http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/729 2013-05-18T12:09:34Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/748 Lasers as Mutagens Padma Nambisan The use of laser excitations at two wavelengths, 488 rim and 514 nm, produced by Argon ion laser in two plants species, Vicia faba (faba bean) and Allium cepa L., is described to compare the mutagenicity and the spectrum of chromosomal aberrations induced by laser at mitosis. The laser irradiation has been done at two power levels 200 and 400 mW with power densities 2.25 mW cm 2 and 4.49 mW cm 2 and different exposure times (10, 20, 30 and 40 min). The effect produced by laser is compared to those of UV rays and y- radiations. Laser as in the case of other physical and chenucal mutagens causes a dose-dependent decrease in mitotic chromosomal aberrations at these wavelengths. It is postulated that laser could be used as a new radiation system for the induction of mutations. 1998-05-01T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/747 Induction of mitotic aberrations by Argon ion lasers in Vicia faba L. and Allium cepa L. Padma Nambisan A comparative study of the effect of laser in inducing chromosomal aberrations at 488 nm was done in Vicia faba L. (faba bean) and Allium cepa L. (onion) with Argon ion laser (Spectra Physics Model 171). Seeds and bulbs of V. faba and A. cepa were subjected to laser irradiation by 488 nm excitations from Argon ion laser source at power levels 200 and 400 mW with power densities 2.25 mW cm-2 and 4.49 mW cm-2 and different exposure times ( 10, 20, 30 & 40 ..... tc) similar to the effect of other physical and chemical mutagens, laser caused a dose dependent decrease in mitotic index and a rise in mitotic aberrations when compared to the control . In both plant species, mutations were observed in all stages of mitotic cell cycle . The total percentage of aberrations was two fold higher at 400 mW than at 200 mW exposure. 1997-01-01T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/746 Induction of Mitotic Chromosomal Aberrations by Lasers Padma Nambisan Laser irradiation at wavelength 514 nm was used to study the effect, of lasers in inducing chromosomal aberrations at mitosis. This study offers a new radiation system which could be used for the induction of mutations. Results are compared with those obtained from studies using y-rays as irradiation source. 1997-01-01T00:00:00Z http://dyuthi.cusat.ac.in:80/xmlui/handle/purl/745 Comparison of proline accumulation in callus and seedlings of two cultivars of Oryza sativa L. differing in salt tolerance Padma Nambisan Response of callus culture and seedlings of a salt tolerant rice variety, pokkali, was compared to that of a salt sensitive variety, hrswa, under conditions of salinity stress induced by incorporating different quantities of sea water in the culture media. Seedlings of pokkali showed minimal symptoms of salt stress under conditions of low salinity and more severe symptoms including dry of older leaves under high salinity Conditions. However, seedlings of hrswa showed severe stress symptoms even under low salinity and plant death under high salinity conditions. This superior character of salt tolerance of pokkali over hrswa was, however, not observed in callus cultures. In both the cultivars, the severity of symptoms depended on the intensity of stress. Accumulation of free proline in callus cultures and seedlings under stress conditions was monitored. Both pokkali and hrswa accumulated proline in response to stress to the same level. The response was same in callus cultures and in seedlings of both cultivars and the rate of proline accumulation was dependent on the intensity of stress. This, study, thus, indicates that accumulation of proline is not indicative of salt tolerance character in rice. 1994-10-10T00:00:00Z