Abstract
The stages of tapetum development are characterized by the accumulation of substantial intracellular lipid deposits. Much of the pollen coat material, which is essential to pollen-stigma recognition and pollen germination, derives from tapetal lipid bodies found in two types of organelles: tapetosomes and elaioplasts. Tapetosomes are single-membrane-enclosed organelles containing relatively large lipid-rich structures; elaioplasts originate from plastids by the gradual accumulation of osmiophilic droplets. We examined the ultrastructures of anthers by cryo-fixation using a high pressure freezing method. In wild-type tapetal cells, the elaioplasts showed poor electron density on cryo-fixation, while they contained osmiophilic materials on chemical-fixation. In contrast, the tapetosomes showed high electron density on both of cryo- and chemical-fixation. We found the exocytosis of large osmiophilic particles and small particles containing few contents. It is possible that the large particles derived from tapetosomes and the small particles derived from elaioplasts.
