Mitotic Cycles and Mitogenesis in Micrasterias

抄録

The variation of the length of the mitotic cycle had been studied in normal haploids, in different types of diploids, and in artificially produced binucleate and other cell types of diverse Micrasterias species. The cycle is shortest in some double cells with a relative large number of plasmastructural units. In some cases also the diploid may divide at the highest rate. In double cells a short interval occurs when only one end of the cell has divided in the preceding division and the other end has hence had time to reach maturity earlier than the former.
The mitotic cycle is shorter in haploid than in diploid cells. The uniradiate haploid cells divide at a lower rate than normal biradiate haploid cells and, at least in some species, biradiate diploid cells at a lower rate than triradiate diploid cells.
In the binucleate cells, including the heterocaryotic types, i.e. cells with one haploid and one diploid nucleus, the mitosis takes place simultaneously at both isthmuses.
The dependence of the mitotic cycle on the nucleocytoplasmic ratio and the mitogenesis problem are discussed.