Showing papers on "Abscisic acid published in 1983"
TL;DR: Mutant lines of Arabidopsis thaliana (L.) Heynh, which are characterized by symptoms of withering and the absence of seed dormancy, showed much lower levels of endogenous abscisic acid (ABA) in developing seeds and fruits than the wild type, and it seems that limited access to water is the primary trigger for the developmental arrest in these seeds.
Abstract: Mutant lines of Arabidopsis thaliana (L.) Heynh., which are characterized by symptoms of withering and the absence of seed dormancy, showed much lower levels of endogenous abscisic acid (ABA) in developing seeds and fruits (siliquae) than the wild type. Reciprocal crosses of wild type and ABA-deficient mutants showed a dual origin of ABA in developing seeds. The genotype of the mother plant regulated a sharp rise in ABA content half-way seed development (maternal ABA). The genotype of the embryo and endosperm was responsible for a second ABA fraction (embryonic ABA), which reached much lower levels, but persisted for some time after the maximum in maternal ABA. The onset of dormancy correlated well with the presence of the embryonic ABA fraction and not with the maternal ABA. Dormancy developed in both the absence and presence of maternal ABA in the seeds. In this respect maternal ABA resembled exogenously applied ABA which did not induce dormancy in ABA-deficient seeds. However, both maternal and applied ABA stimulated the formation of a mucilage layer around the testa, which could be observed during imbibition of the mature seeds. In the mature state, ABA-deficient seeds germinated in the siliquae on the plant, but only when the atmosphere surrounding the plant was kept at high relative humidity. In younger stages germination in siliquae occurred after isolation from the plants and incubation on wet filter paper. Therefore, it seems that limited access to water is the primary trigger for the developmental arrest in these seeds.
569 citations
TL;DR: The results suggest that ABA bypasses the cold requirement for hardening and also suggests that A BA triggers the genetic system(s) responsible for inducing the hardening process.
Abstract: The effect of abscisic acid (ABA) on the cold hardiness of cell suspension was investigated. Cell suspension cultures of winter wheat (Triticum aestivum L. cv Norstar), winter rye (Secale cereale L. cv Cougar), and bromegrass Bromo inermis Leyss treated with 7.5 × 10−5 molar ABA for 4 days at 20°C could tolerate −30°C, whereas the control cultures tolerated only −7 to −8°C. The optimum concentration for increasing the cold hardiness of the cultures was 7.5 × 10−5 molar. The degree of cold hardiness and the rate of hardening obtained by ABA treatment was significantly higher than that induced by low temperature alone. Of ten species tested, ABA was only effective on those cultures which were capable of cold hardening upon exposure to low temperatures. The results suggest that ABA bypasses the cold requirement for hardening and also suggests that ABA triggers the genetic system(s) responsible for inducing the hardening process.
305 citations
TL;DR: In this article, monoclonal antibodies have been produced which recognize the physiologically active 2- cis -(S) form of the endogenous plant growth regulator, abscisic acid (ABA).
175 citations
142 citations
TL;DR: Ethylene seems to be involved in the regulation of the senescence of detached rice leaves in relation to their changes in 1-aminocyclopropane-1-carboxylic acid content and ethylene production, which is interpreted to indicate that abscisic acid treatment increased the tissue sensitivity to ethylene, whereas benzyladenine treatment decreased it.
Abstract: The role of ethylene in the senescence of detached rice leaves in relation to their changes in 1-aminocyclopropane-1-carboxylic acid (ACC) content and ethylene production was studied. In freshly excised rice leaf segments, ACC level and ethylene production rates were very low. Following incubation, the rates of ethylene production increased and reached a maximum in 12 h, and subsequently declined. The rise of ethylene production was associated with a 20- to 30-fold increase in ACC level. Ethylene seems to be involved in the regulation of the senescence of detached rice leaves. This conclusion was based on the observations that (a) maximum ethylene production preceded chlorophyll degradation, (b) ACC application promoted chlorophyll degradation, (c) inhibitors of ethylene production and ethylene action retarded chlorophyll degradation, and (d) various treatments such as light, cycloheximide, α,α-dipyridyl, Ni 2+ , and cold temperature, which retarded chlorophyll degradation, also inhibited ethylene production. Abscisic acid promoted senescence but significantly decreased ethylene production, whereas benzyladenine retarded senescence but promoted ethylene production. This is interpreted to indicate that abscisic acid treatment increased the tissue sensitivity to ethylene, whereas benzyladenine treatment decreased it.
