Abstract: 【Objectives】Ammonium and nitrate nutrition strongly affect the rhizosphere pH. The response of upland crop to the different pH in root with ammonium and nitrate supplies was studied. 【Methods】 Using a hydroponic experiment, sorghum(Sorghum bicolor)was supplied with NH+4-N or NO-3-N as sole nitrogen nutrition. After 3 weeks' cultivation, the plasma membrane vesicles of sorghum roots were isolated using a two-phase system with poly-glucose. The rhizosphere pH and the plasma membrane H+-ATPase hydrolytic activity were measured, and the enzyme concentration was tested by immune hybridizes.【Results】 The activity of H+-ATPase in the plasma membrane of sorghum roots supplied with NH+4-N(pH3)is 8.81 μmol Pi/(mg·min)and is markedly higher than that supplied with NO-3-N(pH 7)(3.82 μmol Pi/(mg·min). If the pH was adjusted to 7 in the medium with ammonium nutrition, the activity of H+-ATPase is decreased. In contrast, if the pH was adjusted to 3 in the medium with nitrate nutrition, the activity of H+-ATPase is increased, and the activity of H+-ATPase in sorghum roots treated by ammonium nutrition related to the protein concentration. These results indicate that the higher activity of plasma membrane H+-ATPase in sorghum roots is affected by the rhizosphere pH. However, ammonium has stronger influence on the activity of plasma membrane H+-ATPase, even at the same medium pH.【Conclusion】Plasma membrane H+-ATPase could adapt to the rhizosphere acidification by enhancing its activity, either under ammonium or nitrate application. In contrast to the H+ consumption after nitrate reduction, the H+ production after ammonium assimilation should be pumped outside the root cell with further enhancement of the plasma membrane H+-ATPase activity.This might be the mechanism of adaptation to ammonium nutrient by sorghum roots.