ANAEROBIC ACCUMULATION OF 4-AMINOBUTYRATE IN RICE SEEDLINGS - CAUSES AND SIGNIFICANCE

Accumulation of 4-aminobutyrate is induced by anoxia in rice seedlings. The induction of 4-aminobutyrate accumulation in aerobic conditions by treatments with exogenous 4-aminobutyrate, Gabaculine and glutamate is well tolerated by the seedlings. The inhibition of protein synthesis in aerobic and anaerobic conditions by cycloheximide shows that this process competes with glutamate decarboxylase for glutamic acid. The sensitivity of the anaerobic 4-aminobutyrate accumulation to azaserine indicates that glutamate synthase is important in maintaining glutamate availability. The different tolerance to anoxia and protein metabolism of shoot and root of rice suggests that the causes leading to 4-aminobutyrate accumulation in these tissues are different. It is suggested that ammonia reassimilation in root plays an important role in the synthesis of 4-aminobutyrate.