112 citations
TL;DR: Though the precise mechanism of fluridone-induced vivipary is unknown, these results indicate that there are important developmental changes occurring at 11 DAP which reversibly commit the immature embryo to v Vivipary or dormancy.
Abstract: Preharvest sprouting or vivipary is induced in developing maize (Zea mays, inbred Tx 5855 and Va 35) seeds by fluridone, a pyridinone inhibitor of carotenoid biosynthesis. Fluridone has a maximal effect on vivipary at 11 days after pollination (DAP) and little effect at 13 DAP in the inbred maize line Tx 5855. Abscisic acid partially reversed the chemically induced vivipary. Though the precise mechanism of fluridone-induced vivipary is unknown, these results indicate that there are important developmental changes occurring at 11 DAP which reversibly commit the immature embryo to vivipary or dormancy.
110 citations
TL;DR: It is proposed that enhancement of abscisic acid metabolism in darkness is mediated by ethylene, as darkness is known to stimulate ethylene production, and may serve as a cumulative indicator of the water stresses to which a particular leaf has been exposed.
Abstract: Metabolism of abscisic acid was compared in stressed and in rehydrated leaf blades of Xanthium strumarium L. Chicago strain that were either detached or left intact on the plant. Under all conditions, phaseic acid was the major metabolite. The high level of phaseic acid that was observed in intact plants 1 day after recovery from stress declined slowly and had not yet reached the prestress level 1 week later. The glucosyl ester of abscisic acid, beta-d-glucopyranosyl abscisate, accumulated at a low rate during periods of prolonged stress. Repeated stress-recovery cycles resulted in a gradual increase in the level of the glucosyl ester, which did not decline following relief of stress for at least 34 days. The level of the glucosyl ester of abscisic acid may therefore serve as a cumulative indicator of the water stresses to which a particular leaf has been exposed.Darkness stimulated abscisic acid metabolism in both detached and attached leaves. Treatment of Xanthium leaves in light with ethylene or chemicals that release ethylene also resulted in a faster breakdown of abscisic acid. Inasmuch as darkness is known to stimulate ethylene production, it is proposed that enhancement of abscisic acid metabolism in darkness is mediated by ethylene.
97 citations
TL;DR: The high conductance of flacca leaves resulted in a high intercellular CO(2) pressure, which allowed greater discrimination against (13)CO(2), as evidenced by more negative delta ( 13)C values for flacca as compared to RR.
Abstract: The relationship between stomatal conductance and capacity for assimilation was investigated in flacca , a mutant of tomato ( Lycopersicon esculentum Mill.) that has abnormal stomatal behavior and low abscisic acid (ABA) content. The assimilation capacity, determined by measuring assimilation rate as a function of intercellular CO 2 pressure, did not differ in leaves of flacca and its parent variety, Rheinlands Ruhm (RR). On the other hand, stomatal conductance of flacca leaves was greater than that of RR, and could be phenotypically reverted by spraying with 30 micromolar ABA. Stomatal conductance of flacca leaves was also reduced by increasing CO 2 pressure, increasing leaf to air vapor pressure difference, and decreasing quantum flux, irrespective of ABA treatment. The high conductance of flacca leaves resulted in a high intercellular CO 2 pressure. This allowed greater discrimination against 13 CO 2 , as evidenced by more negative δ 13 C values for flacca as compared to RR. The δ 13 C values of both flacca and RR plants as influenced by ABA treatment were consistent with predictions based on gas exchange measurements, using a recent model of discrimination.
94 citations
TL;DR: The capacity of the cell walls to undergo acid-induced wall loosening is diminished by ABA-treatment, and the possibility that ABA acts directly by inhibiting growth processes at the cellular level, or indirectly by causing stomatal closure, is discussed.
