Ultrastructural Features of Prunus Avium L. Pollen Tube in Vivo

SUMMARYUltrastructural features of the compatible pollen tube of Prunus avium (L.) growing in vivo are described. During its growth the tube has four different zones reflecting a functional specialization. The cytoplasm of the apical or growth zone contains two types of secretory vesicles probably involved in the formation of the tube wall. The sub-apical zone, in addition to the secretory vesicles, shows the presence of dilated rough endoplasmic reticulum (RER) cisterns containing electron-dense material which does not react to the test for polysaccharides. In the nuclear zone the vegetative nucleus and the generative cell can be observed; this zone is followed by the vacuolization and callosic plug formation one.The function of secretory vesicles, as well as other ultrastructural features, are discussed in relation to the self-incompatibility phenomenon.