A Cytochemical Study of the Hypertrophied Synergid in Allium cepa L

Abstract

The cytochemical composition of the hypertrophied synergid cell in Allium cepa is studied in relation with egg, zygote and the young embryo by using localization methods for insoluble polysaccharides, nucleic acids and proteins.
The two synergids are larger than the egg cell to begin with and their cytochemical composition is similar to that of the egg cell in having low cytoplasmic polysaccharides, RNA and proteins; their large nuclei show less stainability for DNA. With the organization of the egg apparatus completed, one of the synergids becomes more hypertrophied than the other and both of them possess PAS positive cytoplasm which is rich in RNA and proteins. The nuclei in the synergids are proportionately large and stain with azur A as densely as the nuclei of the somatic cells. The smaller synergid degenerates after fertilization. The hypertrophied synergid, by the side of the zygote, has an immensely large nucleus with chromatin reticulum made of giant chromatin threads-perhaps polytenic in nature. The hypertrophied synergid remains active until the embryo reaches 3-celled stage and degenerates later. The enlarged synergid cell of A. cepa does the functions of absorption, storage and subsequent secretion of nutritional substances required by the egg, zygote and the young embryo.