Ornithine and arginine decarboxylases and polyamine involvement during in vivo differentiation and in vitro dedifferentiation of Datura innoxia leaf explants

Abstract

The effects of exogenous ornithine, arginine and polyamines added to media leading to root, callus or bud initiation of Datura innoxia Mill. leaf explants growing in vitro were examined. Ornithine and arginine decarboxylase activities (ODC, EC 4.1.1.17; ADC, EC 4.1.1.19) as well as endogenous polyamine levels were also determined during the course of in vivo differentiation of the leaves and their subsequent in vitro dedifferentiation under rooting, callusing, or budding conditions. Decarboxylase activities were determined by measuring the 14CO2 released and the polyamines were quantified after dansylation by thin‐layer chromatography. In vivo, ODC and ADC activities decreased from shoots to young to old leaves. In vitro, synergistic effects between ornithine and indole‐3‐acetic acid on rhizogenesis were detected, while arginine was not effective. Exogenous putrescine also acted synergistically with auxin by promoting root growth. A close relationship was found between rhizogenesis, ODC activity and increase in endogenous putrescine and spermidine levels. ODC increased during the induction and time course of cell dedifferentiation and seemed to support these events, while ADC seemed to support only the later events involving redifferentiation.