Abstract: In a growth chamber experiment, the response of two rice varieties (Piaui and IAC-47) to nitrate suppression (24 h) and pulses (72 h) was studied. Nitrate suppression in nutrient solution increased plasma membrane H+-ATPase activity in Piaui plants previously grown under 0.5 mM and IAC-47 under 5.0 mM NO3-N. Under NO3- pulses, IAC-47 presented highest H+-ATPase activity in its plasma membrane, while Piaui showed increases in tonoplast V-H+-ATPase activity. These results suggested that under nitrate pulses IAC-47 increased its ability to take up NO3- from nutrient solution. Piaui plants preferentially retrieves nitrate stored from the vacuoles. Plasmalem protein content in Piaui tonoplast was enhanced particularly in -N plants previously grown under 5.0 mM NO3--N. We suggest that these enzymes (H+-ATPases) could be monitored as markers in nitrogen use efficiency study in rice plants.