The effects of nucleotype and genotype upon pollen grain development in Hyacinth and Scilla

In pollen grains within anthers of a triploid Hyacinthus orientalis the average duration of the mitotic cycle and the average size of pollen grains are directly proportional to the nuclear DNA amount. The average length of chromosomes at metaphase of the first pollen grain mitosis decreases with increasing nuclear DNA amount. These findings confirm the control imposed by the nucleotype on the cell phenotype.

In pollen grains of a triploid Scilla sibirica, a species less tolerant of aneuploidy than Hyacinthus orientalis, the evidence indicates that nucleotypic effects are, to a large degree, confounded by genic effects. Genic imbalance in aneuploid grains impedes their progress through the mitotic cycle. To generalise, we conclude that the nucleotype imposes constraints upon the mitotic cycle and other aspects of the cell phenotype but that the constraints may be confounded by modifications superimposed by interaction with genic effects.