Intracellular pH and Proton-Transport in Barley Root Cells under Salt Stress: in Vivo 31P-NMR Study |
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Authors: | Katsuhara Maki; Yazaki Yoshiaki; Sakano Katsuhiro; Kawasaki Toshio |
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Institution: | 1 Research Institute for Bioresources, Okayama University Kurashiki, 710 Japan
2 Department of Plant Physiology, National Institute of Agrobiological Resources Tsukuba, 305 Japan |
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Abstract: | Salt stress-induced changes of intracellular pH and in levelsof phosphorous compounds were monitored in intact root tipsof barley seedlings (Hordeum vulgare cv. Akashin-riki) by invivo 31P-nuclear magnetic resonance (NMR) spectroscopy. Vacuolaralkalization was observed after treatment with both 300 and500 mM NaCl. Much of the observed apparent alkalization of thecytoplasm was eliminated when the effect of Na+ ions on thetitration curve was considered. Within 1 h after the initiationof salt stress, levels of glucose-6-phosphate and UDP-glucosedecreased markedly, and such decreases might lead directly orindirectly to cell death. Simultaneous measurements of the externaland intracellular pH revealed the promotion of external acidificationand internal alkalization during salt stress. Possible mechanismsof Na+/H+ antiport at the tonoplast and the role of proton-pumpin the plasma membrane are discussed.
3Present address: Shijonawate Gakuen Women's Junior College,Daito, Osaka, 574 Japan. |
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