Compatible and incompatible pollination and the senescence and ovary growth of Dendrobium flowers

The pollinia from five cultivars of Dendrobium (‘Miss Teen’, ‘Karen’, ‘Sakura’, ‘Willie’, and ‘Pompadour’) were placed on the stigma of open flowers of Dendrobium ‘Miss Teen’ (or ‘Kenny’). The ethylene production and post-pollination development of cross-pollinated flowers were monitored. The pollinated flowers showed two different development patterns depending upon pollination compatibility. The first group, which was pollinated with incompatible pollen from flowers of ‘Karen’ and ‘Miss Teen’, did not exhibit post-pollination symptoms and ovary growth. The second group, which was pollinated with compatible pollen from flowers of ‘Pompadour’, ‘Sakura’ and ‘Willie’, showed premature perianth senescence and induced ovary growth within a day. Compatible pollination of ‘Miss Teen’ flowers resulted in an immediate burst in the production of ethylene and a rapid ovary growth followed by an increase in pollen tube length. In contrast, when ‘Miss Teen’ flowers were self-pollinated or pollinated with ‘Karen’ pollinia, these changes did not occur. In the pollinia of ‘Pompadour’, ‘Sakura’ and ‘Willie’ there were higher levels of auxin and 1-aminocyclopropane-1-carboxylic acicd (ACC) than in those of ‘Miss Teen’ and ‘Karen’. Compatible pollination also resulted in higher ACC synthase and ACC oxidase activities within 12 h after pollination than after pollination with incompatible pollen. There was a low level of ACC oxidase activity in non-pollinated flowers and a higher ACC oxidase activity in the column plus pedicel than petal plus sepal and lip.