Abstract: Abscisic acid (ABA) applied to intact bean (Phaseolus vulgaris) leaves or to isolated leaf discs inhibits light-stimulated cell enlargement. This effect may be obtained with 10~4 mol m-3 ABA, but is more significant at higher concentrations. The inhibition of disc expansion by ABA is greater for discs provided with an external supply of sucrose than for discs provided with KC1, and may be completely overcome by increasing the KC1 concentration externally to 50 mol m~3. Decreased growth rate of ABA-treated tissue is not correlated with loss of solutes from growing cells, but is correlated with a decrease in cell wall extensibility. ABA does not prevent light-stimulated acidification of the leaf surface, and stimulates the acidification of the external solution by leaf pieces. However, the capacity of the cell walls to undergo acid-induced wall loosening is diminished by ABA-treatment. The possibility that ABA acts directly by inhibiting growth processes at the cellular level, or indirectly by causing stomatal closure, is discussed.
94 citations
92 citations
TL;DR: Two tomato lines with greatly different capabilities to germinate at 10 degrees C were compared with respect to sensitivity to experimental treatments which affect the water status of the embryo indicating that cold sensitivity is in fact a matter of water relations rather than of phase transitions in membrane lipids.
Abstract: Two tomato (Lycopersicon esculentum Mill.) lines with greatly different capabilities to germinate at 10 degrees C were compared with respect to sensitivity to experimental treatments which affect the water status of the embryo. Germination rates and final percentages could be drastically changed (at 25 degrees C) by (a) removing the mechanical constraint from the radicle tip, (b) imposing water stress by an osmoticum, (c) stress hardening of the seeds through osmotic pretreatment, and (d) inhibiting embryo expansion by abscisic acid (ABA). All treatments showed a similar difference in germination vigor between the two lines indicating that cold sensitivity is in fact a matter of water relations rather than of phase transitions in membrane lipids. Inhibition of germination by ABA was completely abolished by removing the mechanical constraint from the radicle tip. Osmotic stress of -3 bar which quantitatively replaced this constraint in inhibiting germination also restored the sensitivity to ABA. It is concluded that all these treatments act on the balance between the hydraulic extension force of the embryo radicle and the opposing force of the seed layers covering the radicle tip. The difference in cold sensitivity between the two seed lines resides either in the osmotic potential or the pressure potential of the germinating embryo.
TL;DR: The decline in photosynthetic capacity during flooding was largely prevented by supplementary cytokinin applications and spray applications of benzyladenine increased stomatal conductance in both flooded and drained plants.
Abstract: Ethylene, abscisic acid, and cytokinins were tested for their ability to either induce or prevent the changes which occur in gas exchange characteristics of tomato (Lycopersicon esculentum Mill. cv. Rheinlands Ruhm) leaves during short-term soil flooding. Ethylene, which increases in the shoots of flooded plants, had no effect on stomatal conductance or photosynthetic capacity of drained plants. Abscisic acid, which also accumulates in the shoots of flooded plants, could reproduce the stomatal behavior of flooded plants when sprayed on the leaves of drained plants. However, photosynthetic capacity of drained plants was unaffected by abscisic acid sprays. Cytokinin export from the roots to the shoots declines in flooded plants. Spray applications of benzyladenine increased stomatal conductance in both flooded and drained plants. In addition, the decline in photosynthetic capacity during flooding was largely prevented by supplementary cytokinin applications. The possible involvement of these growth substances in modifying leaf gas exchange during flooding is discussed.
TL;DR: The effects of water stress on the levels of ABAGE and its possible physiological role are discussed and some chemical properties of A BAGE are described.
Abstract: Abscisic acid-β-D-glucopyranosyl ester (ABAGE) has been measured in several plant species using 2H-labelled ABAGE as an internal standard. The effects of water stress on the levels of ABAGE and its possible physiological role are discussed. Some chemical properties of ABAGE are described.
