Cytology of coconut endosperm

Abstract

The cytology of coconut endosperm was studied from tender nuts from an ordinary tall variety of coconut palm. Cellular endosperm development becomes visible in nuts about 6 months old, at which stage a thin coating of jelly-like endosperm tissue is seen around the periphery of the large embryo-sac cavity. The endosperm tissue is thicker at the antipodal end. The nuclei in the young coconut embryos are diploid (2n = 32), and they divide by normal mitosis. Nuclei of varying sizes were observed in the endosperm tissue, and they showed very active mitosis, the frequency of division being higher in regions nearer to the micropyle. Three different chromosome counts were made in the dividing nuclei, 48 (3n), 96 (6n), and 192 (izn). This shows that increase in size of nuclei is due to euploid increase in chromosome number. In addition to normal mitosis, a C-mitotic type of division was also observed in the 3n and 6n nuclei, and it is suggested that this type of aberrant mitosis is responsible for the attainment of higher levels of ploidy in coconut endosperm.