The effect of benzyladenine (BA) on the total chlorophyll content and on endogenous paramagnetic Mn2+ was studied in excised cucumber cotyledons. BA stimulates the release of Mn from its native bound or complexed state which is evident from a higher amplitude of the Mn2+ sextet. Enhancement in the amplitude of Mn2+ sextet may be taken as a parameter for the release of cations from storage bodies. Application of bivalent cations stimulates chlorophyll content under conditions where the concentration of available endogenous cations, measured by the amplitude of Mn2+ sextet, is low. The stimulation of chlorophyll synthesis appears to be mediated by endogenous cations released under the influence of BA.