Short duration of the mitotic and endomitotic cell cycle in the heterochromatin-rich monocot

Fraction labeled mitoses curves and caffeine-induced binucleate cell populations, respectively, were used to determine the duration of the mitotic and endomitotic cycle in roots of Allium carinatum, a leak with a 2C DNA content of 22.4 pg and a high proportion of heterochromatin. The mitotic cycle lasts, on an average, 8.1 h, the endomitotic one 7.5 h. These relatively short times (with respect to the nuclear DNA content) are discussed in the view of a possible role of heterochromatin in shortening cell cycle duration and possible advantage of the endomitotic cycle for rapid cell and tissue growth.