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Title: The effect of light on ABA catabolism in excised seedlings of Phaseolus vulgaris L. cv. top-crop

Abstract

Studies on the influence of light quality on ABA catabolism have implicated the involvement of phytochrome in this process. Detailed experiments were therefore carried out to determine whether light could be a factor involved in the regulation of ABA catabolism in higher plants. Excised, etiolated seedlings of Phaseolus vulgaris (4.5g fr. wt.) were supplied with (R,S,)-(2-{sup 14}C)-ABA (5.0 kBq) and exposed to various combinations of red (37 {mu}mol m{sup {minus}2} s{sup {minus}1}) and far-red (23 {mu}mol m{sup {minus}2} s{sup {minus}1}) light. Following light treatments seedlings were returned to darkness for the remainder of the 20 h incubation period. Far-red light illumination stimulated ABA catabolism whereas red light had no significant effect on this process. Kinetic studies and analysis of water-soluble conjugates revealed that far-red light treatment enhanced the sequestration of ABA and its acidic products. The apparent inhibition of ABA catabolism by red light was relieved, if red light irradiation was followed immediately by a dose of far-red light. Thus, these data indicate that ABA catabolism might be mediated by phytochrome and that control is exerted at the level of conjugation rather than oxidation.

Authors:
;  [1]
  1. (Rhodes Univ., Grahamstown (South Africa))
Publication Date:
OSTI Identifier:
5769998
Alternate Identifier(s):
OSTI ID: 5769998
Report Number(s):
CONF-9007196--
Journal ID: ISSN 0079-2241; CODEN: PPYSA
Resource Type:
Conference
Resource Relation:
Journal Name: Plant Physiology, Supplement; (USA); Journal Volume: 93:1; Conference: Annual meeting of the American Society of Plant Physiologists, Indianapolis, IN (USA), 29 Jul - 2 Aug 1990
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 54 ENVIRONMENTAL SCIENCES; ABSCISIC ACID; PHASEOLUS; VISIBLE RADIATION; BIOLOGICAL EFFECTS; CARBON 14 COMPOUNDS; TRACER TECHNIQUES; AUXINS; CARBOXYLIC ACIDS; ELECTROMAGNETIC RADIATION; ISOTOPE APPLICATIONS; LABELLED COMPOUNDS; LEGUMINOSAE; MAGNOLIOPHYTA; MAGNOLIOPSIDA; MONOCARBOXYLIC ACIDS; ORGANIC ACIDS; ORGANIC COMPOUNDS; PLANT GROWTH REGULATORS; PLANTS; RADIATIONS 550201* -- Biochemistry-- Tracer Techniques; 540110

Citation Formats

Cowan, A.K., and Myemane, D.M. The effect of light on ABA catabolism in excised seedlings of Phaseolus vulgaris L. cv. top-crop. United States: N. p., 1990. Web.
Cowan, A.K., & Myemane, D.M. The effect of light on ABA catabolism in excised seedlings of Phaseolus vulgaris L. cv. top-crop. United States.
Cowan, A.K., and Myemane, D.M. Tue . "The effect of light on ABA catabolism in excised seedlings of Phaseolus vulgaris L. cv. top-crop". United States. doi:.
@article{osti_5769998,
title = {The effect of light on ABA catabolism in excised seedlings of Phaseolus vulgaris L. cv. top-crop},
author = {Cowan, A.K. and Myemane, D.M.},
abstractNote = {Studies on the influence of light quality on ABA catabolism have implicated the involvement of phytochrome in this process. Detailed experiments were therefore carried out to determine whether light could be a factor involved in the regulation of ABA catabolism in higher plants. Excised, etiolated seedlings of Phaseolus vulgaris (4.5g fr. wt.) were supplied with (R,S,)-(2-{sup 14}C)-ABA (5.0 kBq) and exposed to various combinations of red (37 {mu}mol m{sup {minus}2} s{sup {minus}1}) and far-red (23 {mu}mol m{sup {minus}2} s{sup {minus}1}) light. Following light treatments seedlings were returned to darkness for the remainder of the 20 h incubation period. Far-red light illumination stimulated ABA catabolism whereas red light had no significant effect on this process. Kinetic studies and analysis of water-soluble conjugates revealed that far-red light treatment enhanced the sequestration of ABA and its acidic products. The apparent inhibition of ABA catabolism by red light was relieved, if red light irradiation was followed immediately by a dose of far-red light. Thus, these data indicate that ABA catabolism might be mediated by phytochrome and that control is exerted at the level of conjugation rather than oxidation.},
doi = {},
journal = {Plant Physiology, Supplement; (USA)},
number = ,
volume = 93:1,
place = {United States},
year = {Tue May 01 00:00:00 EDT 1990},
month = {Tue May 01 00:00:00 EDT 1990}
}

