To characterize the cytoplasmic structure reorganization during plant meiosis, the male meiocytes of Althaea rosea (L.) Cavan were examined under the combination of light and electron microscopy. Light microscopic observation of the toluidine blue-stained thick resin sections of young anthers revealed that the meiocytes of sporogenous cell stage were extremely voluminous and variable in shape and division plane. The cell walls (CWs) between some meiocytes were discontinuous at one or several site(s). These discontinuous portions varied between 0.2 and 3.0 microm in length. In addition, it was found that some meiocytes were able to produce protuberances that extended into another meiocyte. When transversally sectioned, the protuberance extending to another cell looked like a small cell lying in another cell. Transmission electron microscopy (TEM) showed that there were many long flat ER cisternae that were actively wrapping around a portion of cytoplasm in the male meiocytes at the sporogenous cell stage. During pre-meiosis interphase and early prophase I, a number of huge (0.5-1.0 microm diameter) spherical membrane-bound inclusions (MBIs) lined by single or double layer(s) of membrane were formed, each membrane actually representing one tightly appressed endoplasmic reticulum (ER) cisterna. The MBIs contained many granular, lamellar and fibrillar structures, and even small MBIs. Moreover, it was found that the MBIs could associate with the cytoplasmic channels (CCs) on CWs to release their contents into the cytoplasm of the opposite cell or directly extend from one cell to another through the CC. Taking all the data together, it is suggested that association of the MBIs and other organelles with CCs possibly functions in eliminating the non-identity of cytoplasm of the male meiocytes caused probably by the random asymmetric division observed at sporogenous cell phase, so as to ensure production of a large number of identical functional male gametes required for successful fertilization.

The mechanism of anther abortion in a male sterile (ms) line (Longyou 9S) of Brassica napus L. was evaluated by a combination of light and electron microscopies. Light microscopy showed that the tapetal cells of the ms line appeared smaller than those of its fertile line, sporogenous cells were rich in vacuoles, and pollen mother cells dismantled before the tetrad stage. Electron microscopy demonstrated that sporogenous cells were also rich in very long, plate-shaped endoplasmic reticulum cisternae that actively encircled portions of cytoplasm with organelles. In later stages, many large membrane-bound inclusions were observed in the sporogenous cells. These membrane-bound inclusions were lined by single or multiple layer(s) of the endoplasmic reticulum membranes and contained vacuoles, ribosome, plastid, mitochondria, small membrane-bound inclusion, and/or intact nuclei. In meiotic interphase and early meiosis prophase I, many vesicle aggregations and multivesicular bodies containing numerous vesicles appeared in pollen mother cells. More interestingly, some of the multivesicular bodies lay in deep cytoplasm or near cell wall, and some appeared fused with plasmalemma and released the inner vesicles out of plasmalemma. Such released vesicles gradually dispersed and later disappeared. The observations suggest that active endoplasmic reticulum-dependent autophagic programmed cell death and multivesicular body-dependent polar vesicle trafficking are probably present in the studied male sterile line.