Abstract
The main developmental stages of the pollen wall of Magnolia grandiflora were investigated. Microspore tetrads varied in their morphology. In late microspore tetrads during the callose period, pro-columellae condensed around protrusions of the plasmalemma. As a result of the accumulation of sporopollenin precursors on the protrusions of the plasmalemma, columellae became evident. At a late tetrad stage, the foot layer developed on a white-line-centered lamella. At free microspore stages, the units of the exine thickened, and on further development, white-line-centered lamellae appeared over the inner surface of the foot layer. These lamellae represented a transitory or rudimentary endexine. At the vacuolate stage, a characteristic vesicular-fibrillar layer developed under the rudimentary endexine. The intine developed at the young pollen grains stage and differentiated into two zones with different electron density. The possible function of endoplasmic reticulum and Golgi vesicles in the development of the vesicular-fibrillar layer and the intine is discussed.
