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The effects of different concentrations of Al (10 μM, 50 μM, 100 μM) on nucleoli in root tip cells, root growth, antioxidant enzyme activity and malondialdehyde (MDA) content were investigated in hydroponically grown Vicia faba L. Aluminum significantly inhibited root growth of V. faba treated with 50 μM and 100 μM Al. In the nucleolus in root tip cells, some particulates containing argyrophilic proteins were extruded from the nucleus into the cytoplasm, and some were scattered in the nucleus after Al stress. Superoxide dismutase (SOD) activity in leaves and roots exposed to different concentrations of Al was mostly higher than in the control. Seedlings exposed to 100 μM Al showed significantly higher peroxidase (POD) activity in roots than in the control. POD activity increased much more in roots than in leaves. Catalase (CAT) activity was lower in roots than in leaves. Malondialdehyde (MDA) content in leaves and roots of plants exposed to 50 μM and 100 μM Al was significantly higher than in the other groups and the control at 6 to 9 days of treatment. These results suggest that alterations in nucleoli and altered antioxidant enzyme activity and MDA content in V. faba can serve as useful biomarkers for detection of Al toxicity. The mechanisms of Al toxicity and tolerance in V. faba are briefly discussed
We investigated the antioxidant defense mechanism, metal uptake and lipid peroxidation (LPO) levels at different leaf positions in Mentha piperita L. grown in Mn2+-deficient and control conditions. Under manganese deficiency the activity of superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GuaPOX) and the content of ascorbate, chlorophyll, and carotenoid under Mn2+ deficiency were significantly lower than in the control for all leaf positions. SOD activity correlated positively with Mn2+ uptake. Fe2+ uptake was inhibited by Mn2+ deficiency. During early stages of Mn2+ deficiency, M. piperita leaves showed relatively more antioxidant activity and lower LPO. Towards the final stages of the treatment period, comparatively lower SOD, CAT and GuaPOX activity and higher LPO levels accelerated the senescence process.
Salt stress restricts plant performance by disrupting various physio-biochemical processes like photosynthesis. Plants growing in saline substrates show deficiencies in absorption of some essential elements due to the presence of excessive sodium (Na⁺) in the rhizosphere, which antagonizes beneficial cations and causing toxicity in metabolism. Cyanobacteria (CB; a natural biofertilizer) play a fundamental role in building-up soil fertility, thus increasing plant performance. Glutathione (GSH) is a well-known antioxidant, which contributes to increase salt tolerance in the plant. This work was conducted as a pot experiment (sand culture) in 2017 to study the combined effect of CB, applied as seed inoculation, and GSH, applied as foliar spray, on growth, pods and seed yields, the contents of antioxidants, osmoprotectants, and nutrients, and the antioxidative enzymes activities of soybean (Glycine max L., cv. Giza 111) plants grown under saline conditions. At fourth leaf stage (21 days after sowing; DAS), CB-pretreated seedlings were supplemented with NaCl (150 mM) along with Hoagland′s nutrient solution, and at the same time seedlings were sprayed with 1 mM GSH. Samples were taken at 60 DAS to assess morphological, physio-biochemical and antioxidant defense systems attributes. Results showed that the integrative application of CB and GSH under saline conditions was effective in improving significantly the growth characteristics, yield components, photosynthetic efficiency (pigments contents and chlorophyll fluorescence), membrane stability index, relative water content, contents of soluble sugars, free proline, ascorbic acid, glutathione, α-tocopherol, and protein, and activities of superoxide dismutase, catalase, and guaiacol peroxidase. The contents of macronutrients (N, P, K⁺, and Ca²⁺) were also increased significantly in Glycine max plants compared to the stressed control. In contrast, Na⁺ content and electrolyte leakage were significantly reduced. Our results recommend using the combined CB (as seed inoculation) and GSH (as foliar spray) application for soybean plants to grow well under saline conditions.
The influence of L-arginine and Nω-nitro-L-arginine (L-NNA) on lead-induced oxidative stress in kidneys of rats with different resistance to hypoxia was studied. The animals were exposed to lead nitrate (3.6 mg/kg, daily) for 30 d and treated with L- arginine (600 mg/kg) or L-NNA (35 mg/kg) 30 min before each injection of lead nitrate. Lead exposure led to a significant increase in the level of thiobarbituric acid reactive substances (TBARS) in rats with high resistance to hypoxia indicating that lead induced renal oxidative stress. Treatment with L-arginine was effective in decreasing TBARS level for this group of animals. L-arginine was ineffective against lead-induced oxidative stress when given to rats with low resistance to hypoxia. In contrast, administration of L- NNA provided significant prooxidative effect on renal lead-induced oxidative stress in rats with low and high resistance to hypoxia. Renal antioxidant defence system remained sensitive to lead-induced oxidative stress and any of the treatments bv L-arginine and L- NNA.
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