磷酸饥饿时番茄幼苗酸性磷酸酶活性的变化与Pi吸收的关系

磷酸饥饿时，番茄幼苗根部及地上部酸性磷酸酶活性均显著增强，根部细胞表面酸性磷酸酶及根部外泌的酸性磷酸酶活性亦明显提高。动力学分析表明，磷酸饥饿提高了番茄幼苗根部的酸性磷酸酶对其底物的亲和力。另外，磷酸饥饿对番茄幼苗根部酸性磷酸酶活性的最适ｐＨ值没有影响。钼酸对番茄幼苗根部酸性磷酸酶活性有强烈的抑制作用，对番茄幼苗Ｐｉ吸收速率也有十分明显的抑制效果。以上结果表明，磷酸饥饿时，番茄幼苗Ｐｉ吸收的适应性变化可能与根部酸性磷酸酶特别是根部细胞表面酸性磷酸酶及其外泌酸性磷酸酶的参与密切关联。

Relationship between the Changes of Acid Phosphatase Activities and Pi-uptake of Tomato Seedlings during Phosphate Starvation

The acid phosphatase activities from roots and both stems and leaves of tomato seedlings all increased markedly under phosphate starvation. Phosphate starvation also increased the activities of acid phosphatase from cell surface of, and released by roots of tomato seedlings. The kinetic analysis of acid phosphatase of roots of tomato seedlings revealed that phosphate starvation increased the affinity of the enzyme to its substrate. The results also revealed that phosphate starvation had no effect on the optimum pH (pH 4 93) of the acid phosphatase of roots of tomato seedlings. It was also found that molybdate strongly inhibited not only the activities of acid phosphatase but also Pi-uptake rates of tomato seedlings. All the results indicated that the adaptive changes of Pi-uptake of tomato seedlings during phosphate starvation may closely associate with the changes of the activities of acid phosphatase of the roots, especially those from cell surface of, and released by the roots of the seedlings.