Flowering dynamics and dichogamous mechanism in Magnolia grandiflora

Through field investigation, we studied the flowering dynamics, pollen viability, stigma receptivity and dichogamous mechanism of Magnolia grandiflora by bagged artificial pollination, thiazolyl blue(MTT) dyeing, stigma tabletting and other methods. The results showed that: 1) during the five--six days flowering period of an individual flower, two-times opening-closure flowering was observed; 2) Pollen viability decreased over flowering stage, and the optimal pollination period was in the first opening stage when the stigmas were receptive to xenogamous, geitonogamous and self pollinations; 3) After self-pollinating, self-incompatibility did not appear on the stigma surface nor in the styles, and fruits and seeds could be set, indicating that M. grandiflora is self-compatible to some degree; 4) From the perspective of reproduction, we infer that subgenus Yulania is more primitive than subgenus Magnolia; 5) Protogyny in M. grandiflora lies in a mechanism that determines the anther dehiscence stage, thus reducing self-pollination and interference between pollen and stigmas.