Ethylene production, senescence and ethylene sensitivity of Dendrobium 'Pompadour' flowers following pollination

Dendrobium 'Pompadour' flowers had a burst of ethylene production that peaked 9 h after pollination. Pollination increased 1-aminocyclopropane-1-carboxylic acid (ACC) content and ACC synthase activity. Ovary, lip and pedicel ACC levels and ACC synthase activity were many-fold greater than those of the petals and sepals following pollination. Aminooxyacetic acid (AOA) application to the stigma prior to pollination reduced ethylene production, ACC levels and ACC synthase activity. Ethylene production by pollinated orchid flowers, with ACC application, increased more rapidly than in nonpollinated orchid flowers with ACC application. Pollination induced a rise in ethylene production, and then premature senescence. The first sign of premature senescence was a downward curvature of orchid flowers accompanied by drooping of the petals and sepals. Both AOA and 2,5-norbornadiene (NBD) delayed premature senescence of pollinated orchid flowers, though AOA was the more effective. Exogenous ethylene induced premature senescence of orchid flowers similar to pollination and pollination increased the ethylene-sensitivity. AOA treatment did not alter ethylene sensitivity of pollinated orchid flowers.