ULTRASTRUCTURAL OBSERVATIONS ON ANTHER TAPETUM DEVELOPMENT OF FREEZE-FIXED LEDEBOURIA-SOCIALIS ROTH (HYACINTHACEAE)

The tapetal ultrastructure of high-pressure-frozen, freeze-substituted Ledebouria socialis Roth (Hyacinthaceae) is described from the tetrad stage up to microspore mitosis. Cytoplasmic degeneration of the tapet um occurs after microspore mitosis. During the tetrad stage and the ea rly free-microspore stage the tapetum cells appear to be meristematic; after callose dissolution they show an intense exocytosis of polysacc harides into the anther locule. Later, the tapetum cells are character ized by abundant endoplasmic reticulum (ER). Highly osmiophilic pollen kitt precursor substances accumulate within distinct, partly irregular shaped cytoplasmic domains (''osmiophilic bodies''), which are intima tely associated with the ER. It remains to be verified whether or not these bodies are derived from the ER. Because of their preservation an d staining patterns the contents of these bodies are tentatively inter preted as flavonoids, one of the main pollenkitt pigments in angiosper ms. Apart from these pigment bodies, there exist four other kinds of l ipophilic inclusion within the anther (cells). The general aspects of lipid preservation in freeze-substituted samples are discussed. Staini ng with hot alcoholic phosphotungstic acid yielded good contrast of th e ER and other membranes, which are often difficult to visualize in fr eeze-substituted, resin-embedded samples.