Action of Abscisic Acid on Ion Transport as Affected by Root Temperature and Nutrient Status

Measurements were made of the transport of ions through excisedbarley roots. It is shown that addition of 10^–5 M abscisicacid (ABA) may lead to inhibition or stimulation of transport.The effect of ABA depended on the conditions in which the plantshad been grown and on the temperature at which the experimentwas carried out. It is suggested that stimulation of transportis a direct effect of ABA, but inhibition may be an indirecteffect due to disturbance of endogenous levels of plant hormones.The results are considered in relation to regulation of iontransport in the plant as a whole.     

Exogenous Catalase and Ascorbate Modify the Effects of Abscisic Acid (ABA) on Root Hydraulic Properties in Phaseolus vulgaris L. Plants

Abscisic acid (ABA) modifies the hydraulic properties of roots by increasing root water flux (J_v). The role of reactive oxygen species (ROS) in this ABA-induced process was evaluated. At the same time, some antioxidant enzyme activities in root tissues were measured. Phaseolus vulgaris plants were grown hydroponically, and different concentrations of ABA in combination with catalase enzyme or ascorbate were added to the nutrient solution. Catalase treatment had no effect by itself (no ABA) and had little or only a small stimulatory effect at ABA concentrations of 1, 50, and 100 μM, but it partially inhibited the ABA effect at 5 μM. Ascorbate by itself doubled J_v and root hydraulic conductance over the control value. In the presence of ABA, ascorbate partially or, at 100 μM, completely inhibited that ABA stimulation of J_v. These results are discussed in relationship to the possibility that ABA signaling in the roots involves ROS.     

Temperature-Dependent Water and Ion Transport Properties of Barley and Sorghum Roots : II. Effects of Abscisic Acid

Water flux through excised roots (J_v) is determined by root hydraulic conductance (L_p) and the ion flux to the xylem (J_i) that generates an osmotic gradient to drive water movement. These properties of roots are strongly temperature dependent. Abscisic acid (ABA) can influence J_v by altering L_p, J_i, or both. The effects of root temperature on responses to ABA were determined in two species differing in their temperature tolerances. In excised barley (Hordeum vulgare L.) roots, J_v was maximum at 25°C; 10 micromolar ABA enhanced J_v, primarily by increasing L_p, at all temperatures tested (15-40°C). In sorghum (Sorghum bicolor L.) roots, J_v peaked at 35°C; ABA reduced this optimum temperature for J_v to 25°C by increasing L_p at low temperatures and severely inhibiting J_i (dominated by fluxes of K⁺ and NO₃⁻) at warm temperatures. The inhibition of K⁺ flux by ABA at high temperature was mostly independent of external K⁺ availability, implying an effect of ABA on ion release into the xylem. In sorghum, ABA enhanced water flux through roots at nonchilling low temperatures but at the expense of tolerance of warm temperatures. These effects imply that ABA may shift the thermal tolerance range of roots of this heat-tolerant species toward cooler temperatures.     

Rapid Effects of Abscisic Acid on Ion Uptake in Sunflower Roots

Short-term effects of ABA, ABA + kinetin and kinetin on ion (⁸⁶Rb-potassium and phosphate) and water uptake in sunflower plants (Helianthus annuus var. californicus) were examined with a continuous-recording technique. Ion uptake in the roots and transport to the shoots were also investigated by conventional tracer uptake experiments and by sap bleeding experiments with excised roots. After addition of 5 × 10^?6-4 × 10^?5M ABA to the root medium there was an immediate decrease (30–70%) in the rate of ion uptake which lasted 30–70 min. The rate of water uptake was not significantly affected as measured with this method. Ion transport to the shoots and to the bleeding sap of excised roots was decreased by ABA. ABA-induced inhibition of ion uptake was abolished by the presence of kinetin, and uptake was slightly stimulated by 2 × 10^?5M kinetin alone. We suggest that concentration gradients of ABA or rapid changes in the ABA-kinetin balance in the roots affect ion uptake and transport.     

Abscisic Acid Action on Basipetal Auxin Transport

Several experiments have been performed to analyse the ABA effects on the basipetal transport of IAA-2-¹⁴C, using sections of epicotyls prepared from etiolated Lens seedlings. The sections were incubated in an ABA solution or ABA was applied in the donor blocks containing IAA. For each type of assay, the uptake (analyses of the donor blocks) and the movement of IAA-C¹⁴ (analyses of the receiver blocks) were inhibited by ABA. The distribution of continuous decrease of the radioactivity, along the sections' axis, showed a ¹⁴C level from the apical towards the basal segments. ABA caused a decrease in the ¹⁴C concentration for the total sections, but a relative increase for the basal segment. When ABA was applied simultaneously with IAA in the donor blocks, the transport velocity of IAA, through the sections, was not changed significantly, while an ABA pretreatment caused a significant decrease.     

