Showing papers on "Abscisic acid published in 1975"
TL;DR: A new method for abscisic acid extraction and purification was developed to handle large numbers of small samples of leaf discs, andaired stomatal functioning after stress does not appear to be associated with high residual levels of absc isic acid in the leaf.
Abstract: A new method for abscisic acid extraction and purification was developed to handle large numbers of small (about 125 milligrams fresh weight) samples of leaf discs. This method enabled short term changes in abscisic acid to be followed in single leaves.Water potentials, stomatal diffusion resistance, and abscisic acid levels were measured in the leaves of maize (Zea mays L. var. Wisconsin 575) and sorghum (Sorghum bicolor, hybrid NK 145) plants subjected to a drought-recovery cycle under controlled environmental conditions. The levels of abscisic acid began to rise, and the stomata closed, over a narrow range of water potential (-8 to -10 bars) in both species. Abscisic acid levels continued to rise after the stomata closed. The maximum amount of abscisic acid extracted from maize leaves was about twice that from sorghum, but this represented a similar proportional increase over the control level.In excised leaves little or no change in abscisic acid levels was found within 60 to 120 minutes after stress was applied (phase I). Subsequently abscisic acid levels rose rapidly to about 20 times the prestress level (phase II). Stomatal closure always preceded the phase II increase in abscisic acid.The aftereffects of stress differed in the two species. In sorghum control levels of both abscisic acid and stomatal resistance were regained within 24 hours of rewatering. In maize abscisic acid levels also fell rapidly, but regained control levels only after 48 hours. The resumption of normal stomatal functioning occurred after a further 24 hours.Impaired stomatal functioning after stress does not appear to be associated with high residual levels of abscisic acid in the leaf.
207 citations
TL;DR: Marked changes in the germination capacity of the maturing seeds are closely associated with changes in extractable amounts of methyl-4-chloroindol-3yl acetate and abscisic acid, suggesting that high concentrations of these substances in the embryo, rather than any restriction imposed by the testa, may prevent precocious germination of the seeds.
Abstract: Developing fruits of Pisurn sativum, L., cv. 'Alaska', contain relatively large amounts of hor mones, mainly concentrated in the embryos and liquid endosperm. A close relationship can be demonstrated between changes in extractable amounts of gibberellins (mainly GA20), auxins (methyl 4-chloroindol-3yl acetate and probably 4-chloroindol-3yl acetic acid), and abscisic acid, and changes in growth rates of both the pod wall and seeds. Growth of the pod wall appears to depend largely on hormones supplied by the seeds. Marked changes in the germination capacity of the maturing seeds are closely associated with changes in extractable amounts of methyl-4-chloroindol-3yl acetate and abscisic acid. It is believed that high concentrations of these substances in the embryo, rather than any restriction imposed by the testa, may prevent precocious germination of the seeds.
205 citations
TL;DR: It is suggested that stomata close if the cytoplasm of the guard cells contains much malate and H+, which leads to the inference that ABA inhibits the expulsion of H+ from guard cells.
Abstract: Open stomata of detached leaves of Xanthium strumarium L. closed only when carbon dioxide and abscisic acid (ABA) were presented simultaneously. Three parameters of stomatal closing were determined after additions of ABA to the irrigation water of detached leaves, while the leaves were exposed to various CO2 concentrations ([CO2]s) in the air; a) the delay between addition of ABA and a reduction of stomatal conductance by 5%, b) the velocity of stomatal closing, and c) the new conductance. Changes in all three parameters showed that stomatal responses to ABA were enhanced by CO2; this effect followed saturation kinetics. Half saturation occurred at an estimated [CO2] in the stomatal pore of 200 μl l-1. With respect to ABA, stomata responded in normal air with half their maximal amplitude at [ABA]s between 10-6 and 10-5 M(+-)-ABA. The amounts of ABA taken up by the leaves during the delay increased with a power <1 (on the average, 0.67) of the [ABA] in the transpiration stream. The minimal amount of ABA found to produce a stomatal response was about 1 pmol of (+-)-ABA per cm2 leaf area, almost two orders of magnitude smaller than the original content of the leaves in ABA indicating that most of the endogenous ABA was in a compartment isolated from the guard cells. An interaction between stomatal responses to CO2 and ABA was also found in Gossypium hirsutum L. and Commelina communis L.; it was however much weaker than in X. strumarium. Based on earlier findings and on the results of this investigation it is suggested that stomata close if the cytoplasm of the guard cells contains much malate and H+. The acid content in turn is determined by the relative rates of production of malic acid (from endogenous as well as exogenous CO2) and its removal (by transport of the anion into the vacuole and exchange of the H+ for K+ with the environment of the guard cells). The simultaneous requirement of CO2 and ABA for stomatal closure leads to the inference that ABA inhibits the expulsion of H+ from guard cells.
