THE RICE COLEOPTILE - AN EXAMPLE OF ANAEROBIC NITRATE ASSIMILATION

Nitrate present in rice caryopses can be reduced to ammonium and the a mmonium subsequently assimilated by the coleoptile during anaerobic ge rmination. All the enzymes of nitrate reduction and ammonia assimilati on are present in the coleoptile. The supply of (NO3)-N-15 confirms th at the nitrate nitrogen is anaerobically incorporated into amino acids . Under anoxia, nitrate and nitrite reductase activities are increased in the coleoptile by exogenous nitrate. The importance of nitrate uti lization during the anaerobic germination of rice caryopses is discuss ed.