Effect of a cytokinin antagonist on cytokinin and light-dependent amaranthin synthesis inAmaranthus Tricolor seedlings

InAmaranthus tricolor seedlings, amaranthin synthesis can be induced under the effect either of a cytokinin or of white light. The 3-methyl-7-(n-pentylamino)pyrazolo(4,3-d)pyrimidine (PAMPP), a cytokinin analog that strongly inhibits the growth of tobacco callus, antagonizes the stimulating effect of cytokinin as well as stimulation by light. In dose-response terms, the inhibitory effect of PAMPP was described as competitive with respect to N⁶-benzyladenine (b⁶Ade) or light. The inhibition by PAMPP of the b⁶Ade amaranthin test response or the inhibition by this cytokinin analog of the light amaranthin test response were both reversed by either subsequent light or b⁶Ade treatment.