Changes of H+pumps of tonoplast vesicle from wheat rootsin vivoandin vitrounder aluminum treatment and effect of calcium

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Abstract
Wheat seedlings were treated with 0.1 mM Al for 7 days. Tonoplast vesicles were isolated from apical segments of roots and activities of H+‐ATPase and H+‐PPase measured. Compared with the control, 0.1 mM Al increased H+‐ATPase activity and decreased H+‐PPase activity. High external supply of calcium (Ca) (5 mM) diminished the extent of the stimulation of H+‐ATPase activity and alleviated the reduction of H+‐PPase activity under Al treatment. However, 0.1 mM Al treatment in vitro resulted in the inhibition of H+‐ATPase activity with the decrease of Vmax and Km for ATP. In vitro treatment with 0.1 mM Al also decreased the H+‐PPase activity, but increased the Km for PPi.