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SUNIVERSITY OF Gulf Coast Research and Education Center
FLO RIDA 5007 60th Street East, Bradenton,FL 34203
Bradenton GCREC Research Report BRA-1993-24
Institute of Food and Agricultural Sciences November 1993
METHODS FOR EXPERIMENTAL PRODUCTION OF EDEMA [
IN SOME CRUCIFERS
"Edema" is the name commonly employed to identify the condition of foliar
intumescence development induced by edema or excess hydration of foliage by
climatic and environmental conditions that cause a low transpiration rate coupled
with high root water pressure (1,3,4,5). These conditions include warm, wet soils
and humid, cool air that retards transpiration. The term edema is defined as the
effluence of serious fluids into the interstices of cells, in tissue spaces, or
into other cavities. The literature indicates that foliar intumescences are most
commonly caused by an edamatous condition. Many plants, however, have edema but
lack development of intumescences (zinnia, and tomato) as may be ascertained
visually by the sub-epidermal water soaked appearance. The list of terms applied
to describe edema (3) is lengthy but conveys a picture of the condition, namely
described as edema, warts, intumescences, galls, plant cancer, tubercles, bulges,
protuberances, swellings, neoplasms, nations, frosty spots, dropsy, and genetic
tumors. Tumor may not be a good term since it is defined as an abnormal swelling
of a circumscribed new growth (overgrowth) of tissue different in structure from
the part in which it grows, and which serves no useful purpose. A' good
description of edemata or intumescences (1) states that they are blister-like,
protuberant, abnormal outgrowths on plants which appear on leaves and
occasionally on stems.
A problem of acute edema of collards in the field came to our attention
(Hillsborough County 1-11-93). Environmental conditions thought to be conducive
to edema were prevalent in that season. The occurrence of this disorder was noted
for reference to methodological studies in foliar physiology. Cabbage varieties
in the field were also observed to have significant cases of foliar intumescence
development in the Winter season 1992-93. Cabbage varieties were selected (2) in
two groups, namely resistant and susceptible for study in the greenhouse as to
the causal factors in foliar intumescence. A single variety of collard was
included in the study.
Materials and Methods
Rationale for Methods. Pressure infusion with water of greenhouse-grown plants
was selected as a method of comparing varieties and eliciting information as to
the etiology of foliar intumescence of crucifers. Penetration of the foliar
epidermis was also accomplished by the use of a wetting agent (Kinetic R)
(polyalkyleneoxide modified polydimethylsiloxane plus nonionic surfactants, 99%
active ingredient, Setre Chem Co., Memphis TN 38137) that contains a silicone
wetting component in the proprietary mixture that lowers surface tension
adequately to permit stomatal penetration by surface-applied liquids. Copper and
sulfite were included in the surface applications to determine whether these
agents would induce plant responses that might be similar to those observed in
the field and suggested as possibly being linked to foliar damage by air
pollutants in combination with residuals from agricultural sprays containing
copper. These suggestions are unpublished (Citrus Leaf and Twig Dieback Task
Force, Florida Department of Environmental Protection). Methods development as
usual was a prelude to the work. Foliar physiology techniques were worked out at
the level of the individual leaf, namely by inducing the crossing of epidermal
barriers by liquids.
The stomatal functioning and aperture situation were evaluated by penetration of
liquids through the stomates into the interstices of the interior as determined
visually after applying drops of penetrant to leaf surfaces. Stomatal liquid
conductance was evaluated by placing drops of a mixture of 60% mineral spirits
and 40% mineral oil on the abaxial surface of freshly detached test leaves. A
time lapse of 10 seconds was allowed for a visible flooding of the sub-epidermal
interstices. Usually this occurred in 1-2 seconds. During cold, low humidity,
and low light conditions, no infiltration occurred in the brief test period.
When stomates were found to be closed, no infiltration was attempted. Whenever
the test indicated stomatal closure existed, pressure infiltration attempts
failed. These methods will be detailed further in later publications.
Single plants of the 10 crucifers employed were grown in triplicate in GCREC
potting media in 15-cm plastic pots. Plants were fertilized with 1 teaspoon of
14-14-14 slow release fertilizer per pot at the soil surface at planting,
repeated at 4 weeks. A commercial micronutrient mix was spread over the soil
surface after planting (one half teaspoon per pot). No pesticides were applied.
Pots were irrigated by hand as required, with attention to the avoidance of
moisture deficiency stress.