Effects of Fusicoccin and Abscisic Acid on Sugar and lon Transport from Plant Glands

Fusicoccin (FC) inhibited net excretion of Cl^– by theglands of the pitchers of the carnivorous plant Nepenthes hookeriana;of Na⁺ and Cl^– by the salt glands of the halophytes Limoniumvulgare and L. pectinatum and of K⁺ in the nectar of Acer platanoidesflowers. It had no effect on K⁺ elimination with nectar of Impatienswalleriana (extrafloral nectaries) and Abutilon striatum. Abscisicacid (ABA) stimulated net excretion of K⁺ and Cl^– in Nepenthesand of Na⁺ and Cl^– in Limonium but had no effects on K⁺in nectar. Thus, FC and ABA had opposing effects on ion excretionby the salt eliminating glands of Limonium and Nepenthes. Bothcompounds, however, had similar effects on sugar secretion ofnectary glands which was either inhibited or unaffected by FCand ABA. It is suggested that the effects of FC and ABA on ion excretionby gland cells could be reconciled with literature showing FC-stimulationand possible ABA-inhibition of proton pumps at the plasmalemmaof plant cells. Nepenthes hookeriana, Limonium vulgare, Limonium pectinatum, Acer platanoides, salt-glands, nectaries, excretion, fusicoccin, abscisic acid, proton pump     

Carbon Transport and Root Respiration of Split Root Systems of Phaseolus vulgaris Subjected to Short Term Localized Anoxia

The influence of anoxia on carbon transport and root respiration was evaluated by applying [U-¹⁴C]sucrose to the foliage. Translocation patterns to the root systems of two dry edible bean genotypes (Phaseolus vulgaris L.) were examined after a 3-day exposure to aerated and nonaerated environments. Localized anoxia of root systems was simulated by growing roots in split configurations and exposing half of the system to anoxic conditions. Anoxia of the root system for 72 hours reduced the movement of ¹⁴C label into the roots with concurrent accumulations in the hypocotyl region. The translocation of ¹⁴C label to anoxic roots was less than 50% of the aerated controls of both genotypes. Most of the ¹⁴C label translocated to anoxic root systems was excluded from respiratory metabolism during the 3-hour pulse/chase period and was an order of magnitude less than the aerated controls. These observations suggest that the bulk of ¹⁴C label which entered the root during the anoxic period was unavailable for metabolism by the enzymes of glycolysis and/or was diluted by a relatively large metabolite pool. A higher percentage of ¹⁴C label was translocated to the aerated half of the localized anoxia treatment relative to the half of the aerated controls. The proportion of ¹⁴C label translocated to the root system in the aerated control was 20 and 16% compared to 28 and 25% in the aerated localized anoxia treatment for the genotypes Seafarer and line 31908, respectively. Line 31908 partitioned a greater percentage of ¹⁴C-labeled compounds to the actively growing fraction of the root system in the localized anoxia treatment than did Seafarer. This suggests a greater reliance on previously stored carbohydrate for immediate root growth in Seafarer than in line 31908.     

Effects of Ca on Amino Acid Transport and Accumulation in Roots of Phaseolus vulgaris

Ca²⁺ stimulates the uptake of α-aminoisobutyric acid (AIB) into excised or intact Phaseolus vulgaris L. roots by a factor of two. In roots depleted of Ca²⁺ by preincubation with ethylenediaminetetraacetate, ethyleneglycol-bis(β-aminoethyl ether)-N,N′-tetraacetic acid, or streptomycin, the stimulatory effect is 7- to 10-fold. In the presence of Ca²⁺, roots accumulate AIB more than 100-fold; Ca²⁺-depleted roots only equilibrate with AIB. Radioautography shows [¹⁴C]AIB to be present in all cells after 90 min. Although Ca²⁺-depleted roots lose accumulated [¹⁴C]AIB about 10 times faster than roots supplied with Ca²⁺, this increased efflux is not the main cause for the decrease in net uptake observed. The latter is rather due to a less negative membrane potential Δψ in Ca²⁺ depleted roots (−120 mV → −50 mV). The basic feature explaining all the results of Ca²⁺ deficiency is an increase in general membrane permeability. No indication of a specific regulatory function of Ca²⁺ in membrane transport of roots has been obtained.     