161 citations
TL;DR: Gibberellin A3 (GA3) or abscisic acid (ABA) did not affect the number of embryos formed in the globular and early heart stages but caused a decrease of those in the heart and torpedo stages.
157 citations
TL;DR: It is concluded that pigment breakdown, which is widely used as an index of leaf senescence, may not be an inevitable part of the aging process.
Abstract: Chlorophyll levels in l-cm sections of the youngest fully expanded leaves of normal (Y) Festuca pratensis L. declined almost to zero over a period of 6 days after excision. Chlorophyll in a mutant genotype (NY) remained near the initial level for the whole of this period. Abscisic acid promoted pigment loss in Y but had no significant effect on chlorophyll in NY. Kinetin retarded pigment loss in Y but was ineffective in NY. Other biochemical changes associated with leaf senescence—reduction in protein content and the appearance of novel isoenzymes of α-naphthyl acetate esterases—occurred in both genotypes. Abscisic acid accelerated protein breakdown, whereas kinetin inhibited the loss of protein in both genotypes. The mutation thus appears to be expressed as a highly specific lesion in pigment metabolism. We concluded that pigment breakdown, which is widely used as an index of leaf senescence, may not be an inevitable part of the aging process.
117 citations
TL;DR: Abscisic acid moves basipetally and laterally in maize root segments placed horizontally; its transport properties are thus similar to those of the growth-inhibiting substances produced by the root cap.
Abstract: Abscisic acid (ABA) moves basipetally and laterally in maize (Zea mays L.) root segments placed horizontally; its transport properties are thus similar to those of the growth-inhibiting substances produced by the root cap. The two opposite flows af ABA and of indolyl-3-acetic acid (IAA) — substances both present in the cap — may control elongation and georeaction of the root.
102 citations
TL;DR: The data indicate that no single value of leaf water potential will adequately represent a threshold for stomatal closure in cotton, and that each leaf is uniquely related to its own water potential as modified by age and radiation regime during development.
Abstract: The stomatal resistance of individual leaves of young cotton plants (Gossypium hirsutum L. var. Stoneville 213) was measured during a period of soil moisture stress under conditions of constant evaporative demand. When plants were subjected to increasing soil water stress, increases in stomatal resistance occurred first on the lower leaves and the stomata on the upper surfaces were the most sensitive to decreasing leaf-water potential. Stomatal closure proceeded from the oldest leaves to the youngest as the stress became more severe. This apparent effect of leaf age was not due to radiation differences during the stress period. Radiation adjustments on individual leaves during their development altered the stomatal closure potential for all leaves, but did not change the within-plant pattern. Our data indicate that no single value of leaf water potential will adequately represent a threshold for stomatal closure in cotton. Rather, the stomatal resistance of each leaf is uniquely related to its own water potential as modified by age and radiation regime during development. The effect of age on stress-induced stomatal closure was not associated with a loss of potassium from older leaves. Increases in both the free and bound forms of abscisic acid were observed in water-stressed plants, but the largest accumulations occurred in the youngest leaves. Thus, the pattern of abscisic acid accumulation in response to water stress did not parallel the pattern of stomatal closure induced by water stress.
96 citations
TL;DR: Dose response experiments indicate that GA3 stimulates reversion over a 50–100 fold range with a half maximal response at approximately 0.5 μg GA3 per plant, which is specific for gibberellins as a class of hormones but non-specific for a particular form of gibBerellin.
Abstract: A sensitive and reproducible method to obtain GA3 induced morphological reversion of mature Hedera helix to the juvenile form has been developed Dose response experiments indicate that GA3 stimulates reversion over a 50–100 fold range with a half maximal response at approximately 05 μg GA3 per plant The individual characteristics involved in phase change revert to the juvenile form in a sequential manner as GA3 dose is increased Variations in light intensity from 12–36 × 104 lux and temperature from 15 to 26°C do not affect this hormonal response Other growth regulators including indoleacetic acid, kinetin, abscisic acid and (2-chloroethyl)phosphonic acid (Ethephon) are inactive but other gibberellins (GA1 and a mixture of A4–A7) are active in stimulating reversion Therefore, the response is specific for gibberellins as a class of hormones but non-specific for a particular form of gibberellin The significance of this response in relation to juvenility in woody plants is discussed
95 citations
TL;DR: Water stress does not affect protein synthesis via abscisic acid or reduced hydrostatic pressure, as judged by a double labeling ratio technique.
