Bialaphos, L-2-amino-4-[(hydroxy) (methyl) phosphinoyl]butyryl-L-alanyl-L-alanine, induced a high level of sterility in rice, when applied at a concentration of 0.1 mM at meiosis. Since it was known that bialaphos affected glutamine synthetase (GS), its activity on GS extracted from shoots of the rice plant (Oryza sativa) was examined. Bialaphos did not inhibit GS at a concentration of 0.1-3 mM. However, L-2-amino-4-[(hydroxy) (methyl) phosphinoyl]butyric acid (L-AMPB), a metabolite of bialaphos, completely inhibited GS at a concentration of 1 mM. In sterile anthers produced by bialaphos treatment, a decrease in proline and an increase of aspartic acid and glutamic acid was observed. The decrease in proline in anthers treated with bialaphos was similar to that of cytoplasmic male-sterile anthers in rice.
