208
FLORIDA STATE
HORTICULTURAL SOCIETY,
3.
Geraldson, C. M.f E. L. Spencer and M. C. Jorgensen. 1954. Chemical analysis as a tool in determining: nutri
tional factors affecting tomato quality.
Proc. Fla. State
Hort. Soc. 57: 123-127.
4.
Geraldson, C. M. 1955. Soil solution soluble salts as
an indicator of fertility level and nutrient balance.
Soil
Sci. Soc. of Fla. Proc. 15: 22-30.
5.
Geraldson, C. M. 1956. Watch nutrient intensity and
balance. Sunshine State Agr. Res. Rep. 1 (3): 10-11.
6.
Geraldson, C. M. 1957. Soil soluble salts—determina
tion of and association with plant growth. Proc. Fla. State
Hort. Soc. 70: 121-126.
7.
Geraldson, C. M. 1957.
Factors affecting calcium
nutrition of celery, tomato, and peppers. Soil Sei. Soc. of
Amer. Proc. 21: 621-625.
8.
Geraldson, C. M. 1963. Quantity and balance of
nutrients required for best yields and quality of tomatoes.
Proc. Fla. State Hort. Soc. 76: 153-158.
1968
9.
J or gen sen, M. C. 1965. Correlation of tomato yields
with the intensity and balance method of soil tests in the
Ruskin area.
A Progress Report.
Proc. Fla. State Hort.
Soc. 78: 163-170.
10.
Llewellyn, W. R. 1963.
Soil testing in southern
Dade County.
Dade County Extension Publication. (Un
published report).
11.
Montelaro, James, Mason Marvel and F. S. Jamison.
1959. Vegetarian—November.
12. Montelaro, James, James NeSmith and C. M. Ger
aldson. 1964. The "Intensity and Balance" method of soil
testing. (Unpublished mimeo report).
13. Tucker, C. A., II. 1968.
Some considerations for
computerizing the Intensity and Balance program. (Un
published Seminole County Extension Publication—revised
as SemCo. Ext. Series 68-3).
14. Westgate, P. . 1950. Effects of soluble soil salts on
vegetable production at Sanford. Fla. State Hort. Soc. 53:
116-123.
INFLUENCE OF LIGHT INTENSITY AND PHOTOSYNTHATE
EXPORT FROM LEAVES ON PHYSIOLOGICAL
LEAF ROLL OF TOMATOES
S. S. Woltz
University of Florida, IFAS
Gulf Coast Experiment Station
Bradenton
roll toward the top of the plant. Margins of
In mild cases,
leaves roll upward and inward.
leaves become
trough
shaped, while
in severe
cases the leaf may form a tight spindle.
The
severity of leaf roll varies with climatic condi
Abstract
The removal of young vegetative shoots and
fruit hands from 'Floradel' tomato plants caused
a rapid and severe increase in physiological leaf
roll.
The disorder began at the bottom of the
plants and progressed upward.
del1 plants with saran screen
Shading 'Flora(25, 50 and 75%
shade) decreased the incidence and severity of
leaf roll which was largely prevented by 50 and
75% shade. Sugar and starch were determined
in the lower leaves and were found to be gen
erally correlated with the degree of leaf rolling.
It is hypothesized that starch accumulation in
lower leaves may be the basic cause of physio
logical leaf roll.
Potential causes of starch ac-
mulation are listed.
Introduction
Tomato plants growing under normal culture
frequently have a characteristic leaf roll varying
from mild to severe. Lower leaves are first to
roll, followed by a gradual development of leaf
Florida Agricultural Experiment Stations Journal Series
No.
3157.
tions, cultural practices and varieties. When
leaf roll is severe, fruits are exposed to full
sunlight which may result in the development of
disorders such as sun scald. An excessive tend
ency toward the disorder may result in the dis
carding of a breeding line or in the lack of ac
ceptance of a tomato variety in the areas where
leaf roll is severe.
There are reports in the literature relative
to the virus-caused leaf roll of potato (1,2,6,9,10)
which indicate that the basic cause of the roll
ing which is similar in appearance to that in
tomato, is basically due to a failure to export
photosynthate followed by deposition of excess
starch and morphological changes resulting in
the characteristic leaf roll. Bremer (4) has de
scribed several types of tomato leaf roll, some of
which are reversible. Nutritional relationships
have been implicated (7,8) in potato and tomato
leaf roll wherein the leaf roll is accentuated by
conditions favoring nitrogen uptake in the form
of the ammonium ion and conversely decreased
when the nitrate ion constitutes a significant
portion
of
the
nitrogen
supply.