Abstract: Water stress causes a reduction in hydrostatic pressure and can cause an increase in abscisic acid in plant tissues. To assess the possible role of abscisic acid and hydrostatic pressure in water stress effects, we have compared the effects of water stress, abscisic acid, and an imposed hydrostatic pressure on the rate and pattern of protein synthesis in Avena coleoptiles. Water stress reduces the rate and changes the pattern of protein synthesis as judged by a double labeling ratio technique, Abscisic acid reduces the rate but does not alter the pattern of protein synthesis. Gibberellic acid reverses the abscisic acid-induced but not the stress-induced inhibition of protein synthesis. The effect of hydrostatic pressure depends on the gas used. With a 19: 1 N(2)-air mixture, the rate of protein synthesis is increased in stressed but not in turgid tissues. An imposed hydrostatic pressure alters the pattern of synthesis in stressed tissues, but does not restore the pattern to that found in turgid tissues. Because of the differences in response, we conclude that water stress does not affect protein synthesis via abscisic acid or reduced hydrostatic pressure.
78 citations
TL;DR: The maximum level of ABA occurred approximately 7 weeks after ear emergence (40 d after peak anthesis) and subsequently fell sharply as a result of metabolism of the ABA by the maturing grains.
Abstract: ABA has been determined in wheat grains during their development. The maximum level of ABA occurred approximately 7 weeks after ear emergence (40 d after peak anthesis). This level subsequently fell sharply as a result of metabolism of the ABA by the maturing grains.
73 citations
TL;DR: The results indicate that the leaves, rather than the roots are the site of synthesis of ABA present in the xylem sap of osmotically stressed sunflower plants.
Abstract: Addition of an osmoticum (-12 bars) to the rooting medium of sunflowers (Helianthus annuus L.) caused an increase in the level of abscisic acid (ABA) present in xylem exudate subsequently collected from cut shoots. Using tall and dwarf plants it was shown that there was a time lag in the appearance of increased levels of ABA in tall plants when compared with dwarf plants. The results indicate that the leaves, rather than the roots are the site of synthesis of ABA present in the xylem sap of osmotically stressed sunflower plants.
TL;DR: Tobacco plants pre-exposed to leaf dehydration, mineral deprivation, salination, or BO(3) (3-) toxicity exhibited increased resistance to subzero temperature and to reduced oxygen in the root medium, and a common hormone-regulation mechanism involving abscisic acid is suggested for this phenomenon of "cross-adaptation".
Abstract: Tobacco plants (Nicotiana rustica L) pre-exposed to leaf dehydration, mineral deprivation, salination, or BO33− toxicity exhibited increased resistance to subzero temperature and to reduced oxygen in the root medium The stressed plants all showed an elevated content of leaf abscisic acid Upon transfer of mineral deprived and salinated plants to prestress conditions, a decline in leaf abscisic acid content to prestress levels took place together with a loss of the increased resistance to subzero temperature and to deprivation of root oxygen Treatment with abscisic acid by direct application to the leaves or by addition to the root medium improved leaf resistance to subzero temperature and to deprivation of root oxygen A common hormone-regulation mechanism involving abscisic acid is suggested for this phenomenon of “cross-adaptation” by which a given stress confers increased resistance to other, apparently unrelated stresses
TL;DR: In this paper, free and bound abscisic acid (ABA) levels in blackcurrant and beech buds were determined by an extraction procedure involving several thin-layer chromatography purification stages and final bioassay in the wheat coleoptile straight-growth test.
Abstract: Free and bound abscisic acid (ABA) levels in blackcurrant and beech buds have been determined by an extraction procedure involving several thin-layer chromatography purification stages and final bioassay in the wheat coleoptile straight-growth test. In both species the highest level of free ABA occurs in the autumn at about the time of onset of winter dormancy. The free ABA content then declines throughout the winter months reaching its lowest value just before bud burst. These results strengthen the view that free ABA plays an important role in the induction and maintenance of winter dormancy. The bound ABA level increases in both species throughout the autumn and winter until halfway through the bud swelling phase and then declines. It is proposed that the bound ABA accumulates in the buds because it cannot be translocated or further metabolized during the winter months. The ratios of free to bound ABA were plotted and the resulting curves show a distinctive annual cycle with the highest free ABA/ bound ABA ratio (F/B) occurring in the autumn and the highest bound ABA/ free ABA ratio (B/F) coinciding with bud burst. A gradual increase in the B/F ratio during bud swelling may indicate a feed-back reaction between free and bound ABA which maintains the free ABA at a sufficiently high level to put a gentle brake on growth. At bud burst the B/F ratio falls very sharply and a period of very rapid growth ensues.
