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Using modified compartmental analysis the unidirectional fluxesof abscisic acid (ABA) and their cytoplasmic and vacuolar contentsin 3H-ABA preloaded barley root segments (Hordeum distichoncv. Aura) have been studied. When root segments were stressedosmotically with sorbitol (osmotic potential of the media 0= 0.2 MPa) cytoplasmic and vacuolar contents of ABA were enhanced.Under increased stress cytoplasmic and vacuolar contents weremuch lower than in the unstressed controls. ABA fluxes werevery sensitive to osmotic stress and ABA transport from thecytoplasm of the xylem parenchyma to the xylem vessels (cx)was rapidly inhibited. The cultivar Aura has higher cytoplasmicand vacuolar ABA contents than the barley cultivar Kocherperle.This correlates well with the higher stress tolerance of theAura cultivar. Key words: Abscisic acid, Compartmentation, Osmotic stress 相似文献
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An efflux compartmental analysis of abscisic acid (ABA) in barleyroots revealed two compartments of ABA, a fast exchanging one(probably the cytoplasm) containing 3.63 µM ABA and aslowly exchanging compartment (probably the vacuoles) whichcontained 0.39 µM ABA. 相似文献
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Vacuolar Na/K Exchange, its Occurrence in Root Cells of Hordeum, Atriplex and Zea and its Significance for K/Na Discrimination in Roots 总被引:1,自引:0,他引:1
JESCHKE WOLF DIETER; STELTER WILFRIED; REISING BERND; BEHL RUDOLF 《Journal of experimental botany》1983,34(8):964-979
Using excised low-salt roots of barley and Atriplex hortenslsthe transport of endogenous potassium through the xylem vesselswas studied It was enhanced by nitrate and additionally by sodiumions which apparently replaced vacuolar potassium which wasthen available in the symplasm of root cells for transport tothe shoot Vacuolar Na/K exchange also has been investigatedby measurements of longitudinal ion profiles in single rootsof both species. In Atriplex roots a change in the externalsolution from K+ to Na+ induced an exchange of vacuolar K+ forNa+, in particular in the subapical root tissues and led toincreased K+ transport and loss of K+ from the cortex. In inverseexperiments a change from Na+ to K+ did not induce an exchangeof vacuolar Na+; merely in meristematic tissues Na+apparentlyfrom the cytoplasmwas extruded in exchange for K+. Inroots of barley seedlings without caryopsis, as in excised roots,a massive exchange of K+ for Na+ was observed in the continuouspresence of external 1.0 mM Na and 0.2 mM K. This exchange alsowas attributed to the vacuole and was most pronounced in theyoung subapical tissues. It did not occur, however, in the correspondingtissues in roots of fully intact barley seedlings. In these,the young tissues retained a relatively high K/Na ratio alsoin their vacuoles. Similarly, contrasting results were obtainedwith intact and excised roots of Zea mays L. Based on theseresults a scheme of the events that lead to selective cationuptake in intact barley roots is proposed. In this scheme acrucial factor of selectivity is sufficient phloem recirculationof K+ by the aid of which K+ rich cortical cells are formednear the root tip. When matured these cells are suggested tomaintain a high cytoplasmic K/Na ratio due to K+ dependent sodiumextrusion at the plasmalemma and due to recovery of vacuolarK+ by Na/K exchange across the tonoplast. Key words: Potassium/Sodium selectivity, Vacuolar exchange, Xylem transport, Hordeum, Zea, Atriplex 相似文献
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Potassium Fluxes in Excised Barley Roots 总被引:4,自引:2,他引:2
The method of the modified compartmental analysis for excisedroots has been adopted for measuring K+-fluxes and compartmentationin barley (Hordeum distichon) roots. Efflux of 42K and 86Rbindicated that more than two intracellular compartments wereinvolved in the tracer exchange; the 42K data clearly showedthe components. On the basis of the efflux behaviour of theapical and more basal tissues of the roots, the three componentsof efflux were attributed to the cytoplasm of differentiated(fast) and meristematic tissues (intermediate) and to the vacuoles(slow exchange) of the roots. A model is proposed on the basisof which, the fluxes corresponding to the meristematic and differentiatedtissues of the root can be estimated. Additionally, fluxes ofthe differentiated root tissues were determined by using effluxdata obtained with root segments without apical tissues. Thedata obtained in both ways compare reasonably well and agreeto independent chemical measurements. Comparison of the 42K and 86Rb efflux data show strong discriminationof K in favour of Rb+ and indicate that 86Rb is not suitableas a tracer for K+ in efflux measurements, at least with barleyroots. 相似文献
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