Pollination-Induced Ethylene in Carnation (Role of Stylar Ethylene in Corolla Senescence)

In carnation (Dianthus caryophyllus L. cv White Sim) cell to cell communication between the pollen and pistil induces ovary development and corolla senescence. The production of elevated ethylene by the style is the first measurable postpollination response. This is followed by a wave of ethylene production from the other floral organs. To investigate the regulation of ethylene biosynthesis in pollinated flowers we measured ethylene production and the expression of 1-aminocyclopropane-1-carboxylate synthase and 1-aminocyclopropane-1-carboxylate oxidase transcripts in individual floral organs after pollination. Ethylene production by pollinated styles can be defined temporally by three distinct peaks. By pollinating a single style from a multistyle gynoecium, it was determined that the unpollinated style produces ethylene that corresponds to the first and third peaks observed from a pollinated style. Inhibition of ethylene action in the pollinated style by diazocyclopentadiene treatment prevented both pollination-induced corolla senescence and ethylene production from the ovaries and petals. Treatment with diazocyclopentadiene decreased stylar ethylene production during the second peak and completely inhibited the third peak of ethylene in both pollinated and unpollinated styles. This later auto-catalytic ethylene in styles is likely responsible for pollination-induced corolla senescence and ovary development.