Histochemical Studies on the Female Gametophyte of Argemone mexicana L

Abstract

A qualitative histochemical analysis of insoluble polysaccharides, starch, RNA and total proteins during the development of female gametophyte of Argemone mexicana L. has been conducted. Ontogenetically, the plant exhibits a monosporic, Polygonum type of embryo sac.
Cytoplasmic polysaccharides and starch grains exhibit considerable changes during megagametogenesis. At the archesporial stage, the nucellus stains uniformly. From the MMC to the tetrad stage, the walls of these cells take a deeper stain than the cytoplasm. The degenerating megaspores stain very intensely. Wall of the egg is weakly PAS positive in the chalazal region, but stains strongly in the micropylar region. Synergids also stain intensely in the micropylar region. Antipodals have a PAS positive wall all around, but the cytoplasm is weakly positive.
Nucellar cells under the MMC start accumulating starch grains and the number increases till the formation of functional megaspore. In the coenocytic stages and the mature embryo sac, larger grains are found in cells closer to the embryo sac and smaller grains in cells away from the embryo sac.
RNA and total proteins parallel each other in their distribution. The archesporial cell stains moderately for them. There is a decline in the staining intensity in MMC. There seems to be no conspicuous difference in the distribution of RNA and total proteins in the four megaspores in a tetrad. Nucellar cells near the MMC and subsequent stages of megasporo and megagametogenesis show lesser staining for these metabolites as compared to the cells away from MMC. This trend continues till the mature embryo sac stage, when the chalazal nucellar cells stain deeply for RNA and total proteins. Among the constituents of the embryo sac, the antipodals appear to be the most metabolically active, as is revealed by the staining intensity.