Ethylene production and post-pollination development in Dendrobium flowers treated with foreign pollen

Dendrobium ‘Pompadour’ flowers fade early following pollination. This is associated with increased ethylene production and early epinasty. These effects are also produced by application of 1-aminocyclopropane-1-carboxylic acid (ACC) on the stigma. Pollen (one anther each) from Ruellia tuberosa L. (Acanthaceae) and Caesalpinia pulcherrima (L.) Sw. (Fabaceae) also increased ethylene production and caused early epinasty and fading. Pollen of Hibiscus schizopetalus (Mast.) Hook.f. (Malvaceae), in contrast, had no effect. R. tuberosa pollen increased ACC concentration and ACC synthase activity of the orchid flowers. Aminooxyacetic acid (AOA) pretreatment prior to R. tuberosa pollination prevented early fading, epinasty and the increase in ethylene production. It also prevented the increase in ACC concentration, and ACC synthase activity. Ovary growth was stimulated by Dendrobium ‘Pompadour’ pollinia, not by any of the incompatible pollen. Applied ACC did not promote ovary growth. It is concluded that incompatible pollen can hasten senescence and epinasty by increasing ACC synthase activity and ethylene production. Ovary growth, in contrast, is apparently not primarily regulated by ethylene.