Style-controlled wilting of the flower.

Differences in rate of wilting in cross-, self-and unpollinated flowers of self-incompatiblePetunia hybrida L. clone W166H appeared to be significant. Wilting rate was fastest following cross-pollination and slowest in unpollinated flowers. The difference between wilting behaviour of cross- and self-pollinated flowers was not caused by rate of pollen tube growth and not by the incompatibility (recognition or rejection) reaction either. It is assumed, that, following pollination, the wilting reaction is only retarded after penetration of pollen tubes of the same genetic composition as the style (complete self-pollination). The number of viable pollen grains necessary to initiate a maximal wilting-rate of flowers following cross- and self-pollination is about 800, which means that a fifth of the stigmatic surface must be covered with living pollen grains. It is suggested that pollen tube penetration and injury of the style have a similar influence on the initiation of wilting.Wilting-rate following pollination is faster in young plants as compared with wilting in old plants. The wilting process of unpollinated and self-pollinated flowers started in the early morning and lasted till afternoon. Cross-pollinated flowers wilted independently of the hour of the day. The role of flower-wilting as a means of communication to the environment with regard to pollination of the style is discussed.