Induction of nitrate reductase by chloramphenicol in detached cucumber cotyledons

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Abstract
Chloramphenicol (CAP) induced nitrate reductase activity (NRA) in detached, etiolated cucumber (Cucumis sativus L.) cotyledons. The effect was reduced by cycloheximide. Light was not necessary for induction of the enzyme but potentiated the effect of CAP as an inducer of NRA, despite the fact that the antibiotic inhibited chlorophyll accumulation. CAP at suboptimal concentrations (2.5–5 mM) acted synergistically with succinic acid-2,2-dimethylhydrazide (B-Nine) and benzylaminopurine (BAP) in respect to induction of NRA, the effect being especially marked in darkness. The highest NRA was found in cotyledons treated for 24 h with a mixture of CAP+BAP+B-Nine. The effects of KNO3 and CAP on NRA were neither synergistic nor additive. KNO3 and BAP induced NADH-NR (EC 1.6.6.1). The same was true for CAP and B-Nine, but the latter two compounds induced, in addition, some activity of another NR that could utilize NADPH as an electron donor.