Benzyladenine-induced Chlorophyll Formation in Etiolated Cucumber Cotyledons: Differential Responses of δ-aminolevulinic Acid Formation to Inhibitors of RNA ano Protein Synthesis in Darkness and then after Illumination

Abstract

Summary The effect of benzyladenine (BA), applied alone or in combination with inhibitors of RNA and protein synthesis, on growth, chlorophyll and δ-aminolevulinic acid (ALA) accumulation in cucumber ( Cucumis sativus L.) cotyledons in darkness and then after illumination was studied. BA increased the rate of ALA accumulation in levulinic acid-treated etiolated cucumber cotyledons after 2–4 h in darkness. The results when inhibitors of RNA and protein synthesis were present suggested that BA in darkness leads to an acitivation of m-RNA that may already be present, but does not enhance the synthesis of new m-RNA. Moreover, BA stimulated ALA accumulation after illumination. This accumulation is more rapid than observed in the darkness in both controls and BA-treated cotyledons. In contrast to the results in the dark, the result when inhibitors of RNA and protein synthesis were present after illumination suggests that ALA accumulation and chlorophyll synthesis lead to an enhanced synthesis of m-RNA in the nucleus, and not activation of m-RNA with or without BA.