Abstract: The H+-ATPase activity and its H+-pumping capacity of plasmalemma isolated from a conventional Japonica rice (Wuyujing 3), a conventional Indica rice (Yangdao 6), and an upland rice (Brazil upland rice), were measured, respectively. Combined with the results of nitrate uptake kinetic and effects of ammonium on nitrate uptake of 3 varieties, the relationships between parameters was studied. The results show that the H+-ATPase activities of 3 varieties are in consistent with H+-pumping capacity. The H+-ATPase activities and H+-pumping capacities were in the following order: Brazil upland rice > Wuyujing 3 > Yangdao 6. For nitrate uptake the Vmax of Brazil upland rice was significantly higher than those of other genotypes, and was less affected by ammonium. Ammonium has the largest repressive effect on the nitrate uptake by Wuyujing 3 than on that of other 2 varieties. The effect of ammonium on nitrate uptake may be due to the decreasing membrane potential, which could descend the so-called proton-driving-force, and repressing synthesis of nitrate-carrier in plasmalemma. However, ammonium has no effect on the affinity of carrier to nitrate.

Key words: Wetland rice, Upland rice, Genotype, H+-ATPase, H+-pumping, Nitrogen uptake, Root cell membrane