TL;DR: It is concluded that, in some cases, ABA may promote leaf growth via its effect on leaf water balance through the involvement of ABA in responses to water stress.
Abstract: The flacca mutant in tomato (Lycopersicon esculentum Mill. cv Rheinlands Ruhm) was employed to examine the effects of a relatively constant diurnal water stress on leaf growth and water relations. As the mutant is deficient in abscisic acid (ABA) and can be phenotypically reverted to the wild type by applications of the growth substance, inferences can be made concerning the involvement of ABA in responses to water stress. Water potential and turgor were lower in leaves of flacca than of Rheinlands Ruhm, and were increased by ABA treatment. ABA decreased transpiration rates by causing stomatal closure and also increased the hydraulic conductance of the sprayed plants. Osmotic adjustment did not occur in flacca plants despite the daily leaf water deficits. Stem elongation was inhibited by ABA, but leaf growth was promoted. It is concluded that, in some cases, ABA may promote leaf growth via its effect on leaf water balance.
TL;DR: Levels of abscisic acid (ABA) in the fruit flesh of developing apples were measured by electron capture gas chromatography and it was found that uptake was higher in discs of outer fruit layers than in discs from inner fruit zones.
Abstract: Levels of abscisic acid (ABA) in the fruit flesh of developing apples (cv. Golden Delicious) were measured by electron capture gas chromatography. ABA content of the tissue, calculated on a fresh weight basis, decreased at a constant rate from 200 ng g_1 in young fruit to 10 fig g-1 in older fruit and then increased when the ripening process commenced. On a whole fruit basis, the ABA level increased during the initial phase of fruit growth, remained constant during the linear growth phase and increased again when fruits started to ripen. During fruit development the ABA content correlated with the rate of sorbitol uptake, when measured after discs of fruit tissue were incubated in [14C]sorbitol. Sorbitol uptake was high during the initial growth phase and declined at a constant rate during fruit development. ABA present in the incubation medium stimulated sorbitol uptake into fruit tissue at concentrations higher than 1CL8 M, whereas indolyl-3-acetic acid had no effect on uptake. When comparing sorbitol uptake in different zones of young fruit, it was found that uptake was higher in discs of outer fruit layers than in discs from inner fruit zones.
TL;DR: The number of spikelets per panicle, number of panicles, percentage filled grains, panicle weight and grain yield per plant and the mobilization and harvest indices were significantly increased by kinetin treatment, while ABA decreased most of them.
Abstract: Senescence of rice (Oryza sativa L. cv. Jaya) leaves was regulated with kinetin and abscisic acid (ABA) sprays at the reproductive stage. The effect of such sprays on grain-filling and yield was analyzed. Spraying 100-day-old plants with kinetin solution (100 μg ml-1) significantly delayed senescence as indicated by higher total chlorophyll and protein levels in the three uppermost leaves compared with the controls. In contrast, spraying with ABA (15 μg ml-1) significantly promoted foliar senescence. The number of spikelets per panicle, number of panicles, percentage filled grains, panicle weight and grain yield per plant and the mobilization and harvest indices were significantly increased by kinetin treatment, while ABA decreased most of them. The possibility of increased grain-filling and thus, yield due to delayed foliar senescence by kinetin treatment and decreased grain-filling due to hastening of senescence by ABA is discussed.
TL;DR: It was calculated that a substantial part of the reduction in leaf net CO(2) uptake (50-80%) could be accounted for by the effect of ABA on stomatal conductance.
Abstract: (±) Abscisic acid (ABA) injected into petioles of attached transpiring leaves of Pharbitis nil Chois. cv violet reduced the photosynthetic capacity of the mesophyll of these leaves as well as the stomatal conductance to CO2 diffusion. Greater than 75% of the injected ABA was recovered as ABA, suggesting that ABA rather than some metabolite thereof was the active compound. The nonstomatal effect of ABA increased from 30% reduction in photosynthesis at 0.25 micromolar ABA in the leaf blade to 90% reduction at 18 micromolar. Despite the effect of ABA on the nonstomatal component of leaf net CO2 uptake, it was calculated that a substantial part of the reduction in leaf net CO2 uptake (50-80%) could be accounted for by the effect of ABA on stomatal conductance.
