Aluminum‐dependent dynamics of ion transport in Arabidopsis: specificity of low pH and aluminum responses |
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Authors: | Jayakumar Bose Olga Babourina Sergey Shabala Zed Rengel |
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Institution: | 1. School of Earth and Environment, The University of Western Australia, Crawley WA 6009, Australia;2. School of Agricultural Science, University of Tasmania, Hobart TAS 7001, Australia |
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Abstract: | Low‐pH and Al3+ stresses are the major causes of poor plant growth in acidic soils. However, there is still a poor understanding of plant responses to low‐pH and Al3+ toxicity. Low‐pH or combined low‐pH and Al3+ stress was imposed in order to measure rhizosphere pH, ion fluxes, plasma membrane potential and intracellular H+ concentration in distal elongation and mature zones (MZs) along the longitudinal axis of Arabidopsis thaliana roots. Low‐pH stress facilitated H+ influx into root tissues and caused cytoplasmic acidification; by contrast, combined low‐pH/Al3+ treatment either decreased H+ influx in the distal elongation zone (DEZ) or induced H+ efflux in the MZ, leading to cytoplasmic alkalinization in both zones. Low‐pH stress induced an increase in rhizosphere pH in the DEZ, whereas combined low‐pH/Al3+ stress resulted in lower rhizosphere pH in both root zones compared with the low‐pH treatment alone. Low‐pH stress facilitated K+ efflux; the presence of Al3+ diminished K+ efflux or favored K+ influx into root tissues. In both zones, low‐pH treatment induced plasma membrane (PM) depolarization, which was significantly diminished (P≤ 0.05) when combined stresses (low‐pH/100 µM Al3+) were imposed. After 60 min of exposure, low pH caused PM depolarization, whereas low pH/100 µM Al3+ caused PM hyperpolarization. Thus, low pH and Al3+ toxicity differentially affect root tissues and, consequently, the rhizosphere, which might underpin the differential mechanisms of plant adaptation to these abiotic stresses. |
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