TL;DR: The hypothesis that the mode of action of fusicoccin in promoting germination involves, as in stimulation of cell enlargement, the activation at the cell membrane level of proton extrusion processes is supported.
Abstract: Fusicoccin, a toxin stimulating cell enlargement and inducing proton extrusion in various plant tissues, has been shown to replace kinetin, gibberellic acid and red light in breaking seed dormancy. It also removes the inhibitory effect of abscisic acid.
The present data also show that the stimulating effect of fucicoccin on embryo growth of decoated radish (Raphanus sativus L.) and maize (Zea mays) seeds and on the development of maize embryos is accompanied by an early, significant acidification of the medium. Acidification of the medium is also observed when fusicoccin reverses the abscisic acid-induced inhibition of germination. These results support the hypothesis that the mode of action of fusicoccin in promoting germination involves, as in stimulation of cell enlargement, the activation at the cell membrane level of proton extrusion processes.
The physiological significance of fusicoccin-induced release of protons at the onset of germination is discussed in comparison with the results concerning the mechanism of action of fusicoccin on cell enlargement in other plant materials.
TL;DR: Sunflower plants (7 weeks old) were transferred from a modified Hoagland solution to a N-free nutrient medium and kept there for 7 days and it seems unlikely that the roots are responsible for the remarkable increase of the ABA content in the shoots caused by N-deficiency.
Abstract: Sunflower plants (7 weeks old) were transferred from a modified Hoagland solution to a N-free nutrient medium and kept there for 7 days. Abscisic acid (ABA) was determined in several parts of the plants and in exudates collected from the roots of some of these plants.
N-deficiency considerably increased the ABA content of the leaves, especially the older ones, and also considerably increased the ABA content of the upper parts of the stem when compared to the control plants. In the roots and the exudates of these plants no ABA could be detected.
After dissecting the stems the ABA content in the roots of the control plants with normal N supply dropped quickly, probably due to rapid metabolization. Judging by results obtained, it seems unlikely that the roots are responsible for the remarkable increase of the ABA content in the shoots caused by N-deficiency.
TL;DR: Interaction studies with applied hormones indicated that in seeds incubated in the light inhibition by abscisic acid was partially alleviated by N6-benzyladenine but not by GA4/7 application, which may have implications in relation to the involvement of natural plant hormones in the dormancy mechanism of celery seeds.
Abstract: Seeds of five celery (Apium graveolens L.) cultivars germinated at 15°C in the light or dark but at 22°C only in the light. This light requirement was overcome by treatment with a mixture of the gibberellins GA4 and GA7 (GA4/7) but interactions of cytokinins, daminozide, ethephon, EDTA and N-phenyl-N′-4-pyridylurea (NC5392) with GA4/7 were observed. Varietal differences in response to GA4/7 concentration and the requirement for cytokinins were related to the upper temperature limits for germination of the different cultivars. Seeds of cultivars responding to low concentrations of GA4/7 appeared to contain less natural inhibitor than those requiring either high concentrations of GA4/7 or cytokinin in addition to low GA4/7. The cytokinin requirement for germination was partially removed by leaching the seeds with water. Interaction studies with applied hormones indicated that in seeds incubated in the light inhibition by abscisic acid was partially alleviated by N6-benzyladenine but not by GA4/7 application. The implications of these results are discussed in relation to the involvement of natural plant hormones in the dormancy mechanism of celery seeds.
TL;DR: It is suggested that, like soil fungi, the germination of spores of phylloplane fungi may be nutrient-dependent, or independent with respect to exogenous nutrients.