TL;DR: It is suggested that ABA exerts an effect on the phloem loading of sucrose by enhancing the efflux of suc glucose in leaf discs from castor bean by enhancingThe effect of abscisic acid (ABA) on the uptake of Sucrose by discs from Castor bean cotyledons was investigated.
Abstract: The effect of abscisic acid (ABA) on the uptake of sucrose by discs from castor bean (Ricinus communis L. cv. Zanzibarensis) cotyledons was investigated. Incubation on ABA solutions for one hour or longer significantly inhibited sucrose uptake. The effect was measurable at ABA concentrations as low as 0.1 μM. The inhibition was due to a lowering of the apparent Vmax of the sucrose-carrier system, the Km being unaffected. Uptake of sucrose was coupled to proton uptake but ABA had no detectable effect on the latter process. It is suggested that ABA exerts an effect on the phloem loading of sucrose by enhancing the efflux of sucrose. In leaf discs from three other plant species (Beta vulgaris L., Petunia hybrida L. and Phaseolus vulgaris L.) ABA exerted a similar effect. The results are discussed with respect to source-sink relationships.
TL;DR: The data argue against hypotheses of gravitropism based upon accumulation of ABA to inhibitory levels on the lower side of a hirizontal root based on the finding that the initial effect of A BA on root elongation is stimulatory.
Abstract: Using an auxanometer and time-lapse cinematography we have studied the timing of abscisic acid (ABA) effects on elongation, gravitropic curvature, and hydrogen-ion efflux in several cultivars of maize (Zea mays L.). The effect of high concentrations (e.g. 0.1 mM) of ABA on root elongation is triphasic, including 1) a period of promotion lasting approximately 12 h, 2) a subsequent period of increasing inhibition lasting approximately 12h, and 3) gradual recovery to a rate within approximately 80% of the control rate. With lower concentrations of ABA (e.g. 0.1 μM) only the transient promotive phase is seen. Abscisic acid enhances ethylene biosynthesis in roots of maize but suppression of ethylene biosynthesis does not prevent the long-term inhibitory action of ABA on growth. Application of ABA (0.1 mM) to the upper surface of horizontally placed roots accelerates positive gravitropism. Application of ABA to the lower surface retards gravitropism and in some cases causes the roots to curve upward against the direction of gravity. These observations are consistent with our finding that the initial effect of ABA on root elongation is stimulatory. Since root gravitropism is rapid enough to be completed within the stimulatory phase of ABA action, the data argue against hypotheses of gravitropism based upon accumulation of ABA to inhibitory levels on the lower side of a hirizontal root.
TL;DR: It was found that hardening resulted in an almost 5-fold increase in ABA levels after 3 d at 12 °C, and this decreased to approximately control levels on the fourth day, and the sensitivity of the hardened plants to ABA was greater in terms of rate of closure and amount of ABA required to close the stomata.
Abstract: Leaf abscisic acid (ABA) levels of chilled P. vulgaris were measured after 18 h chilling at 5 °C, at a saturation deficit of 1-24 g m-3 (SD), and after chilling in a water-saturated atmosphere. Changes were also followed during a chill hardening period of 4 d at 12 °C, 2-1 g m~3 SD. It was found that hardening resulted in an almost 5-fold increase in ABA levels after 3 d at 12 °C, and this decreased to approximately control levels on the fourth day. Subsequent chilling of hardened plants produced no change in ABA levels from that of control plants (22 °C). In contrast, non-hardened plants chilled at 1-24 g m-3 SD had ABA levels almost 3 times the level of control plants. However, chilling in a water-saturated atmosphere resulted in a decrease in ABA levels. In addition, the response of leaf diffusion resistance (LDR) to exogenous ABA fed via the transpiration stream was measured at 5 °C and 22 °C in hardened and non-hardened plants. Use of tritium-labelled ABA was made to calculate the stomatal sensitivity to ABA. It was found that exogenous ABA caused an increased in LDR at 22 °C in both hardened and non-hardened plants. However, the sensitivity of the hardened plants to ABA was greater in terms of rate of closure and amount of ABA required to close the stomata. At 5 °C, however, ABA caused stomatal opening and the maintainance of open stomata in non-hardened plants. In hardened plants, ABA caused stomatal closure at 5 °C. These results are discussed in relation to the locking-open response of chilled P. vulgaris stomata.
