Increase In Abscisic Acid Content Research Articles

The relationship of abscisic acid metabolism to stomatal conductance in Douglas‐fir during water stress

Changes in abscisic acid and its metabolites were followed through two drought cycles in Pseudotsuga menziesii (Mirb.) Franco seedlings to determine the metabolic pathway of the hormone and its relationship to branch (stomatal) conductance. Three year‐old, intact seedlings were water‐stressed, watered, and restressed over a period of 30 days. Water potential was sampled with a pressure chamber and branch conductance with a steady‐state porometer. Needle content of abscisic acid and 2‐trans‐abscisic acid and their saponifiable conjugates were quantified with gas‐liquid chromatography. The typical water potential threshold in branch conductance, decreasing abruptly at ‐2.0 MPa, corresponded to an increase in abscisic acid content of 240 ng g−1. The relationship between abscisic acid and water potential was not definitive, though the general trend was an increase in the hormone with intensifying stress until water potential was ‐5.0 MPa, when concentration sharply declined. No adjustment to stress was observed in the relationships, but stress during the second cycle progressed more slowly. A linear relationship between abscisic acid and its conjugate indicated the importance of the interconversion of the two compounds for storage and supply of the free acid.

Evidence against an intermediary role of abscisic acid in stomatal closure induced by phenylmercuric acetate and faresol

The hypothesis was tested that stomatal closure induced by the antitranspirants phenylmercuric acetate and farnesol is mediated by an increase in abscisic acid content. Isolated leaves of Spinacia oleracea L. cv. Müma, Tradescantia X andersoniana Ludw. et Rohw. and Commelina communis L. were incubated in solutions of phenylmercuric acetate (10−3M) and of farnesol (2 × 10−3M). In all three species, a reduction in stomatal aperture was observed. The extent and velocity of the reaction differed between the species and also between the two compounds applied. The abscisic acid content of the leaves was determined after stomatal closure had been achieved. No significant increase in abscisic acid level was found in treated leaves of Spinacia and Commelina. In Tradescantia, on the contrary, a reduction to about 50% was observed after 120 min treatment. Visible damage of the treated leaves and membrane alterations observable by electron microscopy occurred, especially after treatment with farnesol. These changes in membrane structure suggest a connection with the reduction in stomatal aperture.

Influence of potassium nutrition and water stress on the content of abscisic acid in grains and flag leaves of wheat during grain development

AbstractIncreasing the potassium (K) supply to wheat plants grown in pots extended the period of grain filling and increased the rate of grain growth, thus increasing the single grain weight. In all K treatments abscisic acid (ABA) content in the grain reached a maximum and this occurred when the growth rate of the grain declined and full ripening commenced. Increasing the K supply delayed the occurrence of the ABA maximum and reduced its absolute value. It seems that an extension of the grain filling period by better K nutrition might not only be due to a longer production of assimilates, but also due to a retarded and lower production of ABA in the grain. This result is supported by the finding that withholding of water supply for 1‐week periods during grain development increased ABA content in the grain and reduced single grain weight.

Effects of excess cobalt, nickel and zinc on the water relations of Phaseolus vulgaris

The relationship between the water status of unifoliate leaves and leaf orientation of bean seedlings exposed to excess cobalt, nickel and zinc was examined. Within one day each metal caused the leaves to drop, but changes in leaf angles were not related to losses in relative water contents or water potentials of shoots and leaves. On the contrary, measurements of these parameters were higher in the treated plants than in the controls. Thus, water stress of the whole leaves cannot be invoked to explain the initial loss of leaf orientation that occurred following exposure of the plants to toxic levels of metal ions. While all three metals induced some stomatal closure, treatment with zinc caused the most pronounced effect. Zinc also induced a fivefold increase in abscisic acid content of the leaves, even though the relative water contents and water potentials were the highest of any treatment.

Effect of abscisic acid on maize root growth. A critical examination

The effect of abscisic acid (ABA) on the growth of maize roots maintained in the dark is investigated in relation to the root varieties and the root age, the mode of application, the concentration used and the duration of both the treatment and the culture. In all the assays, when ABA produces a significant change in root elongation, it shows an inhibitory effect which is enhanced with increasing ABA concentration. The data strongly support the hypothesis that ABA could be one of the growth inhibitors which are formed in or released from the root cap.

Abscisic acid levels and stomatal behavior during drought and recovery in Douglas-fir (Pseudotsuga menziesii)

Foliage of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings from xeric and mesic environments was sampled during two induced, consecutive, drought cycles to determine relationships among leaf resistance, plant water potential, and abscisic acid (ABA) concentration. One group of seedlings was placed in a growth room; the other was kept outside at a nursery under natural conditions. During the first drought cycle, seedlings transpired similarly. During the second drought, xeric seedlings in the growth room and nursery initiated stomatal closure at greater levels of plant moisture stress (PMS) than in the first drought cycle, but stomatal behavior of mesic seedlings was unchanged. During the first drought cycle, a sharp increase in ABA concentration in both ecotypes coincided with increased leaf resistance within a narrow water-potential range. However, after xeric seedlings were rewatered and then subjected to drought, leaf resistances remained low even though the previous threshold PMS and ABA concentrations for stomatal closure were reached. For mesic seedlings in the growth room, ABA concentrations remained high after rewatering and slowly decreased with time, although recovery to predrought leaf resistances was largely completed 2 days after rewatering.