Preliminary
studies (11) in Florida indicated that high light
intensity, heavy pruning and poor fruit set or
WOLTZ:
209
LIGHT INTENSITY— TOMATO LEAF-ROLL
fruit removal promoted the appearance of a leaf
roll. Since the leaf roll was non-pathogenic in
nature and appeared to be associated with starch
accumulation as in the case of potato leaf roll
(virus induced), this particular type of roll was
termed physiological leaf roll. It was considered
likely by Gussow (5)
that the common tomato
leaf roll is non-pathogenic and that "pruning
and stopping back" reduce development of the
plant, retarding food export from the leaves
which, in turn, causes the non-parasitic rolling.
Gussow's conclusion was based on observations
ing two spring and two fall seasons.
Since the
response to shade effects was similar in all ex
periments in regard to the major effects of leaf
roll and starch content, the data presented in
this paper are those for 'Floradel' in a spring
planting.
Determinations
respiration
rate
of
and
photosynthetic
chlorophyll
capacity,
content were
carried out as previously described (12). Sugars
were determined by paper chromatography pro
cedures using p-anisidine to develop color after
chromatographing unidimensionally in butanol-
of increased rolling associated with heavy prun
acetic acid-water solvent. Starch was determined
ing.
with Anthrone reagent following acid hydrolysis.
The effect of light intensity on the relative
growth rate of tomato has been determined quan
titatively (3). It was found that the growth
rate, in terms of gain in dry weight increased
steadily as light intensity was increased from 0.1
to full daylight. As full daylight intensity was
approached, however, there was a definite tap
ering off of the response to additional light. The
assimilation rate per unit leaf area was linearly
related to the logarithm of light intensity. Rela
tive growth rate in terms of dry weight increase
for young tomato plants was curvilinearly re
lated to the logarithm of light intensity. The
growth response to increasing light increments
was greatest at low light intensity, tapering off
to very little response to increments as full day
light intensity was approached.
The present report presents results of studies
carried out to identify some of the causes of
physiological leaf roll of tomato and to construct
a theory as to the basic cause.
experiments
were
The removal of various amounts of the young
vegetative shoots and/or fruit hands caused the
lower leaves of tomato plants to develop physio
logical leaf roll.
The speed of development, se
verity and the number of leaves affected were di
rectly related to the degree to which the plant
was deprived of young, developing organs cap
able of utilizing phytosynthate.
Leaf roll began
with lower leaves and, in cases of complete re
moval
of young vegetative shoots and fruit
hands, progressed upward to the top of the
plant, affecting even the smaller leaves which
are not normally affected in the field.
The general effects on the lower leaves of
various degrees of shading are shown in Table
1. As the degree of shading was increased,
leaves developed greater area per leaf, but less
dry weight per unit area and per leaf. Chloro
phyll content and photosynthetic capacity in
creased as the degree of shading was increased.
Respiration rate increased slightly and then de
Methods and Materials
Preliminary
Results
conducted to
creased with increasing shade.
determine the effect on tomato fruit quality of
variations in the quantity of metabolites reach
ing the fruit. The treatments included removal
Leaf roll incidence decreased with increasing
shade (Table 2). Sugars and starch increased
of varying portions (Vs, % and all) of the fruit
cate plots by means of saran shading material
light) but further increases in shade percent
ages to 50 and 75 resulted in sugar and starch
levels that were less than those found at 0 and
25%.
Plant growth and net photosynthesis
seemed to be benefited by 25% shade compared
with full sunlight. The degree of leaf roll ap
pears to be more closely correlated with starch
of three degrees of light interception, namely
than
hands,
shoots.
mature
leaves
and
young
vegetative
The observations to be made later will
deal with the effects of certain of these proce
dures on the incidence and severity of leaf roll.
Artificial shading was undertaken in dupli
25, 50 and 75 per cent shading.
were used as controls.
Unshaded plots
Plots were 15' by 24' in
size to accomodate three rows of tomato plants.
Several varieties of tomato were grown dur
due to 25% shade compared with 0% (full sun
sugar content.
The margins of the lower leaves of heavily
shaded plants (50 and 75% shade) turned down
ward while
the
mid-rib was somewhat raised.
Thus, the shade-grown leaves had a conforma-
210
FLORIDA STATE HORTICULTURAL SOCIETY, 1968
Table 1.
Effects1 of shading on general qualities of tomato leaves2.
Mean
Leaf
Area
Percent
shade
Dry wt/
unit
Area
Dry
wt/
Leaf
Chlorophyll
content/unit
fresh weight
Photosynthetic
capacity/unit
fresh weight
Respiration
rate/unit
fresh weight
0
100
100
100
100
100
100
25
124
82
102
129
148
113
50
155
58
90
150
144
77
75
193
46
89
157
178
71
*Data are presented as percentages of unshaded controls.
^Leaves were sampled about 8 inches above stem base.
tion somewhat the opposite to that of leaves
grown in high light intensity.
