Effect of K+ and H+ stress and role of Ca2+ in the regulation of intracellular K+ concentration in mung bean roots |
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Authors: | Keiichi Torimitsu Makoto Hayashi Eiji Ohta Makotu Sakata |
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Affiliation: | Dept of Instrumentation Engineering, Faculty of Science and Techonology, Keio Univ., 3-14-1, Hiyoshi. Kohoku-ku. Yokohama, Kanagawa 223, Japan. |
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Abstract: | The effects of external K+, H+ and Ca2+ concentrations on the intracellular K+ concentration, [K+]i, and the K+-ATPase activity in 2-day-old mung bean roots [ Vigna mungo (L.) Hepper] were investigated. [K+]i, in mung bean roots was markedly decreased by external K+ or H+ stress and did not recover the initial value even after the stress was removed. This decrease in [K+]i, gradually disappeared with the addition of (Ca2+. Ca2+ may offset the harmful effects of ion stress. Ca2+ seems to have two effects on K+ transport; control of K+ permeability and activation of K+ uptake, although K+-ATPase activity was inhibited by Ca2+ concentrations higher than 10–4 M. We suggest that Ca2+ activates K+ uptake indirectly through the acidification of the cytoplasm. |
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Keywords: | Intracellular pH, ion stress. K+-ATPase 31P-NMR Vigna inungo |
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