Scanning electron microscopy of the callose wall and intermeiocyte connections in angiosperms

摘要

Scanning electron microscope studies of anthers of the dicotyledonsHelianthus annuus, Solanum tuberosum, andLupinus polyphyllus, and the monocotyledonsIris pseudo-acorisand aLiliumhybrid revealed discontinuities or holes in the meiocyte callose wall and continuity of the plasma membranes of adjacent meiocytes. The holes in the callose wall generally were confined to areas where neighboring meiocytes were in contact. The holes varied in size within locations and between taxa. The largest holes, about 2.4ensp;mu;m diameter, were found inLupinus. Fixation in standard acidndash;alcohol fixatives resulted in marked plasmolysis and loss of cytoplasmic detail, but the nucleolus and bivalents were readily apparent. Fixation in buffered glutaraldehyde, with or without postfixation in OSU4, preserved the cytoplasmic organelles and plasmolysis was minimal, but bivalents could not be distinguished. All fixatives preserved the nuclear membrane so that the nuclear region was clearly delimited from the cytoplasm.