Contributions to the Cytology of Endosperm in some Angiosperms — I.Zephyranthes AjaxSprenger

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Abstract
The results of the cytological studies in the endosperm of Zephyranthes ajax Sprenger have been reported. Alpha bromonaphthalene and 8-hydroxyquinoline were found to be very effective in spreading the endosperm chromosomes. The endosperm was free nuclear upto 4 days after pollination. The 5 to 6 day old endosperm was cellular. The endosperm, especially at the free nuclear stage, showed a striking variation in the size and shape of nuclei. The range in length and breadth of nuclei in the 4 day old endosperm, for example, was 16μ to 280μ and 8μ to 160μ respectively. The variation was equally striking in the central and the peripheral region. Polyploidy, aneuploidy, amitosis and nuclear fusion were found to be the main causes for the variation observed in the size and shape of endosperm nuclei. Split anaphases, tripolar spindles and lagging chromosomes were responsible for the formation of nuclei with aneuploid numbers. The normal cytological constitution of the endosperm was regarded tetraploid (4 n = 84) as 85 per cent of the nuclei showed this condition. Analysis of the nucleolar numbers and chromosome counts of the endosperm and root tip nuclei have shown that the number of nucleoli per nucleus cannot be used as an index of polyploidy in Zephyranthes ajax. A study of the nuclei at 2, 4, 6, 8, 10, 12 and 14 days after pollination did not reveal any definite constant relationship between size of nuclei and age of endosperm. The endosperm failure was possibly caused by the cumulative effect of mitotic abnormalities which were exhibited in the form of bridges, laggards and rings. High degree of polyploidy, aneuploidy and amitosis also characterised the degenerating cells of the endosperm.