| Abstract: | The four-celled mature pollen of Ginkgo biloba L. just shed from the microsporangia,was round in shape and contained a very large germination area with monosulcate sulcus walled withtwo semicircular and nearly perpendicular parts of exine, and the pollen was coated with a compactirregular striations and spinules in parts other than the germination area. The pollen became boatshaped and was bilaterally symmetrical when it was in air or under cold storage, but rapidly roundedoff in cultural solution. Studies on early morphogenesis of the male gametophyte in vitro and in vivorevealed that the tube nucleus turned a certain degree of angle, and was followed by lateral germination, while the non-active pollen maintained its round shape. The results suggest that the internalfeature of the pollen tube could be a determinant factor contributing to the expression of the characteristic events of lateral germination of the male gametophyte in G. biloba. Furthermore, this biologically consistent character, together with the characteristic pollen morphology, is quite different fromthose of other groups in gymnosperms such as Cycas and Pinus. This might be a critical characterrelevant to the systematic position of G. biloba. |
