Pre-treatment of rice roots for 2 h in aerobic conditions with two phospholipase C (PLC) antagonists, neomycin and compound 48/80 (C48/80), inhibited accumulation of gamma-aminobutyric acid and increased the loss of K+ in the medium during 3 h of anoxia. The presence of Ca2+ and A23187 (Ca2+ ionophore) nullified the effect of PLC inhibitors. Pre-treatment of rice roots with neomycin and C48/80 abolished the anaerobic increase in the concentration of the PLC product inositol 1,4,5-triphosphate. Stimulation of the anaerobic signal transduction pathway with aluminium fluoride (G protein activator) was attenuated by PLC inhibitors. These findings are consistent with the participation of PLC in the anaerobic response.