Timetable of Stigmatic Receptivity and Development and Pollen Tube Growth in Chamelaucium uncinatum (Myrtaceae)

Abstract

The stigma of Chamelaucium uncinatum Schauer is small and unreceptive at anthesis, but increases in size and becomes fully receptive 7 days after anthesis. After germination, pollen tubes grow intercellularly through the stigma and transmitting tissue of the style. Chamelaucium uncinatum has a single loculus containing six ovules with axile placentation. The transmitting tissue skews to one side within the ovary and the pollen tubes grow into the placenta via an invagination along one end of the loculus. Pollen tubes are smooth-walled in the transmitting tissue of the style and ovary, but within the loculus pollen tubes produce short side branches. Secondary pollen presentation occurs in C. uncinatum with the stigmatic region being used as a pollen presenter. If the self-pollen is not removed from the stigma prior to the onset of receptivity self-pollination may occur.