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  • The effect of carbon monoxide and light on the respiration of a number of plant tissues were examined. The respiration of root or other tissue was measured at 25/sup 0/C by standard manometric techniques in a ratio of 95% CO and 5% O/sub 2/. The respiration of all eleven tissues studied was strongly inhibited by carbon monoxide. In ten of the eleven cases examined the inhibition was largely or completely eliminated by irradiation of the tissue with light. The evidence fairly well precludes the participation of a tyrosinase and definitely supports the participation of a cytochrome oxidase in respiration. 5more » references, 1 table.« less
  • Excised light-grown leaves and etiolated leaves of Hordeum vulgare L. cv Dyan catabolized applied (+/-)-(2-/sup 14/C)abscisic acid ((+/-)-(2-/sup 14/C)ABA) to phaseic acid (PA), dihydrophaseic acid (DPA), and 2'-hydroxymethyl ABA (2'-HMABA). Identification of these catabolites was made by microchemical methods and by combined capillary gas chromatography-mass spectrometry (GC-MS) following high dose feeds of nonlabeled substrate to leaves. Circular dichroism analysis revealed that 2'-HMABA was derived from the (-) enantiomer of ABA. Refeeding studies were used to confirm the catabolic route. The methyl ester of (+/-)-(2/sup 14/C)-ABA was hydrolyzed efficiently by light-grown leaves of H. vulgare. Leaf age played a significant rolemore » in (+/-)-ABA catabolism, with younger leaves being less able than their older counterparts to catabolize this compound. The catabolism of (+/-)-ABA was inhibited markedly in water-stressed Hordeum leaves which was characterized by a decreased incorporation of label into 2'-HMABA, DPA, and conjugates. The specific, mixed function oxidase inhibitor, ancymidol, did not inhibit, dramatically (+/-)-ABA catabolism in light-grown leaves of Hordeum whereas the 80s ribosome, translational inhibitor, cycloheximide, inhibited this process markedly. The 70s ribosome translational inhibitors, lincomycin and chloramphenicol, were less effective than cycloheximide in inhibiting (+/-)-ABA catabolism, implying that cytoplasmic protein synthesis is necessary for the catabolism of (+/-)-ABA in Hordeum leaves whereas chloroplast protein synthesis plays only a minor role. This further suggests that the enzymes involved in (+/-)-ABA catabolism in this plant are cytoplasmically synthesized and are turned-over rapidly, although the enzyme responsible for glycosylating (+/-)-ABA itself appeared to be stable.« less
  • Drought tolerance mechanisms in Phaseolus vulgaris (Pv) are still largely unknown. Gas exchange responses and ABA accumulation were monitored in Pv genotypes differing in their drought adaptation. Higher rates of photosynthesis were observed under well-watered conditions in drought sensitive genotypes. Water stress caused a significant reduction in leaf water potential and photosynthetic rates regardless of drought adaptation. Higher photosynthetic rates were maintained under stress conditions in one drought tolerant genotype. Interestingly water stress caused significant ABA accumulation only in this genotype. Root ABA levels were similar among genotypes and were not modified by water stress. Endogenous levels of free ABAmore » in leaves and roots did not correlated with gas exchange response to water stress. These results differ from previous reports on genotypic variation in ABA accumulation under water stress.« less
  • Phaseolus vulgaris L. cv. Provider seedlings were grown in sand culture in a controlled environment chamber. Six-day-old plants were exposed to one of the following dosages of PAN: 1) 271 ..mu..g/m/sup 3/ for 1 hr (subthreshold); 2) 405 ..mu..g/m/sup 3/ for 0.5 hr (subthreshold); 3) 405 ..mu..g/m/sup 3/ 1 hr (above threshold); and 4) 360 ..mu..g/m/sup 3/ for 1 hr (threshold). Exposures were conducted at 75% RH and 25 C beginning at 1100 hours. Stomatal conductance of primary leaves was measured at 1200 hours and 2100 hours on 3 consecutive days beginning one day prior to exposure. No macroscopic symptomsmore » were observed on plants exposed to dosages 1 or 2 and stomatal conductance for these plants remained similar to that of controls. Typical abaxial glazing was observed at dosages 3 and 4 and stomatal conductance for these plants was higher at the 2100 hour reading each night after exposure and lower for the 1200 hour reading one day after exposure. An additional histological study was conducted on primary leaf tissue of plants exposed to dosage 3. Small numbers of abaxial epidermal and spongy mesophyll cells were plasmolized 3 hr after exposure. By 6 and 9 hr after exposure large but similar percentages of epidermal and mesophyll cells were collapsed. Greater numbers of cells adjacent to stomata were injured than at other locations. Guard cells remained intact and normal in appearance.« less