Ethylene in the control of reproductive organ abscission: The model of yellow lupine inflorescence

Ethylene evolution and the contents of 1-aminocyclopropane-1-carboxylic aci d (ACC), ACC synthase, and mRNA for ACC synthase were studied in flower who rls Liable to abscission and those remaining in the inflorescence of lupine (Lupinus luteus L.). The effects of the ethylene-releasing compounds Ethre l and Kamposan as well as inhibitors of ethylene biosynthesis were also inv estigated. The inhibitors of ethylene biosynthesis depressed and ethylene p roducers enhanced flower abscission, but neither changed abscission in the lowest whorl. Ethylene evolution from different whorls and the correspondin g levels of ACC did not correlate with the degree of flower abscission. An increase in ethylene production during flowering was correlated with the ac cumulation of mRNA for ACC synthase. By suppressing flower abscission, the inhibitors of ethylene formation improved seed production, which might be o f practical significance. It is supposed that ethylene not only triggers th e abscission process but also controls the extent of lupine flower abscissi on under variable environmental conditions.