The present study investigates the effect of long and short term Cd stress in chickpea plants and evaluates the protective effect of exogenous nitric oxide (NO) supplementation using sodium nitroprusside (SNP). Cadmium treatments were given before sowing (long term stress) and thirty days after germination (short term stress). Sodium nitroprusside was given as foliar spray 30 days after germination to both long and short term Cd treated plants. Cadmium adversely affected the membranes as was evident from increased electrolyte leakage and lipid peroxidation levels. Sodium nitroprusside treatments decreased ion leakage and lipid peroxidation levels significantly. Short term Cd stress resulted in a higher induction of the catalase, peroxidase, ascorbate peroxidase, glutathione reductase and superoxide dismutase as compared to long term Cd stress. Nitric oxide showed its positive effect by further increasing the activities of antioxidant enzymes. Cadmium stress also altered the level of antioxidant metabolites by reducing the ascorbate redox ratio (ASC/DHA) and glutathione redox ratio (GSH/GSSG). Sodium nitroprusside treatments increased the redox ratios. Cadmium also adversely affected the seed yield and a greater decline was observed with long term Cd stress as compared to short term Cd stress. Nitric oxide had a positive effect on seed yield and Cd accumulation. The study concludes that an exogenous supply of NO protects chickpea plants from Cd toxicity.
Experiments were conducted to study the effect of ageing of the host and senescence of the nodules on the content and composition of the proteins of leghemoglobin in nodules of cowpea (Vigna sinensis L.). Total and heme protein contents of leghemoglobin were the highest in the red nodules and dwindled with the onset of nodule senescence. In the fully senescent green nodules the total proteins decreased to a very low level, while the heme proteins were almost absent. Disc electrophoretograms of leghemoglobin obtained from red and brown nodules showed nine bands out of which only four gave positive test for heme. Greening of the nodules resulted in a considerable reduction in the intensity of the bands. Senescence of the host plant resulted in a reduction in the number of leghemo‐globin proteins in all types of nodules and brought about a drastic change in their electrophoretic mobility.
Plants of a pure line variety, G 24, of Cicer arietinum L. were grown in sand culture. After an initial dose of a complete nutrient solution, a nitrogen free nutrient solution was supplied to the sand at intervals and a standard rhizobial culture was added twice. The plants were treated with two concentrations of ascorbic acid (20 mg/l and 100 mg/l) through the rooting medium. At suitable intervals two pots from each treatment were sampled. Observations were made regarding the earliest initiation of nodulation, the number, weight and colour of nodules and the nitrogen content of different plant organs under various treatments.
Ascorbic acid (AA) treatments considerably enhanced nodule initiation. AA was found to increase the number and the fresh and dry weights of nodules tremendously and maximally under both concentrations used. The nodules were, on the whole, more pink under AA treatments and their greening was considerably delayed thus increasing their functional span. The nitrogen content of AA‐treated plants was over 2.5 times that in the control. This increase in nitrogen content fully reflected itself in growth by an increase in the weight of all plant organs. Treatment with 20 mg/l AA stands out prominently above all others in this respect. Pod formation started earlier and the pod and seed weights were also much higher in the AA treatments than in the control. Treatment with 20 mg/l AA was on the whole more promotive than that with 100 mg/l.
The enhancement in the nodulation and the functional efficiency of nodules by AA treatments has been attributed to the capacity of AA to increase the loci and rates of cell division by promoting nucleic acid and protein synthesis and its action as a powerful electron donor. The results show that nodulation is yet another phenomenon wherein AA plays the role of an important hormone.
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