A sequence of changes in the nucleus resulting in division of the chromosomes, as in * mitosis , but no separation of the chromatids into daughter nuclei. The resulting nucleus is therefore * polyploid. The process can be induced in isolated tissues by treatment with colchicine, which prevents spindle formation so the * centromeres of the daughter chromosomes are unable to move apart into separate nuclei. It may occur as an error in part of a plant, producing, for example, a tetraploid branch on a diploid plant. It occurs as a normal feature in some tissues of higher plants, e.g. the phloem cells of some leguminous plants are polyploid. This type of polyploidy, where some of the cells of a plant have more than the normal complement of chromosomes for the species, is known as endopolyploidy. If endomitosis occurs in cells in the germ line or during the second division of meiosis then unreduced gametes may result. |
