Showing papers on "Abscisic acid published in 1974"
467 citations
TL;DR: The sooner the ABA is added along the time course of growth, the more effectively it ensures a normal type of embryo development, and the possibility that inhibitors may play a role in zygotic embryo formation is discussed.
Abstract: Cell cultures of caraway (Carum carvi L) were manipulated to foster the development of somatic embryos. Such populations of embryos typically show a range of forms in addition to regular dicotyledonous embryos: multiple or dactyloid embryos, and embryos with accessory structures, fused cotyledons, or mature leaves in lieu of cotyledons. Abscisic acid (ABA), added in concentrations which permit embryo growth and development to occur, has the effect of suppressing many of these abnormalities. Growth in a medium with 10-7 M abscisic acid, especially in the dark, produces "clean" embryos, that is, single structures with excellent cotyledons, unexpanded radicles, and axes free of any proliferations. The sooner the ABA is added along the time course of growth, the more effectively it ensures a normal type of embryo development. Indeed, the resultant somatic embryos closely resemble their zygotic counterparts The significance of these observations in terms of our knowledge of ABA and the possibility that inhibit...
154 citations
TL;DR: The hypothesis that a small change in water potential could affect stomatal resistance to water loss by means of a very sensitive chemical feedback control mechanism is supported.
Abstract: A relationship between abscisic acid concentration and leaf water status is reported. Water potentials were measured in leaves of Ambrosia artemisiifolia L. and Ambrosia trifida L. throughout a period of dehydration of intact plants. Tissues from the same leaves were analyzed for abscisic acid. For both species, abscisic acid began to increase in a critical water potential range (-10 to -12 atmospheres). These data suggest a threshold water potential that stimulates abscisic acid synthesis. The data support the hypothesis that a small change in water potential could affect stomatal resistance to water loss by means of a very sensitive chemical feedback control mechanism.
124 citations
TL;DR: It is proposed that changes in endogenous levels of ABA, and possibly PA, constitute a mechanism for regulating gas exchange in these perennial plants.
Abstract: Both environmental factors and manipulative treatments (such as fruit excision or stem cincturing) were found to alter gaseous diffusion resistances in grape vine foliage. These responses have been analysed in terms of the hormonal physiology of Vitis vinifera L. leaf tissue. Environmental factors such as moisture stress or photoperiod alterations which contributed towards an increase in stomatal resistance (rs) were correlated with increased levels of endogenous abscisic acid (ABA) and phaseic acid (PA) in mature foliage. Conversely, treatments which elicited a decrease in rs were associated with lower levels of both ABA and PA. For example, rs had increased from 1.41 to 7.14 s cm-1 7 days after fruit removal and stem cincturing, while ABA and PA levels rose by 50 and 370 % respectively. This increase in endogenous ABA was not a consequence of decreased leaf water potential; moisture status was actually improved after treatment. It is proposed that changes in endogenous levels of ABA, and possibly PA, constitute a mechanism for regulating gas exchange in these perennial plants.
113 citations
TL;DR: In addition to the previously identified GA20 and GA29 in immature seeds of Pisum sativum L. cv, Progress No. 9, GA9, GA17, GA38, GA44, abscisic acid and dihydrophaseic acid have been identified.
Abstract: In addition to the previously identified GA20 and GA29 in immature seeds of Pisum sativum L. cv. Progress No. 9, GA9, GA17, GA38, GA44, abscisic acid and dihydrophaseic acid have been identified. The levels of GA9, GA17, GA20 and GA29 have been determined throughout seed maturation by GC-MS. GA20 and GA29 are the major gibberellins in terms of quantity, the other gibberellins remain at very low levels throughout development of the seed.
99 citations
TL;DR: The role of various growth-regulating substances in tuberization in Solarium andigena was studied by application of exogenous growth regulators, and by studying variation in the levels of endogenous hormones under tuber-inducing and non-inducing conditions.
