scholarly journals Uptake and Release of Abscisic Acid by Isolated Photoautotrophic Mesophyll Cells, Depending on pH Gradients

1981 ◽  
Vol 68 (1) ◽  
pp. 202-206 ◽  
Author(s):  
Werner M. Kaiser ◽  
Wolfram Hartung
Keyword(s):  
Abscisic Acid ◽  
Mesophyll Cells ◽  
Ph Gradients ◽  
Uptake And Release

Uptake and Release of Abscisic Acid by Runner Bean Root Tip Segments

1983 ◽  
Vol 38 (9-10) ◽  
pp. 719-723 ◽  
Author(s):  
Wolfram Hartung ◽  
Barbara Dierich
Keyword(s):  
Abscisic Acid ◽  
Uptake Rate ◽  
Root Tip ◽  
Root Tips ◽  
Root Cells ◽  
Ph Gradients ◽  
External Ph ◽  
Uptake And Release ◽  
Stimulation Of ◽  
Undissociated Molecule

Uptake of abscisic acid by 5 mm long decapped root tips is a linear function of the external ABA concentration in the range of 2.9 × 10-8m to 10-4м and decreases dramatically with in­creasing pH. At pH 8.0 uptake rate is extremely low, even at high ABA concentrations. This indicated that nearly all of the ABA is taken up as the undissociated molecule ABAH. Uptake of ABA is influenced by agents modifying the pH gradients between the medium and the tissue such as salts of weak acids incubated at low external pH (inhibition of uptake and stimulation of ABA release by abolishing the pH gradients), protonophores such as CCCP (inhibition of uptake) and fusicoccin (stimulation of uptake by increasing the pH between medium and cytoplasm). It is concluded that ABA distributes between the compartments of the root cells according to the pH gradients with the undissociated molecule as the only penetrating species. Uptake and release occur without participation of a saturable component by diffusion. In contrast IAA permeates the plasmalemma as both IAAH and IAA-.

The site of abscisic acid metabolism in mesophyll cells of Spinacia oleracea

1980 ◽  
Vol 18 (4) ◽  
pp. 359-364 ◽  
Author(s):  
W. Hartung ◽  
H. Gimmler ◽  
B. Heilmann ◽  
G. Kaiser
Keyword(s):  
Abscisic Acid ◽  
Acid Metabolism ◽  
Spinacia Oleracea ◽  
Mesophyll Cells ◽  
Abscisic Acid Metabolism

The Site of Indole-3-acetic Acid Synthesis in Mesophyll Cells of Spinacia oleracea

1982 ◽  
Vol 37 (3-4) ◽  
pp. 174-178 ◽  
Author(s):  
B. Heilmann ◽  
W. Hartung ◽  
H. Gimmler
Keyword(s):  
Acetic Acid ◽  
Abscisic Acid ◽  
Acid Treatment ◽  
Spinacia Oleracea ◽  
Intracellular Localization ◽  
Acid Synthesis ◽  
Acid Biosynthesis ◽  
Mesophyll Cells ◽  
Indole 3 Acetic Acid

Abstract Using [14C]tryptophan as a precursor, the intracellular localization of indole-3-acetic acid biosynthesis in spinach mesophyll cells was investigated. Chloroplasts as well as extraplastidic compartments were able to transform tryptophan into indole-3-acetic acid.The cofactor requirement of plastidic and extraplastidic indole-3-acetic acid synthesis is shown.Light and abscisic acid treatment inhibited preparations.

The Permeability Coefficients of the Plasmalemma and the Chloroplast Envelope of Spinach Mesophyll Cells for Phytohormones

1981 ◽  
Vol 36 (7-8) ◽  
pp. 672-678 ◽  
Author(s):  
H. Gimmler ◽  
B. Heilmann ◽  
B. Demmig ◽  
W. Hartung
Keyword(s):  
Molecular Weight ◽  
Abscisic Acid ◽  
Gibberellic Acid ◽  
Mevalonic Acid ◽  
Chloroplast Envelope ◽  
Mesophyll Cells ◽  
Permeability Coefficients ◽  
Intact Chloroplasts ◽  
Acid Lactone ◽  
External Ph

Abstract The uptake of auxin (LAA), abscisic acid (ABA) the synthetic cytokinin benzylaminopurine (BA), gibberellic acid (GA3) and mevalonic acid (lactone) (MVA) into intact chloroplasts and protoplasts from spinach mesophyll cells was measured and the permeability coefficients Ps of the chloroplast envelope and the plasmalemma were calculated. With all solutes tested uptake and P s values were considerably higher in the chloroplast system than in the protoplast system. At an external pH of 7.0, rates of uptake exhibited the order BA > LAA > MVA > ABA > GA3 in both systems. However, the P s values (corrected for the undissociated species of the solutes) exhibited the order LAA > GA3 > (ABA or BA) > MVA. This corrected sequence indicates the theoretical capacity of penetration under the assumption that preferentially the protonated species of phytohormones are capable of readily penetrating membranes. P s values for phytohormones appeared largely to be determined by the distribution coefficient K d and to a lesser extent by the molecular weight (Mr). In the Collander-plot the relation between the logarithm of Ps values for phytohormones and some other solutes such as acetate, glycerol, glucose, sorbitol and sucrose and the logarithm of K J M T 1.5 approached linearity.

scholarly journals Abscisic acid signalling determines susceptibility of bundle sheath cells to photoinhibition in high light-exposed Arabidopsis leaves

