Abstract
The purpose of the present study was to detect and explain the various types of chromosomal abnormalities resulting from seed irradiation and to evaluate the frequency of abnormal cells in different doses and thereby establish the relative radiosensitivity between the 2x (2n=14) and c-4x (2n=28) (colchicine-induced) Corchorus capsularis. Air-dried seeds of the two ploidy levels were exposed to 60, 70 and 80 KR gamma-rays (60Co) and different stages of the mitotic division of the treated and control root tips were studied. There was no chromosomal abnormality in the untreated root-tip cells of both the types. The aberrations in the irradiated samples included: a) only bridges, b) only laggards and c) both bridges and laggards in the anaphase of root-tip cells of both the ploidy levels, d) much more variation in length of metaphase chromosomes in c-4x capsularis. Plausible causes of the origin and occurrence of the abnormalities have been discussed in the light of the findings of other workers in the field. There was increase in the frequency of abnormal cells with the increase in radiation dose in both the ploidy levels but at a given dose c-4x capsularis produced more aberrations than the 2x diploid. It was concluded that the artificially induced autotetraploid was more radio-sensitive than the 2x type. This perhaps, was due to the artificial nature of origin of the autotetraploid and its lack of sufficient adaptation to protect itself from radiation effect.