Irradiated seeds of Phaseolus vulgaris cv. Rajmah using Synchroton X-Ray Beam (BL-07) at RRCAT, Indore at various doses in the range of 0.5 -10 Gy were used to raise the seedling and the growth status at different stages was evaluated. Prior to germination, in the seeds soaked for 24 hours, the water regain remained unaffected by seed irradiation at 1 -10 Gy doses, while the acid phosphatase activity was significantly reduced. Strong correlation (R 2 = 0.685) between irradiation dose and enzyme activity also resulted. Analysing seed irradiation effect on seed development up to 4 days, % germination, germination index (GI), seedling wt, and seedling vigour were non significantly decreased at 5.0 Gy dose. The overall growth of 10 days old seedlings raised from irradiated seeds was substantially reduced at irradiation doses of 2 and 5 Gy exerting strong −ve correlation. Also % germination and seed vigour index (SVI) were prominently decreased due to seed irradiation. The nitrogen status of the seedlings, reflected by nitrate reductase activity (NRA) was significantly reduced in response to irradiation exerting strong correlation. The results demonstrate decreased phosphate mobilization in soaked seeds, time dependent decreased growth being more substantial with longer duration and reduced nitrate assimilation due to seed irradiation with Synchroton X-Ray Beam.
Aluminium is a potent toxicant in acidic soils. The present study was taken up to analyze the effects of Al on enzymes of nitrogen assimilation in excised bean (Phaseolus vulgaris) leaf segments so as to gain an insight of the mechanism involved. Supply of 0.001 to 0.1 mM AlCl 3 to excised bean leaf segments affected the in vivo nitrate reductase activity differently in the presence of various inorganic nitrogenous compounds, being inhibited with 5 mM ammonium nitrate and 10 mM ammonium chloride but enhanced with 10 mM potassium nitrate. Al effect with 50 mM KNO 3 varied with time, showing an increased activity at shorter duration, but decreased at longer duration. Al effect on in vivo NRA was dependent upon the nitrate concentration, thus, inhibiting it at 0, 1 and 50 mM KNO 3 , while increasing at 2 and 10 mM. Further, saturating and non-saturating effects were observed in the absence and presence of Al. Al supply influenced the in vitro NRA also, being increased at 10 mM, but decreased at 50 mM KNO 3. Supply of Al to excised leaf segments substantially inhibited the glutamate dehydrogenase activity in the absence as well as presence of 5 mM NH 4 NO 3 but increased the glutamate synthase activity. Inhibition of specific glutamate dehydrogenase activity by Al supply was also observed. However, specific glutamate synthase activity was increased in the presence of NH 4 NO 3 only. The experiments demonstrated that effect of supply of aluminium on in vivo nitrate reductase activity depended upon nitrogenous source as well as nitrate concentration and it exerted reciprocal regulation of glutamate dehydrogenase and glutamate synthase activities, which depended upon N supply too.
Irradiated seeds of Phaseolus vulgaris cv. Rajmah using Synchrotron X Ray Beam (BL-07) in RRCAT, Indore at doses of 1, 10 and 20 Gy were used to raise the seedling and the effects on growth and biochemical constituents in 4-8 days, old seedlings were analyzed. The seed irradiation effect on seedling development up to about 4-5 days, % germination, seedling length and seedling vigor are significantly decreased at 10 and 20 Gy doses with strong −ve correlation. Other parameters, like relative water content, electrical conductivity and acid phosphatase activity are also decreased. Decrease in various biochemical constituents, like, protein and proline has shown significant reduction at 10 and 20 Gy and phenol at 1-20 Gy. However, peroxidase activity is increased at 1 and 10 Gy. Amongst the antioxidant enzymes, only superoxide dismutase activity has shown significant increase at 10 and 20 Gy. For seed irradiation (1 and 10 Gy) effect on seedling development up to 8 days involving transfer to hydroponic culture after 4 days, in shoot tissue, decrease in nitrate reductase activity and pigment content is observed, while nitrate reductase activity in root tissue is increased. The results demonstrate adverse effects on growth as well as biochemical constituents along with increased antioxidant effect in bean seedlings with irradiation of seeds at high dose of synchrotron X radiations. Also the nitrate assimilation and photosynthetic activity are reduced in shoot tissue with seed irradiation, however, increased nitrate reductase activity in roots suggests the involvement of NO signaling.
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