Abstract: Summary
The role of various growth-regulating substances in tuberization in Solarium andigena was studied (1) by application of exogenous growth regulators, and (2) by studying variation in the levels of endogenous hormones under tuber-inducing and non-inducing conditions In short-day induced cuttings tuberization was inhibited by gibberellic acid; indole acetic acid and kinetin (6-furfuryl amino purine) caused slight stimulation of tuber growth at low concentrations, but inhibited it at higher concentrations Application of (2-chloroethyl) trimethyl-ammonium chloride (CCC) promoted tuberization in plants growing under non-inducing long-day conditions and in buds produced on isolated plugs of tuber tissue The tuber-inducing effects of CCC were not reversed by simultaneous application of GA3 Levels of endogenous gibberellins decreased markedly under short-day conditions, but there was no difference in the levels of endogenous abscisic acid under long and short days The reduced levels of gibberellins were maintained for at least 2 weeks when induced plants were transferred from short-day to long-day conditions Application of CCC under conditions which promoted tuberization caused a reduction in gibberellin levels The role of growth hormones in the regulation of tuberization is discussed
96 citations
TL;DR: Abscisic acid (ABA) is synthesized from labelled mevalonate by a preparation of lysed chloroplasts isolated from ripening avocado fruit by a number of cofactors required.
81 citations
TL;DR: Ultrastructural changes were correlated with leaf water potential, relative water content, and abscisic acid levels in the leaf, and mesophyll cells were more prone to damage than bundle sheath cells at a leafWater potential of -18.5 bars.
Abstract: Ultrastructural changes were correlated with leaf water potential, relative water content, and abscisic acid levels in the leaf. Mesophyll cells were more prone to damage than bundle sheath cells at a leaf water potential of -18.5 bars. Tonoplast breakdown and cell disruption occurred in 25% of the mesophyll cells. On rewatering, these disrupted cells did not recover. In bundle sheath cells, starch, lost at about -13.5 bars leaf water potential, reappeared within 2.5 hours of rewatering.
76 citations
TL;DR: In this article, the xylem of excised maize roots was studied in roots bathed in solutions containing kinetin or abscisic acid (ABA), which reduced the water permeability of the roots whilst ABA increased it.
Abstract: Summary
Exudation from the xylem of excised maize roots was studied in roots bathed in solutions containing kinetin or abscisic acid (ABA). Kinetin reduced the water permeability of the roots whilst ABA increased it. The action of both hormones was reversible and both were effective at concentrations of 10-6M and below. The possible in vivo role of these two hormones is discussed.
73 citations
TL;DR: Although the stratified embryos may have an increased capacity to metabolize abscisic acid, the authors' calculations suggest that such an increase capacity would probably not be physiologically significant.
Abstract: Embryos from dormant and stratified Fraxinus americana seed were incubated with (S)-2-(14)C-abscisic acid (ABA) under a variety of conditions. Both dormant and stratified embryos rapidly metabolize abscisic acid to phaseic acid, dihydrophaseic acid, and an unidentified polar metabolite apparently derived from dihydrophaseic acid. Although the stratified embryos may have an increased capacity to metabolize abscisic acid, our calculations suggest that such an increased capacity would probably not be physiologically significant.Dormant intact seeds also metabolize (S)-2-(14)C-abscisic acid during stratification at 5 C or incubation at 25 C. The metabolites appear to be similar to those observed in excised embryos although by 12 days of stratification a fourth metabolite is observed. More than 90% of the (14)C-abscisic acid was metabolized after 26 days of stratification at 5 C or after 12 days of incubation at 25 C. Stratification at 5 C leads to the breaking of dormancy while incubation at 25 C does not.
73 citations
TL;DR: In this paper, the effects of fusicoccin on the germination of dormant, light-requiring or abscisic acid-inhibited seeds has been investigated.
Abstract: The effects of fusicoccin on the germination of dormant, light-requiring or abscisic acid-inhibited seeds has been investigated.
(1) Fusicoccin (10−6M) induces germination in dormant wheat seeds (Triticum durum cv. Cappelli; 1972 crop) and stimulates it in seeds already relieved from dormancy (1971 crop), with an effect similar to that of gibberellic acid.
(2) Fusicoccin (1.5 × 10−6M) is more active than the two phytohormones gibberellic acid and benzyladenine and than white light in stimulating light-requiring lettuce seeds (Lactuca sativa cv. Grand Rapids) to germinate. Germination of radish seeds (Raphanus sativus) is also accelerated by fusicoccin, while benzyladenine and gibberellic acid are less active in this material.
(3) Fusicoccin (1.5 × 10−5M) removes almost completely the inhibitory effect of abscisic acid on germination of radish and lettuce seeds, whereas benzyladenine (10−4M) and gibberellic acid (3 × 10−4M) remove the inhibition only partially.