Abstract: Conidia of different isolates of Botrytis cinerea Pers. ex Fr. varied widely in ability to germinate in water. Sugars and amino acids were added at concentrations similar to natural levels on leaf surfaces. To a limited extent simple sugars promoted germination. Fructose was most effective whilst sucrose was least effective. Amino acids stimulated germination with the exception of taurine and lysine. Lysine reduced the stimulatory effect of a mixture of amino acids. Germination of conidia was only increased by an inorganic nitrogen source, ammonium salts or by a mixture of mineral salts, when glucose was present. Growth factors, yeast extract, gibberellic acid and kinetin had no effect on germination but indole-acetic acid caused a small stimulation. Abscisic acid depressed germination. It is suggested that, like soil fungi, the germination of spores of phylloplane fungi may be nutrient-dependent, or independent with respect to exogenous nutrients. Poor in vivo germination of B. cinerea may be associated with competition.
TL;DR: Abscisic acid (ABA) has been identified in the buds and xylem sap of Betula verrucosa (Ehrh.) and Buds also contain esterified ABA.
Abstract: Abscisic acid (ABA) has been identified in the buds and xylem sap of Betula verrucosa (Ehrh.). Buds also contain esterified ABA. In the course of the winter the proportion of esterified ABA in the buds undergoes a progressive increase which may be associated with emergence from dormancy.
TL;DR: Excised stem sections from growing plants of Populus tremula L. and Pisum sativum including lateral buds were treated with indole-3-acetic acid in a phosphate buffer solution and the level of the endogenous auxin decreased strongly and exogenous indoleacetic Acid counteracted the decrease in the inhibitor level to a considerable extent.
Abstract: Excised stem sections from growing plants of Populus tremula L. and Pisum sativum L. including lateral buds were treated with indole-3-acetic acid in a phosphate buffer solution. In control sections the level of the abscisic acid-like inhibitor decreased strongly during 24 h as did the level of the endogenous auxin. Exogenous indoleacetic acid counteracted the decrease in the inhibitor level to a considerable extent. Implications of this auxin effect in relation to apical dominance are discussed.
TL;DR: It was demonstrated that increasing the internal water stress increased the level of endogenous ABA in the phloem–cambial region of bark peelings and decreased the basipetal movement of [14C]IAA through branch sections.
Abstract: In experiments with attached and detached shoots of balsam fir, Abies balsamea L., synthetic (±)abscisic acid (ABA) (1) reduced photosynthesis and transpiration by inducing stomatal closure, (2) inhibited indoleacetic acid (IAA) - induced cambial activity in photosynthesizing and non-photosynthesizing shoots, and (3) inhibited the basipetal movement of [14C]IAA. Neither gibberellic acid nor kinetin counteracted the inhibitory effect of (±)ABA on IAA-induced cambial activity. In addition it was demonstrated that increasing the internal water stress increased the level of endogenous ABA in the phloem–cambial region of bark peelings and decreased the basipetal movement of [14C]IAA through branch sections. On the basis of these findings it is proposed that internal water stress inhibits cambial activity, partly through increasing the level of ABA; the ABA acts to decrease the provision of carbohydrates and auxin that are required for cambial growth.
TL;DR: In this article, the content of abscisic acid (ABA) in Vitis vinifera L. cv was measured by high pressure liquid chromatography and related to bud dormancy.
Abstract: In buds and nodes of Vitis vinifera L. cv. Riesling, the content of abscisic acid (ABA) was measured by high pressure liquid chromatography and related to bud dormancy. In the period of endogenous bud dormancy (rate of bud break is low or zero under favourable climatic conditions) the ABA content increased twelvefold. This indicates a causal relationship between endogenous bud dormancy and ABA.
TL;DR: Applications of ABA to the mature form of Hedera helix stabilize its morphological characteristics and prevent GA3 induced reversion to the juvenile form support the hypothesis that the mature morphological form can be stabilized by regulating the effective level of gibberellins in the plant.
Abstract: Applications of ABA to the mature form of Hedera helix stabilize its morphological characteristics and prevent GA3 induced reversion to the juvenile form. Plants treated with GA3 reverted to the juvenile form whereas those supplied with ABA in conjunction with GA3 remained mature. When mature plants were treated with 5 nanomoles of GA3 and 5 micromoles of ABA, reversion did not occur, but when the GA3 dose was raised to 25 nanomoles with the same level of ABA, reversion did occur. This implies that the relative amounts of GA3 and ABA applied are important in controlling growth form and not the absolute levels of these hormones. Applications of growth retardants (Chlormequat, Ancymidol, and SADH) stabilize the mature form by preventing spontaneous reversions induced under low light intensity. These two lines of evidence support the hypothesis that the mature morphological form can be stabilized by regulating the effective level of gibberellins in the plant and this can be accomplished by inhibition of gibberellin action or gibberellin biosynthesis.
