REQUIREMENT FOR A LONG LAG PERIOD FOR THE INDUCTION OF NITRATE REDUCTASE IN WHEAT (TRITICUM-AESTIVUM) EMBRYOS DURING GERMINATION

The induction of nitrate reductase (NR) in the embryos of wheat required a period of 20 h of incubation in nitrate during the early stages of seed germination. The lag phase in the development of NR activity was not due to the non-availability of nitrate in the embryos, the presence of a nitrate reductase inactivating factor, or the synthesis of inactive NR. At the onset of the inducible phase the enzyme was synthesized de novo, but was not dependent on the synthesis of fresh mRNA. Protein synthesis during the lag phase was essential for the subsequent induction of NR in the inducible phase.