The possible relationship between these results and previous information on growth by cell enlargement is discussed in terms of the mechanism of action of fusicoccin as compared with natural hormones.
TL;DR: The influence of several natural and synthetic hormones on apical dominance of pea roots was investigated, and cytokinins investigated (kinetin, benzyladenine, and zeatin) showed a strong influence.
Abstract: The influence of several natural and synthetic hormones on apical dominance of pea roots was investigated. Extracts of roots decapitated just before extraction or 12 h earlier were compared in a lateral root formation assay, in the Amaranthus assay for cytokinins and the Avena coleoptile assay. Indole-3-acetic acid shows a strong promotive effect on the initiation of lateral roots. Gibberellic acid has no significant effect. Abscisic acid and its presumable precursor xanthoxin show a strong inhibitory effect, and so do all cytokinins investigated (kinetin, benzyladenine, and zeatin). Decapitation of roots caused a significant increase in the number of lateral root primordia within 12 h. Paper chromatograms of root extracts indicate the presence of at least two inhibitors of lateral root formation in the alkaline fraction, and of two promoters in the acid fraction. The amount of both inhibitors seems to decrease if the tip of the main root is removed 12 h before extraction whereas the promoters of lateral root formation do not change in their concentration. The Amaranthus test shows cytokinin activity in the region of one of the two inhibitors, and this activity decreases after decapitation. The second inhibitor has the Rf of xanthoxin; it inhibits the growth of Avena coleoptiles and its activity also decreases after decapitation.
TL;DR: It is likely that ABA may be involved, to some extent, in the mechanism conferring tolerance of plants to drought.
Abstract: THE level of growth inhibitor in plants increases when they are subjected to water stress and the major constituent of this inhibitor is abscisic acid (ABA)1–3. By its effect in closing stomata, ABA can control the rate of transpiration4–7 and it is therefore likely that ABA may be involved, to some extent, in the mechanism conferring tolerance of plants to drought.
TL;DR: In water-deprived seedlings, abscisic acid increased the total dry matter, reflecting improved efficiency in water-use and, in addition, the growth period and survival of water- Deprivation seedlings were markedly prolonged.
Abstract: The effect of abscisic acid on plant growth and survival during water deprivation was studied in barley and wheat seedlings. Under conditions of both limited and ample water supply, treatment with abscisic acid greatly reduced transpiration and, in addition, suppressed root growth. In water-deprived seedlings, abscisic acid increased the total dry matter, reflecting improved efficiency in water-use. In addition, the growth period and survival of water-deprived seedlings were markedly prolonged. In field trials, however, abscisic acid had no significant effect on waterdeprived seedlings. Possible reasons for this lack of response are discussed.
TL;DR: In this article, the effects of NaCl and abscisic acid (ABA) on protein synthesis, protein hydrolysis, glutamine synthetase, Δ-pyrroline-5-carboxylate reductase and amino acid composition have been studied in aerial parts of Pennisetum typhoides (Stapf et Hubbard) seedlings.
Abstract: The effects of sodium chloride (NaCl) and abscisic acid (ABA) on protein synthesis, protein hydrolysis, glutamine synthetase, Δ-pyrroline-5-carboxylate reductase and amino acid composition have been studied in aerial parts of Pennisetum typhoides (Stapf et Hubbard) seedlings Whereas protein synthesis is inhibited by NaCl and ABA, the activity or the synthesis of leucine-arylamidase, glutamine synthetase and Δ-pyrroline-5-carboxylate reductase is promoted by both the substances The results of the amino acid analysis showed that in the presence of NaCl and ABA the amounts of alanine, aspartate and ammonia decreased, while the concentrations of glutamate, and especially that of proline increased greatly The possible significance of the results in explaining the proline accumulation under stress conditions and ABA-treatment is discussed
TL;DR: There is no correlation between xanthoxin and (+)-abscisic acid levels in spinach on the one hand, and growth and flowering responses on the other.
