Abstract: By means of fluorescence microscopic technique, whole stain-clearing technique, and paraffin sectioning procedure, the fertilization compatibility of Catalpa bungei after self, intraspecific and interspecific cross-pollination were examined. It was founded that pollens could germinate whether self pollination or intraspecific and interspecific pollination. But both the germination time and germination rate was significantly different. The pollen tubes either grew in the secretions of stigmas or penetrated the papilla cells, and then went along the inner vascular bundle, finally grew into the styles along the intercellular space of transmitting tissues. Most pollen tubes grew quickly to the basement of the style at 12 to 24 hours after intraspecific and interspecific pollination, and entered the ovary after 1 or 2 days entered the ovary. Double fertilization was observed about 96 to120 hours after cross-pollination. At the same time we saw with naked eyes that the ovaries turned red and swelling. After self-pollination, 36% of pollen tubes ceased on the stigma or in the upper styles. 42% of pollen tubes could grow into the ovaries at 72 to 96 hours after self-pollination. Double fertilization could not be observed although part of pollen tubes penetrated the ovules. Pistils fell off at 120 hours after self-pollination without presenting any swelling of the ovary. It was clear that C. bungei exhibited self-incompatibility, intraspecific cross-compatibility, and interspecific cross-compatibility. Because the site of pollen tube termination was in the ovary, and the time was pre-zygotic, C. bungei was considered to be a pre-zygotic late-acting self-incompatibility type.

Key words: Catalpa bungei, pollen germination, pollen tube growth, late-acting self-incompatibility