EFFECTS OF INTERACTION BETWEEN POLYAMINES AND BENZYLADENINE ON BETACYANIN SYNTHESIS IN AMARANTHUS SEEDLINGS

The synthesis of betacyanin in Amaranthus cotyledons is a cytokinin dependent process and forms a sensitive bioassay to study interactions between polyamines and cytokinins. Treatment with benzyladenine or diamines (putrescine and diaminopropane) increased the betacyanin content 1.5- to 2.5-fold. In contrast to diamines, spermidine and spermine depressed the synthesis of the pigment. Furthermore, when benzyladenine was applied simultaneously with polyamines, it reinforced the effects of putrescine and counteracted the inhibition due to spermidine and spermine. When seedlings were treated with benzyladenine, the endogenous level of putrescine, spermidine and spermine was raised by 27-36%. The addition of Difluoromethylornithine (DFMO) and Difluoromethylarginine (DFMA) to benzyladenine prevented the rise in betacyanin and polyamine contents. These results seem to favour a participation of polyamines in benzyladenine-dependent betacyanin synthesis but suggest that exogenous spermidine and spermine could have non specific-effects.