Abstract: The levels of the growth inhibitors(+)-abscisic acid and xanthoxin were determined in the long day plant spinach (Spinacia oleracea L. cv. Savoy Hybrid 612) grown under different environmental conditions. When plants were transferred from light to darkness, the (+)-abscisic acid level always decreased, whereas the xanthoxin content did not change. The (+)-abscisic acid content was higher in plants grown under low than under high relative humidity.Xanthoxin levels were not affected by photoperiod, whereas the (+)-abscisic acid content increased 2 to 3 times upon transferring plants from short day to long day. Shoot tips with young leaves and mature leaves of the same plants analyzed separately did not differ in their inhibitor content when expressed per unit dry weight. No increase in xanthoxin level was observed in wilting plants. In general, the xanthoxin levels of spinach were much less affected by changes in the environment than were those of (+)-abscisic acid. In conclusion, there is no correlation between xanthoxin and (+)-abscisic acid levels in spinach on the one hand, and growth and flowering responses on the other.
TL;DR: It is suggested that both IAA and acid inhibitors may play an important role in the control of stem growth and differentiation, although light effects on other hormones and regulatory systems cannot be ignored.
Abstract: Indol-3yl-acetic acid (IAA) was identified in Phaseolus vulgaris L. Shoot tissue of seedlings, exposed to light for 5 days, had a higher level of IAA than etiolated seedlings of the same age. The content of IAA increased in green seedlings during light treatment for 5–12 days. No increase could be measured in dark-grown seedlings. Inhibitory substances appeared at different Rf-values. The main part was identical to the inhibitor-β complex and occurred in a higher amount in light-grown seedlings than in etiolated taller ones. One part of the inhibitor-complex appeared to be abscisic acid (ABA). It is suggested that both IAA and acid inhibitors may play an important role in the control of stem growth and differentiation, although light effects on other hormones and regulatory systems cannot be ignored.
TL;DR: In combination with salt, however, GA tended to counteract the effect of salt on both growth and enzyme activity, which may explain adaptation of plants under conditions of stress.
Abstract: Seedlings of Pennisetum typhoides were grown in sodium chloride (NaCl) and gibberellic acid (GA3) separately and in combination, and the effects on the activity of amylase, phosphorylase, aldolase, invertase, hexose-phosphateisomerase, sucrose-synthetase and sucrose-6-phosphate-synthetase were studied. Treatment of the seedlings with NaCl caused an inhibition of the activity of amylase and invertase in the leaf homogenate, but enhanced that of phosphorylase, aldolase, sucrose-synthetase and sucrose-6-phosphate-synthetase. GA3 alone, as observed earlier, promoted the activity of invertase but indicated no significant influence on the other enzymes tested. In combination with salt, however, GA3 tended to counteract, partially or wholly, the effect of NaCl on the activity of several enzymes tested. The possible significance of the similarities between the action of abscisic acid (ABA) and salinity in influencing growth and metabolism of plants during stress is discussed.
TL;DR: Sorghum plants that had been subjected to different degrees of water stress were examined for the occurrence of endogenous compounds capable of inducing stomatal closure, i.e. “antitranspirants”.
Abstract: Sorghum plants that had been subjected to different degrees of water stress were examined for the occurrence of endogenous compounds capable of inducing stomatal closure, i.e. “antitranspirants”. Acidic extracts contained increased amounts of abscisic acid (ABA) as the amount of stress increased, but another highly active compound easily distinguished from ABA also accumulated. This compound, also found in neutral extracts, was probably all trans-farnesol, an isoprenoid alcohol which, like ABA, is a sesquiterpenoid. Highly dilute solutions of “commercial” farnesol induced stomatal closure when applied to isolated epidermis of Commelina.
TL;DR: At least two root-growth-inhibiting substances have been detected in extracts of Zea mays root tips and one has chromatographic properties similar to those of abscisic acid (ABA) and is largely confined to the cap.
Abstract: At least two root-growth-inhibiting substances have been detected in extracts of Zea mays root tips. One has chromatographic properties similar to those of abscisic acid (ABA) and is largely confined to the cap. Another, which has not been identified, is present in the root apex but not in the cap. Indole-3yl-acetic acid (IAA) is never detected in the root cap. Xanthoxin may be present in the root tip.
TL;DR: There are unresolved difficulties inherent in the “cytokinin hypothesis” of phytochrome and gibberellin action that lead to increases in active cytokinin levels in seeds.
