Abstract: The previous studies showed that the expression of chloroplast GS2 is mediated by light but cytosolic GS1 and GSin non photosynthetic tissues of higher plants are little influenced.In the current report,we have investigated that GSisozymes in rice roots respond to light using GSactivity staining and Western blotting.Both GSra and GSrb activity and their protein bands were detected at the illumination of sunlight and the incandescent lamp in the controlled environment chamber but GSrb activity and its protein bands were not observed under keeping out direct sunlight with the nylon net.The light intensity after the keeping out sunlight was higher than that of the incandescent lamp.This showed that light intensity was not a crucial factor for influencing GSrb expression.The activity and the protein bands of GSrb in rice roots were observed still in the light/dark transition and the dark seedlings.GSra activity was not remarkably changed at the light treatment.The results suggest that the effect of light on the expression of GSrb isoform in rice roots may be achieved through some unknown factor(s) resulted from the interaction of some spectra.