TL;DR: The fungus Cercospora rosicola has been studied as a model system for abscissic acid biosynthesis, and preliminary results suggest that a similar pathway may operate in plants.
Abstract: The fungus Cercospora rosicola has been studied as a model system for abscissic acid biosynthesis. 1'-dDeoxyabscissic acid and 4'-hydroxy-a-ionylidene acetic acid have been identified as endogenous compounds in this fungus. The results of feeding these and other putative intermediates suggest that abscissic acid biosynthesis proceeds via the successive oxidations of a 3-methyl-5-(2',6',6'-trimethylcyclohex-2'-en-1'-yl)-2,4-pentadienyl intermediate. Preliminary results suggest that a similar pathway may operate in plants.
TL;DR: It is concluded that the destruction of the microtubular network is involved in the development of chilling injury in cotton and abscisic acid greatly reduced this effect of colchicine.
Abstract: The degree of tubulin polymerization in cotton (Gossypium hirsutum L. cv Acala) cotyledonary tissue was estimated by radioimmunoassay which measured the amount of a tubulin-like factor. It was assumed that the release of this tubulin-like factor indicated depolymerization of microtubules. Exposure to chilling resulted in complete release of the tubulin-like factor. Pretreatment with abscisic acid in the light almost completely prevented the chill-induced release of the tubulin-like factor. Addition of colchicine during the chilling period accelerated the release of the tubulin-like factor. Pretreatment with abscisic acid greatly reduced this effect of colchicine. It is concluded that the destruction of the microtubular network is involved in the development of chilling injury in cotton. Abscisic acid apparently decreased chilling injury by stabilization of the microtubular network.
TL;DR: It is suggested that the ABA carrier is an ABA anion/hydrogen ion symport or, less likely, represents facilitated diffusion of undissociated ABA.
Abstract: A carrier for the uptake of abscisic acid (ABA) is present in the tips and elongating zones of primary roots of both leguminous (runner bean, French bean, pea) and non-leguminous (sunflower, maize) seedlings. No ABA carrier was present in more mature root regions. For indole-3-acetic acid both carrier-mediated uptake and a 2,3,5-triiodobenzoate-sensitive efflux component are present in growing and in non-elongating runner-bean root tissues. Both ABA and indole-3-acetic acid carriers were inactivated by protein-modifying reagents. The driving forces for the carrier systems were studied using reagents, (KCl, fusicoccin, vanadate, dicyclohexylcarbodiimide, proton ionophores and azide) known to modify transmembrane pH (ΔpH) and electricla gradients (ΔE) and whose effects were independently monitored using radiolabelled, lipophilic, weak acids as probes. For abscisic acid the carrier-mediated uptake depend on ΔpH and the nonsaturable component of uptake, due to diffusion of undissociated ABA. The maximum velocity of the carrier is greater at pH 4 than at pH 5, although the Michaelis constants are similar. Modification of ΔE did not alter ABA net uptake but effects on the indole-3-acetic acid system consistent with perturbation of an electrogenic 2,3,5-triiodobenzoate-sensitive component were observed. It is suggested that the ABA carrier is an ABA anion/hydrogen ion symport or, less likely, represents facilitated diffusion of undissociated ABA.
TL;DR: In this article, the quantitative changes in abscisic acid (ABA) of achenes during both a stratification period at 4°C and a subsequent germination period at 20°C were investigated.