Abstract: Cytokinins overcome the inhibitory effect of abscisic acid on the germination of isolated embryos of Grand Rapids lettuce. We have used this fact to assess the content of cytokinins in embryos removed from intact seeds which have been supplied with these growth substances i.e. to determine hormonal uptake. The method has also been used to examine the hypothesis that phytochrome and gibberellin lead to increases in active cytokinin levels in seeds. Appreciable amounts of cytokinins enter intact seeds yet seem unable to promote germination. On the other hand, little or no cytokinin-like activity seems to result from light or gibberellin treatments. We conclude that there are unresolved difficulties inherent in the “cytokinin hypothesis” of phytochrome and gibberellin action.
TL;DR: In this article, Abscisic acid was characterized from extracts of isolated pea chloroplasts by combined gas-chromatography-mass spectrometry. But they used a single ion monitoring of the base peak (m/e 190) in the mass spectrum.
Abstract: Abscisic acid was characterized from extracts of isolated pea chloroplasts by combined gas-chromatography-mass spectrometry. By single ion monitoring of the base peak (m/e 190) in the mass spectrum, 8.6 μg ABA were detected in chloroplasts isolated from 1 kg fresh weight of pea shoots.
TL;DR: Uptake of 3,0-methylglucose and proline were inhibited by ABA to a much smaller extent than that of K+, a result which suggests that ABA acts on specific ion uptake mechanisms.
Abstract: The effect of abscisic acid (ABA) on uptake of potassium (86Bb+ or 42K+) by Avena sativa L. coleoptile sections was investigated. ABA lowered the potassium uptake rate within 30 min after its application and inhibition reached a maximum (ca. 75%) after 2 h. The inhibition of K+ uptake increased with ABA concentration over a range of 0.03 to 10 μg/ml ABA. At a higher K+ concentration (20 mM) the percentage inhibition decreased. The percentage inhibition of K+ uptake by ABA remained constant with external K+ varied from 0.04 to 1.0 mM. After a loading period in 20 mM K+ (86Rb+), apparent efflux of potassium was only slightly increased by ABA. Experiments in which growth was greatly reduced by mannitol or by omission of indole-3-acetic acid from the medium indicated there was no simple quantitative correspondence between ABA inhibition of coleoptile elongation and ABA inhibition of K+ uptake. Chloride uptake was also inhibited by ABA but to a smaller degree than was K+ uptake. No specificity for counterions was observed for K+ uptake. Uptake of 3,0-methylglucose and proline were inhibited by ABA to a much smaller extent (14 and 11%) than that of K+, a result which suggests that ABA acts on specific ion uptake mechanisms.
TL;DR: A remarkable synergistic increase in C2H4 production was observed when Ca2+ and kinetin were applied together, but no synergistic effect ofCa2+ was observed with indole-3-acetic acid or GA3.
Abstract: A slight increase in ethylene production resulted from the application of either kinetin or Ca2+ to mungbean (Phaseolus mungo L.) hypocotyl segments, but a remarkable synergistic increase in C2H4 production was observed when they were applied together. The induction time was about 6 h as compared to 1 h for auxin-induced C2H4 production. A slight stimulation of C2H4 production was also observed when Ca2+ was applied with abscisic acid, but no synergistic effect of Ca2+ was observed with indole-3-acetic acid or GA3.
TL;DR: The effect of plant injection with growth regulators on the dormancy of onion bulbs cv.
Abstract: Experiments were conducted to study the effect of plant injection with growth regulators on the dormancy of onion bulbs cv. Elba Globe. Application of abscisic acid induced early senescence of the leaves and prolonged the rest period of the bulbs. This effect was partially overcome by subsequent applications of gibberellin, auxin or cytokinin and totally overcome with the application of a mixture of the three hormones. Maleic hydrazide application prolonged the rest period by inhibiting both sprouting and rooting of the bulbs throughout the storage period. This inhibitory effect was not overcome by the subsequent application of auxin, gibberellin, kinetin, or their combinations. Ethephon application increased rooting of bulbs and partially overcame the effect of abscisic acid on dormancy.
TL;DR: After application of (±)-[2-14C] ABA to wilted pea shoots at the time of watering radioactive substances appear in the water-soluble, ether-insoluble fraction of ethanolic extracts and increase with time whereas radioactivity in the acidic ether fraction decreases.
Abstract: When pea seedlings lose about 5% of their water content the abscisic acid ((+)-ABA) level of the shoots increases ca. 20 times and the level of bound ABA, in all probability ABA-glucose, ca.7-10 times. After watering both ABA and bound ABA contents decrease within 24–48 h to the level in the control plants.