Shade-grown
leaves were of a softer texture and had a darker
green coloration.
It
was
observed
that
as
the
sun
traveled
northward, those plants originally shaded (50
and 75%) but later exposed to direct solar
radiation did develop a severe rolling of the
lower leaves.
Discussion
There is considerable circumstantial evidence
to support an hypothesis to the effect that physi
ological leaf roll may be caused by an accumu
lation of starch which results in the character
istic morphological change and leaf-thickening.
When the young shoots, flowers and small fruit
are removed, severe leaf roll occurs rapidly. This
Table 2.
Effects1 of shading on incidence of physiological leaf roll
Percent
Incidence of
leaf roll
shade
and foliar sugar and starch contents.
Fructose
Sugar Contents
Glucose
Sucrose
Starch
Total
content
0
100
100
100
100
100
100
25
78
121
102
146
123
115
50
25
89
92
79
87
66
75
3
86
57
92
78
14
Data are presented as percentage of unshaded controls.
sampled about 8 inches above stem base.
Leaves are
WOLTZ:
LIGHT INTENSITY — TOMATO LEAF-ROLL
procedure would be expected to cause an inter
ruption in. photosynthate export and an accumu
It should
be
pointed
211
out that the shading
procedure as a method of varying light intensity
lation of starch in the older leaves which ordin
causes other variations, namely in the soil and
arily export much of the manufactured photo
micro-climate of the plant. These variations are
synthate.
Data on starch content were not col
lected, however, to support or refute this as
sumption
Heavy
shading
(50
and
75%)
de
doubtless of considerable significance. As exam
ples, soil temperature at a depth of three inches
decreased
by
2°
F
increments
going in order
creased leaf roll, and starch and sugar content.
from
As noted previously (11), the southern side of
winter grown tomato plants had leaf roll while
somewhat, also, even though efforts were made
the northern side did not.
to the
of starch
on
the
side exposed to solar radiation, with supposedly
to
75%
shade.
Soil
moisture
varied
by hand-watering to maintain uniformity.
This was attributed
greater accumulation
0
The leaf roll commonly seen in the field can
be
attributed
partly
to
the
practice of heavy pruning.
common
cultural
The tomato plant is
enhanced photosynthetic activity. When shaded
basically
leaves were later exposed to full sunlight, they
amounts of foliage and fruit than is found with
quickly developed the characteristic physiological
pruned
leaf roll.
has
Many factors could
and
been
of
staked
producing
plants.
recognized
as
much
Excessive
a
cause
of
greater
pruning
leaf
roll.
the hypothesized
Many tomato varieties have been observed by to
starch accumulation and attendant leaf roll. The
pseudo curly top virus causes severe leaf roll in
mato breeders* to have severe leaf roll in Flor
tomatoes.
cause
capable
This disease may interfere with pro
tein synthesis, as frequently occurs with viruses,
ida but not in areas of reduced light intensity.
♦Personal communication
Exp. Stas., July 15, 1966.
thus causing an accumulation of photosynthate
LITERATURE
ordinarily used as an energy and carbon source
for protein synthesis.
Volk
(7 and 8)
availability
indicated that the adequate
of nitrate
nitrogen
reduced nutri
tional leaf roll in potato and tomato. This type
leaf roll could be similar to the type under dis
cussion in the present report. Nitrate nitrogen
is more rapidly taken up than is the ammoniacal
form which could result in a greater utilization
of photosynthate in protein synthesis. Further,
greater
amounts
of photosynthate would theo
retically be used in protein synthesis from ni
trate
than ammonia nitrogen. The conversion
of nitrate to amino nitrogen requires energy
expenditure via the action of nitrate reductase
and other enzymes. Ammonia nitrogen does not
require as much energy expenditure.
By the hypothesis under consideration, any
factor that prevents photosynthate export, such
as an inability to form the common transport
form, sucrose, would result in starch accumula
tion and leaf roll. Conversely, any factor that
lowers the rate of photosynthetic activity such
as low light intensity, or certain nutritional de
ficiencies would result in a lower degree of leaf
roll.
Varieties of high photosynthetic capacity
or poor photosynthate
transport
be much more subject to leaf roll.
ability
would
from J.
M. Walter, Fla. Agr.
CITED
1.
Barton, Wright E. and A. McBain. 1933. Studies in
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2.
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1933.
Studies
in
the
physiology
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5.
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Volk,
G.
M.
and
N.
Gammon,
Jr.
1952.
Effect of
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Bui.
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15
pp.
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9.
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10.
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1..
Woltz, S. S. 1967.
High intensity sunlight may
cause leaf roll and some fruit disorders of tomatoes. Sun
shine State Research Report 12: 10-11.
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9-15.