Comparison of the developmental responses of diploid and tetraploid Phalaris following irradiation of the dry seed-i : Determination of mitotic cycle time, mitotic time and phase time

Abstract

The duration of G 1 S, G 2 and mitotic cycle (i.e. interphase + mitosis) times and phase times (i.e. duration of prophase, metaphase, anaphase, etc.) were compared in the diploid Phalaris canariensis and the tetraploid P. minor. Using the technique of autoradiography with tritiated-thymidine as a DNA precursor, the mitotic labelling index method was employed to estimate G 1, S und G 2 . This, together with a method of cell counting and growth measurement, was also used for determining the mitotic cycle time and phase times. The only observable difference between the two species was the length of S, which was twice as long (6·4 hr) in the tetraploid as in the diploid (3·4 hr).