2007 Volume 6 Issue 3 Pages 471-477
In the higher plants, 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 the anthesis and senescence of Hibiscus syriacus L. flowers, ethylene production and changes in the concentration of 1-aminocyclopropane-1-carboxylic acid (ACC), ACC-conjugate, and polyamines in the petal were examined. A very low level of ACC was detected in the petal, and a very low ethylene evolution was observed, even before flower opening. Ethylene production greatly increased just around the beginning of petal in-rolling and paralleled an increase of ACC-conjugate in the petal. With regard to polyamine concentration, spermine decreased with petal senescence in contrast to the sharp rise in ethylene production. Aminoethoxyvinylglycine, which is a potent inhibitor of ACC synthesis from SAM and thereby represses ethylene formation, extended the flower longevity and maintained a high spermine concentration in the petal. In contrast, methylglyoxal-bis (guanylhydrazone), which is a potent inhibitor of SAM decarboxylation and also inhibits spermine biosynthesis, promoted ethylene production and shortened the flower longevity. These findings suggest that a competition for SAM between ethylene and polyamine biosynthesis may play a key role in determining flower longevity in H. syriacus L.
