardations of
stem and root elongation, increase in stem
diameter,. lesser number of leaves per plant
and decreased length of leaves. Alteration
in color, texture and venation of leaves

were also noted.

Maleic hydrazide treated plants tend to
accumulate lesser amounts of some important
nutrient elements such as nitrogen, potassium,
phosphorus, clacium, magnesium, boron, copper
and maganese.

The rate and total accumulation of phosphorus
were retarded, when tomatoes were grown in a
nutrient culture with varying levels of phos-
phorus and treated with maleic hydrazide.

The inhibition induced by maleic hydrazide
could not be overcome effectively by in-

creasing the level of phosphorus in the

-54-

nutrient culture. Roots of the treated
plants were unable to absorb phosphorus
efficiently from the media.
Folhn~applications of maleic hydrazide to
young tomato seedlings influenced the root-
tips, root hairs, and respiration of roots.
Many root-tips showed injury as well as
necrosis. Root hairs were few and appeared
at the very tip of the root. Root elonga-
tion and respiration of roots were also in-
hibited.

It is believed that maleic hydrazide alters
the physiology of tomato plants and induces
inhibition of growth by affecting the root-
tips, root hairs, roots and respiration of

the roots.

7.

10.

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- 58 -

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APPENDIX

-61..

-62-

Table 1: Influence of High Night Temperature (700-800?)

on the Number of Flowers Produced per Cluster

in Tomato (John Baer):

 

Experiment Season Number of Number of Averagehluster

 

Number plants flowers

1. Winter 118 401 3.4
. 1958-59

2. Spring 48 173 3.6

1959

 

-53-

Table 2: Influence of Varying Concentrations of Maleic
Hydrazide on Dry Weights of Shoots and Roots
of Tomato (John Baer). Maleic Hydrazide Applied
as a Foliar Spray to 47 Day Old Seedlings, and
Weights Determined One Month After Application:

 

 

Treatment Average dry Average*dry
weight of weight of
shoots (in gms). roots (in gms).
Control 4.08 1.55
MH - 10 pepeme 3050 1030
MH "’ 100 pepeme 3.30 1005
MH " 1000 pepeme 3013 0.95

v—

 

*A11 weights from an average of six replicates for each
treatment.

MH - Maleic hydrazide.

-54-

 

 

 

Table 3: Effect of Foliar Applications of Maleic Hydra-
zide on the Dry Weights of Tomato (Michigan Ohio
Hybrid) Grown in a Nutrient Culture With Varying
Levels of Phosphorus. Maleic Hydrazide was
Applied to 30 Day Old Seedlings and Weights
Recorded at the Time of Treatment and 28 Days
Following Treatment:
Level of Dry Weights*
Date Phosphorus (in Eng)
(p.p.m.)
December **
6th, 1959 128 0.49
64 0.50
32 0.46
16 0.40
__ Shoots Roots
Control Treated Control Treated
January
3rd, 1960 128 4.00 3.20 1.00 0.60
64 4.60 3.60 .80 0.40
32 3.80 3.40 0.80 0.40
16 3.00 3.00 0.60 0.30

 

**Weights on the whole plant basis for plants removed on
December 6th.

*All weights are averages from three replicates, each
replicate consisting of two plants.

-55-

 

 

 

* .
Initial phosphorus content determined on
for plants removed on December 6th, 1959.

Table 4: Effect of Foliar Applications of Maleic Hydra-
zide on the Phosphorus Contents of Tomato
(Michigan Ohio Hybrid) Grown in a Nutrient
Culture With Varying Levels of Phosphorus.
Maleic Hydrazide Was Applied to 30 Day Old Seed-
lings and Phosphorus Content Determined at the
Time of Treatment, and 28 Days Following Treat-
ment:
Date Level of Concentration
Phosphorus of phosphorus
(p.p.m.) (in percent)
December
6th, 1959 128 1.16
64 1.08
32 . 0.60
16 0.50
Shoots Roots
Control Treated Control Treated
January
3rd, 1960 128 0.80 0.73 1.40 1.44
64 0.61 0.66 0.95 1.20
32 0.51 0.57 0.88 0.77
16 0.47 0.38 0.84 0.60

whole plant basis

-66-

Table 5: Effect of Foliar Applications of Maleic Hydra-
zide on Respiration of Tomato (Michigan Ohio
Hybrid) Root-Tips. Maleic Hydrazide was Applied
at 1000 p.p.m. to 30 Day Old Seedlings, and
Determinations of Rates of Respiration Made
192 Hours After Applications:

Flask ‘ Readings of manometer

Number Initial Final-
4.00 pm. 4.15 4.32 4.50 5.13

 

_——vi

I Control 249 238 238. 238 234
II " 249.5 239 235 234 234
IV Treated 250 248 248 248 248

V " 249.5 247 247 247 247

20 root-tips of 1cm each were used per flask. Final
consumption of oxygen expressed in microliters'on
milligram dry weight of root-tips.

. ARE.
F ‘3‘ ‘g
Luigi's“

329173

K
_r .
g? m