Early biochemical events during cytokinin action inCucumis sativus cotyledons in culture

Abstract

An early event in the temporal sequence of molecular processes that occur during cytokinin and/or K⁺- induced growth and differentiation of etiolated cotyledons ofCucumis sativus L. var. Guntur in culture, was an enhanced specific permeability, resulting in increased uptake of³²P0₄ ³− and 2-deoxy-[³H]-D-glucose. Concomitant increases were also noticed in RNA synthesis followed by enhanced elaboration of protein, DNA and chlorophyll in that order. However, the cytokinins (benzyladenine or benzyladenosine) did not increase cyclic AMP concentrations or the preferential synthesis of poly(A)-rich RNA. K⁺ augmented [³H]-benzyladenine uptake thereby explaining the synergistic action of the two growth promoters. [³H]-Benzyladenine was metabolized in this tissue presumably to benzyladenosine and benzyladenosine monophosphate, It is suggested that the early alteration in the permeability of the tissue induced by cytokinin and/or K⁺ results in a greater mobilization and utilization of the stored products in the cotyledon culminating in growth and differentiation into a leaf-like structure.