Figure 3.

Effect of Al concentration on the secretion (A) of citrate and the activity (B) of plasma membrane H⁺-ATPase in Arabidopsis roots. Arabidopsis seedlings were incubated in one-sixth Murashige and Skoog solution for 14 d, then exposed to 15 or 30 μm Al (9.1 μm Al³⁺ activity) in one-sixth Murashige and Skoog solution (pH 4.5) for 2 h. After treatment, the incubation solution was analyzed for citrate by an enzymatic method. The whole roots of Arabidopsis were analyzed for the activity of plasma membrane H⁺-ATPase. See details in “Materials and Methods.” Each value is the mean ± se (n = 5). Different letters in the same column or plant indicate that the values are significantly different at the 0.05 level, according to Duncan's Multiple Range Test.