Plant growth hormones have been known to influence mitotic index value (Kato 1955, McManus 1960, Humphries and Wheeler 1960, Davidson and MacLeod 1966, Prasad and Das 1977 and to modify radiation-induced chromosomal damage (Guttman and Brown 1959, Magdon 1964, Araratyan and Azatyan 1974, Araratyan and Vardanyan 1976.The effects of x-rays singly and in combination with IAA and GA3 on mitotic index and modification of chromosomal damage in root meristem of Allium cepa by pre and post-irradiation treatments with these growth hormones have been reported. Material and methodsRoot meristem of Allium cepa, grown from bulbs, formed the material of the present investigation.D etermination of mitotic index Mitotic index (MI) was determined in control and treatments with 84 and 126 R x-rays, 25ppm of indole acetic acid (IAA), 50ppm of gibberellic acid (GA3) singly and in combination of x-rays and growth hormones.Root tips from roots of suitable length of control and treated materials were fixed in a mixture of propionic acid and ethyl alcohol (1:3v/v) 1, 3, 6, 9, 12 and 24hr after treatment.Temporary squash preparations were made using propionic orcein as the stain. Cells with mitotic stages from prophase to telophase were scored against total number of cells observed in microscopic fields from coded slides ar ranged randomly.Modification of x-ray-induced chromosomal damage Root meristems were treated with different concentrations of IAA and GA3 before and after treatments with 84 and 126 R x-rays. The materials kept in dis tilled water served as control.Pre-irradiation treatment: Growing roots were placed in aqueous solutions of 25, 50 and 100ppm IAAA and 50, 100 and 200ppm GA3, and distilled water (con trol) in such a way that only the root tips were immersed in them for 24hr. After the treatments the roots were thoroughly washed in water. The superficial water was wiped off and the roots were irradiated with 84 and 126 R x-rays. The roots were again kept immersed in water for 24hr before fixation.
It has been reported that protection can be provided against radiation damage on plant cells after treatment with kinetin (Mandal Basu 1979), and IAA and GA, (Mandal and Basu 1981). In continuation of our study on radiation protection, the yield of X-ray-induced chromosomal aberrations in the root meristems of Allium cepa, Crotalaria juncea and Lens esculenta after pre-and post-treatment with colchicine was investigated. Materials and methodsIntact roots of Allium cepa, growing from bulbs, and of Crotalaria juncea and Lens esculenta, growing from seeds, were treated with colchicine prior to and after exposure to X-rays. Treatment with X-raysRoots of A. cepa were treated with 84 and 126R and those of C. juncea and L. esculenta with 880R and 336R X-rays respectively, using a Philips Contact and Cavity therapy tube, which was run at 50kV, 2mA current, 0.5mm Al filter and 12cm target distance, giving a dose rate of 3.5R/sec as measured by a Victoreen dosimeter. Treatment with colchicineFor pre-irradiation treatment, the root meristems of A. cepa and C. juncea were kept immersed in 0.02 and 0.05per cent and of L. esculenta in 0.01 and 0.02 per cent aqueous solution of colchicine (manufacturer:Russel-Uclaf, France) for one hour. Similarly, roots of all the plants were also kept immersed in distilled water for the same period, which served as control. The materials were then washed in water and the superficial water was removed before irradiation.After irradia tion the roots were allowed to revive in water for 24hours.In case of post-irradiation treatment, the roots were first irradiated and then treated with colchicine. The X-ray doses, colchicine concentrations, duration of treatment and revival remained the same as in pre-irradiation treatment.For cytological study, root tip squash preparations were made after fixation in a mixture of propionic acid and ethyl alcohol (1:3v/v) and staining in propionic orecin.Scoring of X-ray induced chromosomal aberrations at anaphase and telophase stages was made from coded slides arranged randomly and by one person.
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