Studies on the Microsporogenesis and Development of the Male Gametophyte of Magnolia championii Benth.

The microsporogenesis and the male gametophyte development of Magnolia championii Benth.were investigated.The general course of the pollen formation in Magnolia championii agrees with that in other plants of Magnoliaceae.Its anther is four sporangia.The archesporial cell is hypodermal in origin.The wall of an anther consists of the epidermis,two endotheciums,two ephemeral middle layers,and one or two tapetum layers.The tapetum is glandular and is of one to three nucleates.The division of the microsporocyte is of the modified simultaneous type.The microspore tetrads are tetrahedral or isobilateral,rarely decussate.The pollen grains are 1-sulcate and shed at the 2-celled stage.The low pollen germination rate results from various abortions at different stages in development,such as secondary sporogenous cell,microspore mother cell and tetrads.Of all the abortions observed the most common is that the microspores stopped developing and were sheded off from the anthers in a uninucleate condition.For this occurrence the failure of timely transfer of nutrition from the connection to the anther wall is believed to be responsible.As the environment seems to affect pollen germination rates,it can be speculated that the appropriate air humidity is one of the most important conditions for the regular development of pollen.The sharply changing weather becomes,as it seems,the main reason for the declining population reproduction.