2014 ◽  
Vol 369 (1640) ◽  
pp. 20130234 ◽  
Author(s):  
Magdalena Gorecka ◽  
Ruben Alvarez-Fernandez ◽  
Katie Slattery ◽  
Lorna McAusland ◽  
Phillip A. Davey ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Bundle Sheath ◽  
High Light ◽  
Major Influence ◽  
Photochemical Quenching ◽  
Mesophyll Cells ◽  
Specific Expression ◽  
Rapid Induction ◽  
Vascular Parenchyma ◽  
Photosynthetic Responses

The rapid induction of the bundle sheath cell (BSC)-specific expression of ASCORBATE PEROXIDASE2 ( APX2 ) in high light (HL)-exposed leaves of Arabidopsis thaliana is, in part, regulated by the hormone abscisic acid (ABA) produced by vascular parenchyma cells. In this study, we provide more details of the ABA signalling that regulates APX2 expression and consider its importance in the photosynthetic responses of BSCs and whole leaves. This was done using a combination of analyses of gene expression and chlorophyll a fluorescence of both leaves and individual BSCs and mesophyll cells. The regulation of APX2 expression occurs by the combination of the protein kinase SnRK2.6 (OST1):protein phosphatase 2C ABI2 and a Gα (GPA1)-regulated signalling pathway. The use of an ost1-1/gpa1-4 mutant established that these signalling pathways are distinct but interact to regulate APX2 . In HL-exposed leaves, BSC chloroplasts were more susceptible to photoinhibition than those of mesophyll cells. The activity of the ABA-signalling network determined the degree of susceptibility of BSCs to photoinhibition by influencing non-photochemical quenching. By contrast, in HL-exposed whole leaves, ABA signalling did not have any major influence on their transcriptomes nor on their susceptibility to photoinhibition, except where guard cell responses were observed.

Light-Induced pH Gradients in Isolated Spinach Chloroplasts

1976 ◽  
Vol 3 (2) ◽  
pp. 141 ◽  
Author(s):  
WS Chow ◽  
AB Hope
Keyword(s):  
Fluorescence Quenching ◽  
External Medium ◽  
Chloride Ions ◽  
Buffering Capacity ◽  
Small Decrease ◽  
Ph Gradients ◽  
Actinic Light ◽  
Ionic Relations ◽  
Kinetics Of ◽  
Uptake And Release

The fluorescence quenching of certain fluorescent, weakly ionizing amines has been used to estimate the pH difference (ΔpH) between the intrathylakoid spaces of chloroplasts and the external medium under various conditions. The amines N-(1-naphthyl)ethylenediamine and 9-aminoacridine gave consistent and similar estimates of ΔpH provided the concentration ranges 0.25 - 2 μM and 0.05 - 0.5 μM, respectively, were not exceeded. Values for ΔpH of up to 4 units were estimated for control chloroplasts. Only a small decrease in ΔpH was caused by FCCP and DCMU concentrations that decreased photophosphorylation rates to 10-20% of control. The kinetics of the onset and decay of ΔpH, and of the uptake and release of protons by the chloroplasts, were followed after the sudden application or withdrawal of actinic light. These kinetics suggest a model for the ionic relations of stripped chloroplasts with internal buffering capacity, [α], and dissociation constant, Ka, as parameters. At pH8, [α] is about 80 mol m-3 and Ka is 0.07 mol m-3 (pKa = 4.15). The model is successful in predicting the relation between [H+]I (the internal proton concentration) and ΔH+o (the light-driven uptake of protons from the external medium), as well as the size of ΔH+o , but needs extending to deal with published experiments on the light-driven translocation of chloride ions.

The pH gradients in the root system and the abscisic acid concentration in xylem and apoplastic saps

1993 ◽  
Vol 341 (1295) ◽  
pp. 49-56 ◽  
Keyword(s):  
Plasma Membrane ◽  
Abscisic Acid ◽  
Root System ◽  
Free Acid ◽  
Stomatal Closure ◽  
Xylem Sap ◽  
Cytosolic Ph ◽  
Root Cells ◽  
Ph Gradients ◽  
Stress Signal

Abscisic acid (ABA) is a stress signal that is transported from the root system to leaves, and induces stomatal closure before water relations of the leaves are affected by soil drying. Xylem vessels are in direct contact with the leaf apoplasm, the only leaf compartment that is directly connected with the primary site of ABA action, the outer surface of the guard cell plasma membrane (Hartung 1983). ABA distributes among the leaf compartments according to the anion trap concept and the Henderson-Hasselbalch equation, with the free acid as the permeating and the anion as the nearly non-permeating molecular species. Applying this concept, a flattening of the intracellular pH gradients increases the apoplastic ABA concentration. Indeed, stress increases the apoplastic pH (Hartung et al. 1988) and decreases slightly the cytosolic pH . The validity of this concept has been shown repeatedly and was confirmed by a mathematical leaf model (Slovik et al. 1992). It is appropriate to ask whether these mechanisms also contribute to ABA compartmentation and redistribution in the root system. Therefore, we have incorporated compartmental pH values of unstressed and stressed root cells, the permeability coefficients of root membranes for ABA and anatomical data into a mathematical model, similar to that of Slovik et al. (1992). The simulation shows that ABA redistribution in roots caused by changing pH gradients can account for up to a 2 to 3-fold accumulation of ABA in the xylem sap of stressed plants. The model also predicts that the pH gradient across the cortical plasma membrane has the most distinct effects on redistribution of ABA into the xylem sap of stressed plants and, additionally, that the ABA concentration in the rhizospheric aqueous solution can play an im portant role in root-to-shoot signalling.

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