Abscisic Acid Accumulation in Developing Seeds of Phaseolus vulgaris L

Free and bound abscisic acid (ABA) in the pod, seed coat, and embryo were determined separately throughout seed development of Phaseolus vulgaris L. cv. `Taylor's Horticultural.' An internal standard method of gas-liquid chromatography was used for ABA quantification. In the embryo, two peaks of free ABA occurred at days 22 (1.18 micrograms per gram or 5.5 micromolar) and 28 (1.74 micrograms per gram or 12 micromolar); and a single peak of bound ABA at day 30. In the seed coat, there was one peak of free ABA at day 22 and only small amounts of bound ABA. Very small amounts of ABA were detected in the pod at any stage of development. In cv. PI 226895, in which seed development is more rapid than in `Taylor's Horticultural,' the embryo ABA peaks occur on days 20 and 26. The timing of the ABA peak in the embryo, and the concentration attained, are consistent with previous reports on the natural pattern of RNA synthesis and with ABA inhibition of RNA synthesis in developing bean fruit.     

Root and Shoot Growth of Plants Treated with Abscisic Acid

Young seedlings of Capsicum annum L., Commelina communis L.and maize (Zea mays L.) were subjected to a mild water-stressingtreatment and/or treated with abscisic acid (ABA). Plants rootedin soil received a soil-drying treatment and their leaves weresprayed with a 10–⁴ M solution of ABA. Plants grown insolution culture were stressed by the addition of polyethyleneglycol (PEG) to the rooting medium and ABA was also added tothe rooting medium, either with or without PEG. The effectsof both treatments on the growth of roots and shoots and theultimate root: shoot dry weight ratio were very similar. Shootgrowth was limited both by water stress and by ABA application;while there was some evidence that mild water stress and/orABA application may have resulted in a stimulation of root growth.More severe water stress reduced the growth of roots but theoverall effect of stress was to increase the ratio of rootsto shoots. Capsicum annum L., Commelina communis L., Zea mays L., water stress, abscisic acid     

Triadimefon Protects Bean Plants from Water Stress through its Effects on Abscisic Acid

Triadimefon is a fungicide that has plant growth regulatingproperties. In beans (Phaseolus vulgaris L.) it significantlyreduced shoot weight, shoot length and leaf area, and rootsappeared whiter and thicker in the treated plants. Chlorophylland carotenoid levels were increased in the leaves, but triadimefondid not affect protein levels in either leaves or roots. Triadimefonreduced transpiration and protected the plants from drought.It increased leaf diffusive resistance indicating partial closureof the stomates, and treated plants maintained their water potentialswhile those of the controls declined. Osmotic potentials ofboth treated and control leaves fell, but values in the controlswere significantly lower than those from the treated plants.Three days after treatment with triadimefon in both water stressedand non-stressed plants the abscisic acid levels in the leavesof the treated plants were more than twice the levels of thecontrols. It appears therefore that the protection conveyedby triadimefon during water stress is mediated at least partially,via its effects on ABA levels in treated tissue. (Received October 12, 1985; Accepted January 8, 1986)     

Inhibition of Ion Transport in Excised Barley Roots by Abscisic Acid; Relation to Water Permeability of the Roots

Previous papers have shown that abscisic acid can inhibit transportof ions across the root to the xylem vessels, resulting in reducedexudation from excised roots or inhibiting guttation from intactplants. However, it has not been established whether the inhibitionwas due to a reduction in salt transport (J_s) or in permeabilityof the roots to water (L_p). This paper investigates the effectof ABA on L_p and J_s separately. It is shown that L_p increasedin ABA and then fell, but was about the same as in control rootswhen transport was inhibited. The effect of ABA on exudationtherefore appeared to be mainly due to reduction in J_s. Inhibitionof J_s was also present in intact, transpiring plants and sowas not due to reduced water flow. The inhibition of ion releaseto the xylem affected Na⁺, Mg²⁺, Ca²⁺, and phosphate as wellas the major ion in the exudate, K⁺. It is concluded that ABAinhibits salt transport to the shoot by acting on ion transportinto the xylem, and not by reducing water flow coupled withsalt transport.     

Action of Abscisic Acid on Auxin Transport and its Relation to Phototropism

The action of abscisic acid on the kinetics of auxin transport through Zea mays L. (cv. Goudster) coleoptiles has been investigated. Abscisic acid applied simultaneously with indoleacetic acid-2-¹⁴C in the donor block reduced the transport intensity without materially affecting the basipetal velocity or the uptake. No effect on acropetal transport was observed. The data have been used to discuss the similarities in effects of abscisic acid and visible radiation and a hypothesis is proposed to explain the phenomena of phototropism.     

Bioproduction of Ascorbic Acid in Root Nodule and Root of the Legume Pulse Phaseolus mungo

The root nodules of Phaseolus mungo (L.), a herbaceous leguminous pulse, contain high amounts of ascorbic acid (AsA). A glucose pool present in the nodule might serve as precursor for AsA production. From root nodule, a Rhizobium sp. was isolated. The symbiont produced a large amount of AsA (290.5 μg/ml) from glucose-supplemented basal medium. The production of AsA by the symbiont was much greater than that of the control when the glucose (0.5%)-supplemented mineral medium was enriched with thiamine hydrochloride (20 μg/100 ml), biotin (20 μg/100 ml), and L-asparagine (0.2%). The possible role of the rhizobial production of AsA on rhizobia–legume symbiosis is discussed.     

