The effects of the phytohormones gibberellin (GA.), cytokinin (BA) and abscisic acid (ABA) on ethylene biosynthesis were studied in a model system of spinach leaf discs. All three hormones were found to accelerate ethylene production. The GA3. and BA-enhanced ethylene production during 2 days of incubation resulted mainly from increased ACC synthesis and its conversion to ethylene, as well as from suppression of ACC malonylation. On the other hand, application of ABA, although causing enhancement of both ACC synthesis and ethylene formation from ACC, resulted in a remarkable stimulation of ACC malonylation. The hormones effects were found both on endogenous and on ACC-dependent ethylene production. Further investigation of the stimulatory effect of ABA on EFE activity revealed that it is CO2-mediated. The significance of these hormonal effects on ethylene production will be discussed.
Advances in Agricultural Biotechnology, vol. 26
