Abstract: A fluorescence microscope was used to observe number of pollens adhered on stigmas of wild Magnolia officinalis under natural conditions, pollen adhesion to stigmas through self-pollination and geitonogamous pollination, pollen germination and the growth of pollen tubes. It was found that under natural pollination conditions, only 12% of stigmas had some pollen grains adhered, and the number of pollens adhered on each stigma was rather limited; Self-pollination increased the number of pollens adhered on stigmas but the pollens were futile and could not germinate; however, geitonogamous pollination also increased the number of pollens adhered on stigmas and, moreover, the pollens could germinate, but later in time. After pollens got in contact with stigmas, pollen tubes began to grow and 4 hours later, most pollen tubes stopped extending with tips bulging and even twisted. Along with the growth of tubes, a series of callose reactions were observed. Calloses were found at the contacts between the stigmas and pollen tubes and on the surface of stigma papillose cells. They hindered normal extension of pollen tubes. Therefore, the lack of pollination insects and the existence of the pre-fertilization obstacle are the two principal causes leading to endangeredness of the wild M. officinalis.

Key words: Magnolia officinalis, pollen, stigma, fluorescence microscope