The Formation of Hypertrophied Nuclei in the Endosperm of Allium Cepa L.

SUMMARY

The development of the endosperm in Allium cepa conforms to the free-nuclear type. The cytoplasm of the endosperm at the caecal region is denser, rich in RNA and proteins but low in diffused polysaccharides. There are more triploid nuclei per unit area in this region than elsewhere. The small cells of the hypostase are rich in RNA and proteins. This may well result from the high rate of perfusion of nutrients through the hypostase at this time.

With the beginning of differentiation in the embryonic regions, the supply of nutriments through the hypostase falls. Meanwhile cell walls are laid down in the endosperm. This is accompanied by the association and union of triploid nuclei leading to the production of giant hypertrophied polyploid nuclei. These become distorted in shape and stain intensely with Azur A. The depression in the physiological activity of the endosperm cytoplasm in this region, subsequent to the reduced inflow of nutriments from the hypostase, may play a causal role in this union of triploid nuclei.