ISSN:
1615-6102
Keywords:
Attenuated cytoplasm
;
Embryogenic pollen
;
Exine
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Pollen grains capable of embryogenesis were selectively isolated from (a) near-mature buds from plants induced to flower in short days and low temperature (8 hours light and 18 °C) and (b) young buds from these plants with an additional low temperature treatment (10 °C for 10 days) and fixed for electron microscopy. The pollen from the former formed embryos at a very low frequency in culture, and at the subcellular level showed different degrees of regression of cytoplasm and mitochondria. On the contrary, cold-treated pollen were characterized by a high frequency of embryogenesis, up to 25% of the cultured pollen. They did not show regression of cytoplasm or organelles but had an attenuated cytoplasm which was not rich in ribosomes. Another noteworthy feature of embryogenic grains was the condensed nature of mitochondria. These characteristics of embryogenic grains indicate that they are repressed for gametophytic differentiation. The embryogenic pollen did not differentiate from gametophytic pollen which were very distinctive, having a thick exine, and dense cytoplasm rich in ribosomes. The close similarity of embryogenic grains with young microspores in terms of thin exine and sparse cytoplasm is suggestive of an indeterminate state and that determination into gametophytic or sporophytic (embryogenic) type is probably the function of differential gene activity. Of interest, in this context, is the condensation of mitochondria in embryogenic grains. The relationship, if any, between mitochondrial condensation and embryogenesis remains to be resolved.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01276837
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