Extrusion of protons as a response to high-NaCl stress in intact mung bean roots was investigated at different external concentrations of Ca2+ ions ([Ca2+]ex). The extrusion of protons was gradually enhanced in the roots exposed to 100 mM NaCl, and high [Ca2+]ex diminished this enhancement of the extrusion. Vesicles of plasmalemma and tonoplast were prepared from the roots and the H+-translocating ATPase (H+-ATPase) activities associated with the two types of membrane and the H+-pyrophosphatase (H+-PPase) activity of the tonoplast were assayed. The plasmalemma ATPase was stimulated in parallel with dramatic increases in the intracellular concentration of Na+([Na+]in). High [Ca2+]ex prevented the increase in [Na+]in and diminished the stimulation of ATPase activity. The tonoplast ATPase showed a rapid response to salt stress and was similarly stimulated even at high [Ca2+]M. The activities of both ATPases were, however, insensitive to concentrations of Na+ ions up to 100 HIM. By contrast, H+-PPase activity of the tonoplast was severely inhibited with increasing [Na+]in under salt stress and recovered with high [Ca2+]ex. These findings suggest that high-NaCl stress increases the intracellular concentration of Na+ ions in mung bean roots, which inhibits the tonoplast H+-PPase, and the activity of the plasmalemma H+-ATPase is thereby stimulated and regulates the cytoplasmic pH.
|ジャーナル||Plant and Cell Physiology|
|出版ステータス||Published - 1992 3月|
ASJC Scopus subject areas