Abstract
S-adenosylmethionine (SAM) synthesized from methionine serves as a common substrate for the biosynthesis of ethylene and polyamine. To clarify the relationship of ethylene and polyamine metabolism during senescence of Hibiscus syriacus L. flowers, ethylene production and changes in the contents of ACC, ACC-conjugate, and polyamines in the petal were examined. Ethylene production greatly increased just around the beginning of petal in-rolling and paralleled an increase of ACC-conjugate in the petal. Spermine decreased with the petal senescence in contrast to the sharp rise in ethylene production. AVG, which inhibits ACC synthesis from SAM, extended the flower longevity and maintained a high spermine content in the petal. In contrast, MGBG, which inhibits SAM decarboxylation, promoted ethylene production and shortened the flower longevity. These results suggest that a competition for SAM between ethylene and polyamine biosynthesis plays a key role in determining the flower longevity in H. syriacus L.