Isolation of abscisic acid-resistant variants from tobacco cell cultures

The goal of this work was to begin a genetic study of the molecular mode of action of abscisic acid (ABA), by isolating variant cultured cells resistant to the hormone, or to a factor which induces ABA synthesis, namely water stress. Cell cultures of Nicotiana tabacum L. cv. Wisconsin 38 and N. silvestris Speg. and Comes were chosen as the experimental materials. Studies of the effects of the two stresses on the growth of the cultures demonstrated that ABA or water stress imposed by mannitol could completely inhibit growth. These effects arose in both cases from a constant reduction of the growth rate of the cells throughout the culture period. Mannitol also induced an increase in ABA content of the cells and media of suspension cultures, although not to the concentrations required to achieve the same degree of growth inhibition when the hormone was applied exogenously.

Physiological Studies on Photochemical Oxidants injury in Rice Plants. : I. Varietal difference of abscisic acid content and its relation to the resistance to ozone.

In order to determine the abscisic acid relationships in the resistance of the rice plants to ozone, endogeneous abscisic acid content in varieties with different sensitibity to ozone was examined. 1. The cultivars differed in their visible injury to ozone fumigation. Nipponbare and Jinheung were more sensitive than Tongil, Milyang No. 23 and Te-tep. 2. Endogeneous abscisic acid content in the resistant variety (Tongil) was higher than in the sensitive one (Nipponbare). 3. Visible injury caused by ozone fumigation was decreased by application of abscisic acid. 4. Abscisic acid content in rice cultivars was found to increase differently depending on varieties response to ozone fumigation (0.3 ppm for 3 hours). The increase of abscisic acid content caused by ozone fumigation was higher in Nipponbare than in Tongil, although the endogeneous level of abscisic acid was higher in Tongil than Nipponbare.

Effects of Kinetin on Transpiration Rate and Abscisic Acid Content of Water Stressed Young Wheat Plants

AbstractEffects of kinetin on transpiration rate and abscisic acid content were determined. Leaves from 9‐day‐old wheat plants (Triticum aestivum L. cv. Weibull's Starke II) were used. —Transpiration rate decreased in excised leaves put in water, but it was maintained at a higher rate when kinetin was supplied. When excised leaves were water stressed by air‐drying for 1 h, addition of kinetin resulted in a considerable stimulation of transpiration rate. The effect reached its maximum after 15 h and this level remained relatively unchanged for at least 10 h. Intact seedlings which were stressed before leaf excision, showed only a slight stimulation of kinetin on transpiration rate. — Abscisic acid content slowly increased up to three‐fold in 2 days in excised leaves put in water. In excised and water‐stressed leaves the abscisic acid content was reduced during the first 24 h and then increased. As the leaves were fully turgid, the increase could not have been caused by water stress. However, both in stressed and unstressed leaves kinetin addition reduced the increase in abscisic acid content. — It is suggested that the stimulation by kinetin on transpiration rate in excised and water stressed leaves was mainly due to the combined effect of (1) a reduction in the activity of endogenous cytokinins, (2) kinetin acting as a ‘substitute’ for the inactivated cytokinins but exerting a stronger effect on transpiration than the endogenous cytokinins, and (3) the ‘extra’ reduction in abscisic acid content caused by the kinetin treatment. Furthermore, the results indicate that changes in cytokinins might be partly responsible for the aftereffect on transpiration.

Effect of Pod Removal on Abscisic Acid Levels in Soybean Tissue1

The seasonal profiles of free and conjugated abscisic acid (ABA) in seed, pod wall, and leaf tissue were determined using field‐grown control and depodded ‘Clay’ soybean (Glycine max (L.) Merr.) plants. Total seed ABA was initially high (13.0 /µg/g fresh weight) but decreased to 0.4 µg/g at maturity. The pod wall contained much less ABA than did seeds (ca. 0.5 µg/g). Pod wall ABA level was constant during development except for a twofold increase during final pod maturation. Leaves also contained much less ABA (< 1 µg/g) than did seeds. Upper canopy leaves contained more ABA than did lower canopy leaves. Depodding had no consistent effect on leaf ABA levels. Water stress caused an increase in ABA content in leaf tissue with no effect on pod wall tissue, while senescence increased ABA content hi pod walls with little effect on leaf tissue.

Identification of ABA Stereoisomers in French Prune Seeds and Association of ABA with Ethylene-enhanced Prune Abscission1

Abstract Excised fruiting branches of French prune (Prunus domestica L.) were treated with 15 μl/liter ethylene (ETH), which inhibited fresh weight increase and caused abscission of immature fruit. Inhibition of fresh weight accumulation was much greater 30 days after full bloom than 44 days after full bloom. Abscisic acid (ABA) in fruit pericarp and seed was extracted, purified for determination by gas chromatography, and identified by gas chromatography-mass spectrometry. ETH treatment significantly increased ABA concentration of pericarp and seed. The inhibition of growth by ETH was similar for pericarp and seed while the increase in ABA was much greater in pericarp than in seed. The trans, trans-ABA was detected only in the seed and the cis, trans-ABA: trans, trans-ABA ratio was reduced by ETH.