| Popis: |
Irradiation effects from 60Co at 3.0 kR and 15.0 kR on Sirogonium melanosporum (Randhawa) Transeau and Sirogonium sticticum (J.E. Smith) Kutzing were compared. Sirogonium melanosporum cells exposed to 3.0 kR showed a reduction of cell division from 13.0% to 5.0% with chromosomal fragments occurring in 23.0% of the cells. Chromosomal fragments were not detected in S. sticticum cells exposed to 3.0 kR. In S. melanosporum with 15.0 kR, no cell division was visible on the first day after treatment, but by the third day 1.0% of the cells were undergoing mitosis and chromosomal fragments were present in 52.0% of the dividing nuclei. In S. sticticum exposed to 15.0 kR, cytokinesis but no mitosis was observed on the first day after treatment. However, filaments contained giant cells (;500 μm long) and micro-cells ( 3 0 μ m long ). By days 4 and 13 there were 2.0% and 26.0% giant cells, respectively, when 15.0 kR was applied to actively dividing cells. When cell division was minimal during irradiation treatment, only 5.0% giant cells were produced by day 13. Giant cells contained nuclei over double the length and almost double the width of untreated cells, and observation of 3500 of these cells showed no nuclear division. By contrast, micro-cells lacked nuclei and did not survive. Cells other than giant cells or micro-cells divided actively to produce vigorous cultures of S. sticticum during a 6-month observational period. Filaments of S. melanosporum receiving 15.0 kR survived for only 3 months. |
