Abstract: Structural changes in the pollen tubes of the ‘Starking Delicious’apple in vivo was investigated by transmission electron microscope. Itwas found that a slow growth of the pollen tube after 24 h for the self-pollination. Compared with the cross-pollination, there were numerous bipartite particles in the pollen tube cell and some changes in 48 h for the self-pollination, either appeared such as rupture of the pollen tube, release of the cellularmaterials, thickening of the outer walls of some pollen tube cells. At the time without pollination, or 24 h after self- and cross-pollination, in the samp les that pollen tubes did not exist, the S-RNase was localized in the stylar transmitting tissue cells. However, in 48 h after pollination with self- or cross-pollen, in the samp les that pollen tubes existed, the S-RNase was observated in the intercellular space or into pollen tubes.

Key words: Apple, Self-pollination, Pollen tube, Structural change, S-RNase, Localization