01 Jan 1975
TL;DR: The inability of ethrel to reverse abscisic acid inhibition indicates that kinetin action cannot always be substituted by ethrel, and a combination of the two compounds showed a synergism in polyribosome formation only at high ethrel concentration.
Abstract: The inhibition of germination of Grand Rapids lettuce (Lactuca sativa L.) seeds at 35 C was removed to a marked extent by kinetin and 2-chloroethylphosphonic acid (ethrel). When both compounds were used together, an additive effect was observed. A synergistic effect was, however, noted when ethrel promoted the kinetin reversal of abscisic acid inhibition of seed germination (light- as well as gibberellic acid-, induced). Both kinetin and ethrel increased the total ribosomal material and the percentage of polyribosomes in lettuce seeds imbibed in the light for 24 hours. A combination of the two compounds showed a synergism in polyribosome formation only at high ethrel concentration. The inability of ethrel to reverse abscisic acid inhibition indicates that kinetin action cannot always be substituted by ethrel. The possible mechanisms involved in the enhanced response by a combination of kinetin and ethrel are discussed.
TL;DR: In this paper, the inhibition of germination of Grand Rapids lettuce (Lactuca sativa L.) seeds at 35 C was removed to a marked extent by kinetin and 2-chloroethylphosphonic acid (ethrel).
Abstract: The inhibition of germination of Grand Rapids lettuce (Lactuca sativa L.) seeds at 35 C was removed to a marked extent by kinetin and 2-chloroethylphosphonic acid (ethrel). When both compounds were used together, an additive effect was observed. A synergistic effect was, however, noted when ethrel promoted the kinetin reversal of abscisic acid inhibition of seed germination (light- as well as gibberellic acid-, induced). Both kinetin and ethrel increased the total ribosomal material and the percentage of polyribosomes in lettuce seeds imbibed in the light for 24 hours. A combination of the two compounds showed a synergism in polyribosome formation only at high ethrel concentration. The inability of ethrel to reverse abscisic acid inhibition indicates that kinetin action cannot always be substituted by ethrel. The possible mechanisms involved in the enhanced response by a combination of kinetin and ethrel are discussed.
TL;DR: In this article, the effect of fusicoccin (FC) on ion uptake in barley roots was investigated and the effect was not inhibited by abscisic acid (ABA).
TL;DR: The concentrations of abscisic acid in Grand Rapids lettuce (Lactuca sativa L.) seeds imbibed under conditions which promote or inhibit germination were determined by electron capture-gas chromatography.
Abstract: The concentrations of abscisic acid in Grand Rapids lettuce (Lactuca sativa L.) seeds imbibed under conditions which promote or inhibit germination were determined by electron capture-gas chromatography. The concentration of abscisic acid in dry seeds was 12 to 14 nanograms per 100 milligrams. During 24-hour imbibition, the abscisic acid content diminished more rapidly during conditions which allow germination (25 C in light) than in conditions which inhibited germination (35 C in light or darkness at 25 C). A decrease in endogenous levels of abscisic acid was not always correlated with germination.
TL;DR: ABA cannot, however, induce geotropic curvature in dark-exposed decapped roots, thus confirming that the root cap is the site of graviperception in the intact root.
Abstract: Exogeneous application of abscisic acid (ABA) to intact roots of LG 11 maize seedlings inhibits root elongation and induces bending of the root in response to gravity in darkness, even though the roots of these seedlings are not normally positively geotropic in the dark. ABA cannot, however, induce geotropic curvature in dark-exposed decapped roots, thus confirming that the root cap is the site of graviperception in the intact root.
TL;DR: Excised Pisum sativum L. root tips were incubated in a pH 5.2 sucrose medium containing abscisic acid and stimulation of elongation was not detectable, and increased elongation did not occur in absc isic acid-treated root tips of Lens culinaris L., Phaseolus vulgaris L., or Zea mays L.
Abstract: Excised Pisum sativum L. root tips were incubated in a pH 5.2 sucrose medium containing abscisic acid. Elongation growth was inhibited by 100 μm abscisic acid. However, decreasing the abscisic acid concentration caused stimulation of elongation, the maximum response (25% to 30%) occurring at 1 μm abscisic acid. Prior to two hours, stimulation of elongation by 1 μm abscisic acid was not detectable. Increased elongation did not occur in abscisic acid-treated root tips of Lens culinaris L., Phaseolus vulgaris L., or Zea mays L.