Stomatal infusion was accomplished by applying slight pressure to liquid in a
syringe pressed lightly against the abaxial surfaces of the leaves.. Ten ml
syringes were prepared by removing the center plastic barrel with a cork borer,
providing a smooth circular aperture of 7-mm diameter that would infuse a
circular area more or less completely as determined by visual examination. In
some cases the infused area extended past the periphery of a ring made on the
waxy leaf surface by the appressed syringe. Indolebutyric acid or indole acetic
acid were administered similarly as solutions in the syringes in two
observational and one formal experiment. Before infusing the solutions, stomatal
aperture was determined to be adequate by penetration of drops of solutions
applied to the under surfaces of test leaves. Penetration of liquids into the
leaves was clearly visible as a water-soaked appearance over each area of
penetration. Each leaf to be tested received 6 infusions visible as 7-mm diameter
soaked spots. Control treatments involved the same procedure with empty syringes
which produced a marking slightly visible on the leaf when the syringe was
pressed against the leaf and injection of air accomplished. In order to leave
visible marks of air infusion spots, slightly more pressure was used with the dry
syringe, with a slight twisting motion which probably caused more physical injury
to the leaf than occurred with the syringe containing liquid. In a later planting
similar to the first, young plants (5 weeks) were tested for intumescence
production by the water infusion method, comparing cotyledonary and true leaves.
Copper sulfate and sodium bisulfite solutions with Kinetic(R) wetting agent were
brushed onto the abaxial surfaces of the 10 crucifers using a back and forth
brushing motion twice to apply solutions to the lower leaf surfaces at a time
when stomates were open. Solutions were applied using an ordinary nylon bristled
paint brush. The brushing operation redistributed cuticular surface wax to some
Foliar intumescence development followed the various procedures in 3 or more
days. Early signs of development occurred the second day. Swelling of cells and
a rupturing of the epidermis followed effective treatments. In the early stages,
the spots where intumescences were forming developed a lighter green coloration,
possibly due to dilution of chlorophyll. Intumescences were raised above the leaf
surface by 1-2 mm. They were initially green but later developed a corky,
suberized exterior, tan to light brown in color.
Water and air infusion of middle leaves resulted in a wide range of responses
(Table 1). 'Green cup' cultivar cabbage was consistently resistant to
intumescence development. 'Solid Blue 780', 'Solid Blue 790', and 'Tempo'
cultivars were intermediate. The other cultivars reacted with considerable
development of intumescence. Water infusion was significantly more effective in
eliciting response than air infusion. The air infusion procedure is interpreted
as a physical injury procedure and the response likely is due to the injury of
Cotyledonary leaves infused with water were not as consistent in response as the
second true leaves. The second true leaves (counting up from the cotyledons)
appeared to be in good agreement with the field groupings of the cabbage
cultivars. 'Morris Heading' collard cultivar was susceptible to induction of the
Copper and sulfite brushed onto leaves produced considerable development of
intumescence (Table 2). Copper appeared to be the major intumescence-producing
chemical with no added effect from the sulfite. The cabbage cultivars susceptible
to intumescence development in the field also appeared to be more susceptible to
Data in Table 3 show a variable response to 2 levels of indolebutyric acid in
terms of increased intumescence development. Tests are in progress to reduce the
background effect of the method of administering the indolebutyric acid, namely
by spray and other surface application of the compound.
No spontaneous development of intumescences were found in the greenhouse.
Environmental conditions apparently were not favorable to such development under
existing greenhouse conditions. For experimentation, the condition of plant
material and the selection of leaves for treatment should provide succulent test
leaves that are then kept at a higher moisture content during the period awaiting
intumescence development. The cultivars resistant to intumescence development
appeared to have thinner leaves but data were not taken to support this
Methods are given for studying the susceptibility of certain crucifers to
intumescence development. While the disorder does not represent an economic
hazard to cabbage growers, that with collards does represent a condition that may
make a crop unmarketable. Many factors can contribute to the development of
foliar intumescences (commonly termed edema). Accumulation of free water in the
interior of the leaf, physical injury of leaves, and translaminar distribution
of copper seem likely as causal factors.
I. Eisa, H.M., and A.K. Dobrenz. 1971. Morphological and anatomical aspects
of oedema in eggplants. J. Amer. Soc. Hort Sci. 96:766-769.
2. Howe, T.K. and W.E.Waters. 1993. Cabbage cultivar evaluation in west-
central Florida during 1992-93. GCREC Res. Report BRA1993-10.
3. Jaworski, C.A., H.M., Max H. Bass, Sharad C. Phatak, and Anson E.
Thompson. 1988. Differences in leaf intumescences between Cuphea species.
4. Lang, S.P. and T.W. Tibbitts. 1983. Factors controlling intumescence
development on tomato plants. J. Amer. Soc. Hort Sci. 108:93-98.
5. Schoulties and J.J. McRitchie. 1981. Edema. Univ. of Fla. Plant Path.
Circular No. 225, June 1981.
The information contained in this report is a summary of experimental results and
should not be used as recommendations for crop production. Where trade names are
used, no discrimination is intended and no endorsement is implied.
