Inhibition of nitrate reductase induction in germinating barley embryos by endosperm

Abstract

A lag phase of 24 h has been found in the induction of nitrate reductase (NR) in barley seeds. This lag phase was eliminated if the embryos were detached from the endosperm and incubated in nitrate. In detached embryos the NR activity was detected as early as 4 h of germination, and maximum activity was observed at 12 h. Induction of NR in detached embryos was not affected by actinomycin D, inhibited by 67% in the presence of cordycepin and completely inhibited by cycloheximide. Endosperm exudate inhibited the induction of NR in detached embryos. Nitrate accumulation was found to be same in attached and detached embryos and accumulation was not affected by the inhibitors. The study suggests that an endogenous factor is present which inhibits the induction of NR during the first 24 h of germination in intact barley seeds.