RESUMEN
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. The phosphorus uptake rates of tomato seedlings under phosphorus starvation significantly increased and were much higher than those of controls and reached maximum values under the starvation for 7 days. The tonoplast H(+)-ATPase activity in the roots of tomato seedlings increased under phosphorus starvation and reached maximum values under the starvation for 7 days, while the activity of the control changed little. Kinetic analysis of tonoplast H(+)-ATPase showed that phosphorus starvation significantly lowered the K(m) value, but had no significant effect on the V(max) value of the enzyme. 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.