Mitotic cycle kinetics of root meristems of isolated barley embryos and intact seedlings. Labelling of nuclei by3H- thymidine and its cytogenetic consequences

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Abstract
The duration of the mitotic cycle and its individual phases was estimated in root meristems of isolated barley embryos and intact barley seedlings by means of pulse labelling with3H-thymidine and construction of labelled mitoses curve. The duration of the whole mitotic cycle in the cell population of root meristems of isolated barley embryos cultivated in the aerated liquid complete medium is 12.2 h. The mitotic cycle time of root meristems of intact barley seedlings, oultived in Petri dishes on wet blotting paper is 9.2 h. Most of root meristem cells belong to the fraction of rapidly proliferating cells, but this fraction exerts a high degree of variability by itself. Pulse treatment by3H-thymidine in our experimental conditions (74 kBq ml-1 - or 2 μCi ml-1, exposure 0.5 h) did not induoe any chromosomal aberrations in unlabelled cells and only a very low frequency of chromosomal aberrations in labelled cells. Measuring the cell population kinetics by pulse labelling with3H-thymidine can be used simultaneously with the study of induction of ohromosomal aberrations by mutagens.