Table 1. Rating indexes (0-10, none to most severe) of foliar intumescences
following water or air infusion of leaves of cabbage and collard.
Water Air Cotyledonary True
Cultivar Infused Infused Mean Leaves Leaves
Cabbage resistant in field
Blue Gem 7.7 7.0 7.3 ab 1.0 bc 4.0 c
Cheers 7.0 3.0 5.0 cd 4.0 b 1.0 d
Green Cup 0.0 0.0 0.0 f 0.0 c 0.0 d
Solid Blue 780 1.3 4.7 3.0 de 3.5 b 2.0 cd
Cabbage intumescent in field
Abbott & Cobb #5 5.0 7.3 6.2 bc 2.5 bc 8.5 ab
Bravo 8.7 3.3 6.0 bc 10.0 a 8.5 ab
Rio Verde 9.3 8.3 8.8 a 2.5 bc 10.0 a
Solid Blue 790 2.3 0.0 1.2 ef 3.0 bc 3.5 c
Tempo 3.7 3.0 3.3 d 2.5 bc 7.0 b
Morris Heading 6.7 2.0 4.3 cd 0.0 c 8.5 ab
Water infused 5.2 a
Air infusted 3.9 b
zControl data all zeros were not included in statistical analysis. ANOVA, LSD
5% level of significance. There was no spontaneous intumescence; infused
areas were identified by circles inscribed on leaves very lightly by
appressing syringe to waxy surface (cuticular wax was disturbed producing
rings). Area including circle and adjacent areas within 3 mm were included
in ratings. Data from cotyledonary and second true leaves were from 5-week
old plants, other data from 8-week old plants.
Table 2. Foliar intumescences ratings 0-10, none to most severe, induced in
cabbage and collard by brushing solutions onto abaxial surfaces of
large leaves in the greenhouse.
Nine-week old plants Five-week old plants
Cultivar H,20z' Cu Cu+S0 Mean H20 Cu SO3 Cu+S03 Mean
Cabbage resistant in field
Blue Gem 0.0 0.8 0.5 0.43b 0.0 1.0 0.0 0.0 0.25c
Cheers 0.0 0.7 0.1 0.27b 0.0 0.5 0.0 0.0 0.13c
Green Cup 0.0 0.3 0.0 O.10b 0.0 0.8 0.0 0.8 0.38c
Solid Blue 780 0.0 0.6 0.0 0.20b 0.0 2.3 0.0 1.0 0.81bc
Cabbage intumescent in field
Abbott & Cobb #5 0.0 10.0 10.0 6.67a 0.5 10.0 0.6 4.5 3.90a
Bravo 0.0 2.0 0.4 0.80b 0.5 1.0 0.5 2.5 1.13bc
Rio Verde 0.1 2.8 1.3 1.40b 0.0 5.0 0.0 3.5 2.13b
Solid Blue 790 0.0 0.2 1.6 0.60b 0.0 1.0 0.0 0.0 0.25c
Tempo 0.0 0.1 0.0 0.03b 0.0 1.0 3.0 0.0 1.00bc
Morris Heading 0.1 0.9 2.1 1.03b 0.0 0.0 6.0 2.5 2.13b
Means 0.02b 1.84a 1.60a O.10b 2.25a 0.71b 1.78a
ZSolutions brushed on leaves were: H,0 = water containing 2 ml KineticR wetting
agent per liter; Cu = 100 pm Cu as CuS04 5 H20 + 2 ml Kinetic/L; SO = 0.005 M
NaHSO3 + 2 ml Kinetic/L; Cu+SO3 = 100 ppm Cu as CuSO4 5 H20 + 2 ml Kinetic/L
0.005 M NaHSO3.
YH20 + Kinetic used as control in ANOVA, LSD 5% level of significance.
Table 3. Foliar intumescence ratings 0-10, none to most severe, resulting from
stomatal infusionz of indolebutyric acid (IBA) and indoleacetic acid
(IAA) in Abbott and Cobb #5 cabbage plants, 6 weeks old.
Days after infusion
Infused chemical 7y 11Y 4X
None, H,0 control 0.08ab 0.67b 0.56c
30 ppm IBA 1.00ab 3.00a 4.00a
100 ppm IBA 3.25a 4.17a 3.50ab
30 ppm IAA 0.08ab 0.60b 1.40bc
100 ppm IAA O.OOb 0.03b 0.50c
200 ppm IAA O.lOab 0.38b 0.60c
z6 spots were infused on 2 leaves each per plant, triplicate plants.
YData from first set of leaves infused. See footnote Table 1.
xData from second set of leaves infused. Plants were sheltered by one layer
of cheesecloth to increase humidity and moderately favor intumescence