Modified fast rejoining of chromosomes after fractionated X-ray exposures with iron and copper sulfate pretreatments related to uptake detected by PIXE analysis in Nigella damascena seeds

Nigella damascena dry seeds were irradiated with X-rays (250 kV) at fractionated exposures (2 x 40 and 2 x 20 Gy) separated by time intervals ranging from 120 to 240 s. A decrease of chromosome aberrations (threshold) observed with Co-60 gamma-rays between 130 and 140 s was confirmed. Some seeds were supplemented with FeSO4 or CuSO4. In unirradiated seeds, FeSO4 (at doses ranging from 1 x 10(-5) to 1 x 10(-2) M) induced a certain amount of chromosome damage, ostensibly on the basis of free radical production. FeSO4 (1 x 10(-5)M) pretreatment considerably enhanced the frequency of chromosome aberrations induced by X-rays and suppressed the threshold observed in control experiments. CuSO, (1 x 10(-5) and 1 x 10(-3) M) did not modify the initial level of chromosome aberrations (time intervals shorter than 130 s), but enhanced the final level (time intervals longer than 140 s), thus reversing the threshold. In the present experiments, no modifications of the proportions of various kinds of aberrations occurred as compared with the controls. The enrichment of seeds with each of the transition metals was measured with PIXE (particle-induced X-ray emission) in relation to the biological effects at the chromosome level. (C) 1997 Elsevier Science B.V.