Chromosome constitution and nucleolar behaviour in the endosperm of Cucurbita pepo L

At early stages of development the endosperm of Cucurbita pepo L. was found to be triploid with 3n=60. Higher levels of ploidy (6n, 12n, 24n, 48n) were encountered at later stages. The euploid increase in chromosome number is the result of endopolyploidy. The volume of the nucleolus increased with the increase in nuclear volume. Cells with varying numbers of nucleoli of different sizes and shapes were observed in the endosperm at all stages. Fragmentation of the nucleolus is believed to be responsible for the increase in nucleolar number. Signs of nuclear disorganisation in the endosperm were visible from the 17th day onwards. As the endosperm tissue gets absorbed by the developing embryo, the mature seed is non-endospermous.