Summary
Embryogenic pollen ofNicotiana tabacum cv. Badischer Burley is smaller than gamete-forming pollen, and is characterised by an attenuated cytoplasm that is poor in ribosomes and with condensed mitochondria. In these respects, an embryogenic pollen grain resembles the angiosperm egg before fertilization. On culture, such pollen readily form embryos. During embryogenesis the first noticeable feature is the formation of a fibrillar wall around the pollen cytoplasm and within the intine. The significance of this wall is at present uncertain. Following wall formation, there is an increase in density of cytoplasm associated with an increase in the ribosome population. Also there is decrease in opacity of the matrix of the mitochondria and a change in the dilation of cristae. These changes are specific features of pollen embryogenesis, and reflect the transformation of pollen from a dormant to an active state. The other non-specific features of embryogenesis, which are similar to changes occurring in other cells undergoing differentiation, are the appearance of starch in amyloplasts and of lipid droplets.
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Rashid, A., Siddiqui, A.W. & Reinert, J. Subcellular aspects of origin and structure of pollen embryos ofNicotiana . Protoplasma 113, 202–208 (1982). https://doi.org/10.1007/BF01280908
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DOI: https://doi.org/10.1007/BF01280908