Abstract: Germination experiments on isolated embryos and intact achenes from Rosa rugosa L. var. rubra revealed the existence of both coat-induced and embryo dormancy. Studies were made on the quantitative changes in abscisic acid (ABA) of achenes during both a stratification period at 4°C and a subsequent germination period at 20°C. Controls were run in parallel at 17°C. Dormant, unimbibed achenes contained large amounts of ABA. The level fell rapidly during the early stages of stratification at 4°C, mainly due to leakage, and then the decline levelled off. The reduction of ABA content during germination was less and followed a tri-phasic pattern. Under the control conditions, the ABA level also fell although still faster, the amounts present being consistently below those detected in the corresponding cold-stratified samples. The content of alkali-hydrolysable ABA was low and not affected either by the duration or by the temperature of stratification. The investigation shows that termination of dormancy is not simply a consequence of a fall in the content of endogenous ABA and supports the current debate questioning the central role of ABA in regulation of dormancy breakage and of germination.
TL;DR: Endogenous abscisic acid content (ABA) of Arbutus unedo leaves growing under natural conditions in a macchia near Sobreda, Portugal, was very high and the effectiveness with which injected ABA closed stomata was highest during the morning and decreased substantially at midday.
Abstract: Endogenous abscisic acid content (ABA) of Arbutus unedo leaves growing under natural conditions in a macchia near Sobreda, Portugal, was very high (0.25 to 2.3 μg g1 fresh weight). Highest concentrations were found during the very early morning hours and at midday. During the late morning hours and in the late afternoon ABA concentrations decreased to between one-third and one-fourth of peak values. The samples for ABA content were obtained from both irrigated (Ψ between-10 and-25 bar) and non-irrigated plants experiencing natural water stress during the dry season (Ψ of-50 bar). During the course of the measurement day, stomatal conductance was relatively constant and conductance of watered plants was 50 to 100% greater than that of unwatered plants. No clear correlations between ABA content and stomatal conductance and/or xylem water potential were observed. Despite large differences in water potential and differences in degree of stomatal opening, absolute concentrations of ABA were not found to differ.
TL;DR: Growth and differentiation of haploid gametophytes of the fern Ceratopteris are influenced by antheridiogen and abscisic acid, and meristem development is often submarginal or central in the presence of absc isic acid and results in the formation of cup-shaped female gametology bearing archegonia.
Abstract: Growth and differentiation of haploid gametophytes of the fern Ceratopteris are influenced by antheridiogen and abscisic acid. Antheridiogen induces the premature formation of male sex organs (antheridia), while abscisic acid, at a concentration of 10−4 M, completely blocks antheridia formation, even in the presence of antheridiogen. In addition, abscisic acid stimulates rhizoid production at concentrations of 10−6–10−5 M but becomes inhibitory at higher concentrations. Meristem development, which is normally at the margins of gametophytes, is often submarginal or central in the presence of abscisic acid and results in the formation of cup-shaped female gametophytes bearing archegonia.
TL;DR: The data indicate that water stress does not only affect ABA synthesis and metabolism, but also ABA distribution between symplast and apoplast and between various leaf tissues.
TL;DR: The abscisic acid (ABA) effect on root elongation is first reported comparing intact roots and apical root segments (prepared from primary roots of LG11 maize) treated 1 h by buffered ABA then kept 5 h in the dark (humid air or in buffered medium).
TL;DR: It appears that most but not all of the new proline synthesized due to stress is located in the cytoplasmic compartment, and Potassium might have a special role in controlling internal events in pea shoots.
Abstract: The response of pea plants (Pisum sativum L.) to the presence of 192 mM NaCl or of 10-5 abscisic acid (ABA) was similar: shoot growth was inhibited, internal osmolarity and the content of organic solutes increased, and proline accumulated. It appears that most but not all of the new proline synthesized due to stress is located in the cytoplasmic compartment. The responses of the plant to salinity and externally applied ABA differed, apparently, in the mechanism of adjustment of the internal osmolarity: mainly ion absorption in the first, mainly synthesis of organic osmotica in the second. Potassium might have a special role in controlling internal events in pea shoots. Increase in the internal ABA content may serve as a trigger for the changes in pea shoots, but the sequence of events in pea roots may be different; the trigger may be some mechanism other than ABA accumulation. In this study ABA had no effect on root growth.