Effect of Fruits on Dormancy and Abscisic Acid Concentration in the Axillary Buds of Phaseolus vulgaris L

The mechanism regulating the growth of adult plants in two determinate bean (Phaseolus vulgaris L.) cultivars was investigated. “Redkloud” plants flowered, formed fruits, and ceased shoot growth earlier than “Redkote” plants. Redkloud attained a smaller plant size, compared to Redkote, by imposing dormancy on axillary buds at an earlier age. In both cultivars, cessation of bud growth coincided with maximum combined fruit length per plant. Removal of fruits caused resumption of axillary bud growth within 4 to 5 days. The amount of new growth induced by fruit removal depended on the cultivar and plant age. In fully developed Redkloud plants, where shoot growth had already ceased, total leaf and shoot number per plant nearly doubled within 2 weeks following fruit removal. A much smaller response was observed in the still growing Redkote plants. Fruits, therefore, are assumed to play a major role in the regulation of shoot growth and total plant size through the control of axillary bud dormancy. It seems that smaller plant size, earlier maturity, and earlier senescence of Redkloud, compared to Redkote, were the result of earlier flowering, and accomplished in part through the growth-inhibiting action of fruits.     

不同营养物质对脱落酸液体发酵产量的影响

考察了不同营养添加物及前体对脱落酸 (abscisicacid ,ABA)液体发酵的影响。在玉米粉、黄豆饼粉、燕麦、小米粉等不同营养添加物中 ,以添加玉米粉效果较好 ,产量可提高 35 .8% ;将碳源由单一的葡萄糖改变为蔗糖∶葡萄糖 =3∶2 ,可使产量提高 6 8.8% ;而在乙酸钠等二碳至五碳原子的不同前体添加物中 ,乙酸钠、丙酮酸钠、丁二酸钠、柠檬酸三钠盐等能提高脱落酸产量 ,而丙酸钙、氨基乙酸对脱落酸的生成有抑制作用 ,尤其是柠檬酸三钠盐对脱落酸产量影响最为显著 ,可使产量比对照提高 81.0 %。     

Effects of Abscisic Acid and of Hydrostatic Pressure Gradient on Water Movement through Excised Sunflower Roots

The effect of abscisic acid on the exudation rate from decapitated roots of sunflower plants (Helianthus annuus L.) was investigated in the presence and absence of an imposed hydrostatic pressure gradient. The magnitude of the abscisic acid effect was constant even when suctions up to 60 cm Hg were applied to the cut stumps.     

脱落酸不同处理时间对丹参毛状根有效成分积累的影响

采用HPLC测定脱落酸(abscisic acid,ABA)处理1、3、6、9 d后丹参毛状根中丹参酮I、隐丹参酮、二氢丹参酮I、丹参酮IIA含量的方法,研究不同ABA处理时间对丹参酮类成分积累的影响。结果表明:①随着ABA处理时间的增加,丹参毛状根生长受到抑制逐渐减弱,并在处理6 d左右变的不显著;②毛状根中四种丹参酮的产量和含量均在ABA处理6 d左右趋于稳定。其中丹参酮I、隐丹参酮、二氢丹参酮I和丹参酮II的产量分别提高为空白对照组的4.65、7.80、18.33和2.11倍;③三种丹参酮类合成抑制剂均对丹参毛状根的生长、丹参酮类的合成有抑制作用。     

Abscisic Acid Elicits the Water-Stress Response in Root Hairs of Arabidopsis thaliana

Water stress has been shown to cause root hairs to become short and bulbous. Because abscisic acid (ABA) mediates a variety of water-stress responses, we investigated the response of Arabidopsis thaliana root hairs to ABA. When wild-type root hairs were treated with ABA, they exhibited the water-stress response. The Arabidopsis mutants abi1 and abi2, which are insensitive to ABA at the seedling stage, did not display the root hair response. These data suggest that ABA may mediate the response of root hairs to water stress. The drought response of root hairs resulting in an inhibition of tip growth will provide an easy screen to select mutations that are insensitive to ABA and/or involved in tip growth.     

光亲和标记鉴定玉米根脱落酸结合蛋白

光亲和标记鉴定玉米根脱落酸结合蛋白吴忠义,陈珈,朱美君（北京农业大学生物学院,１０００９４）关键词结合蛋白;光亲和标记;ＡＢＡ;受体;微粒体脱落酸（ＡＢＡ）作为一大类植物激素,在高等植物的生长发育以及对逆境的适应过程中发挥着重要作用。在探讨激素作用的...