磷饥饿下番茄幼苗根系液泡膜H+-ATPase活性的适应性变化

以‘世纪星’番茄为材料。研究了磷饥饿下番茄幼苗的生长状况及其根部液泡膜H^＋-ATPase活性的适应性变化。结果表明：磷饥饿下番茄幼苗的平均高度均低于对照苗，而主根长度均显著长于对照。磷饥饿提高了番茄幼苗根部液泡膜H^＋-ATPase的水解活性，随着磷胁迫时间的延长，该酶的活性逐渐增大，在磷饥饿7d时达到最大，后又略有降低；而对照番茄幼苗根部该酶的活性变化很小。动力学分析表明：磷饥饿使番茄幼苗根部液泡膜H^＋-ATPase的Km值明显降低，但对该酶的Kmax影响不大。这说明磷饥饿提高了该酶对其底物的亲和力。此外，磷饥饿并不改变液泡膜H^＋-ATPase酶的最适pH值（仍为7．5）。

Adaptive Changes in Activity of Tonoplast H+-ATPase from the Roots of Tomato Seedlings under Phosphorus Starvation

We studied the growth state of tomato seedlings and the adaptive changes in activity of tonoplast H+-ATPase on different days (5 d,7 d,9 d,11 d,13 d) sampling from the roots of tomato seedlings under phosphorus starvation. The results indicated that the average height of the seedlings decreased under phosphorus starvation,while the main roots of the seedlings were significantly longer than those of the control (Figs.1,2). The phosphorus uptake rates of tomato seedlings un-der phosphorus starvation significantly increased and were much higher than those of controls (Fig. 3) and reached maximum values under the starva-tion for 7 days. The tonoplast H+-ATPase activity in the roots of tomato seedlings increased under phosphorus starvation and reached maximum val-ues under the starvation for 7 days,while the ac-tivity of the control changed little (Fig.4). Kinetic analysis of tonoplast H+-ATPase showed that phos-phorus starvation significantly lowered the Km value,but had no significant effect on the Vmax value of the enzyme (Fig.5). The results showed that phosphorus starvation increased the affinity of the enzyme to its substrate. In addition,phosphorus starvation did not alter the optimum pH (7.5) of the ATPase activity (Fig.6).