Cytoplasmic Structure of Germinated and Ungerminated Pollen Grains ofTradescantia Virginiana

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Abstract
Germinated and hydrated ungerminated pollen grains of Tradescantia virginiana were examined by light and electron microscopy. Contrary to previous generalisations these binucleate grains were found to possess highly organised cytoplasmic structures. They were able to germinate within a few minutes and achieve maximum rates of tube extension immediately. Quantitative studies showed that the secretory vesicle population in the grain cytoplasm was substantial (5.3 × 105 vesicles per grain), though not as large as reported for trinucleate grains. It is concluded that these binucleate grains are intermediate in their characteristics between slow germinating binucleate pollen grains and rapidly germinating trinucleate grains.