HIGH-PRESSURE FREEZE FIXATION REVEALS NOVEL FEATURES DURING ONTOGENY OF THE VEGETATIVE CELL IN LEDEBOURIA POLLEN - AN ULTRASTRUCTURAL AND CYTOCHEMICAL STUDY

The ultrastructure of the vegetative cell in the pollen of Ledebouria socialis Roth (Hyacinthaceae) was investigated from microspore mitosis to anthesis. As a result of the good preservation quality achieved wi th high-pressure freeze fixation and freeze substitution, novel struct ural features were observed. Extensive endomembrane compartments emerg ing at the onset of lipid and starch mobilization, were identified as protein bodies by using video-enhanced contrast light microscopy. Thus , proteins, apart from starch and lipids, represent a third class of i mportant intermediary storage substances in developing pollen. The clo se spatial relationship between protein bodies, endoplasmic reticulum (ER), and storage lipids suggest that protein bodies and ER contribute to lipid digestion. Immediately prior to anthesis the protein bodies become transformed into unspecialized vacuoles as a result of the grad ual dissolution of their contents; the formation of the protein bodies remains still to be elucidated The ER proliferates extensively during pollen ontogenesis, thereby changing its ultrastructure and spatial o rganization. Microfilaments were detected during all developmental sta ges, in particular microtubule-associated single microfilaments. The m icrofilaments are likely to be composed of actin as shown by immunogol d labeling.