Metal nanoparticles significantly affect the physiological properties of plants, e.g., seed germination, growth and metabolism. In the present study, the toxic effects of silver nanoparticles (AgNPs) and silver ions were studied on callus cells of two varieties of wheat (Triticum aestivum L.): stress tolerant-Parabola; stress sensitiveRaweta. Stress induced by silver particles or ions (0, 20, 40, 60 ppm) was investigated using different parameters such as morphological characteristics, lipid peroxidation and mobilization of defense system which was determined by analyzing the activity of antioxidant enzymes, glutathione (GSH) and proline contents. Microscopic observations revealed deformation of cells after treatment by sol of higher silver concentrations. An increase in malondialdehyde content in both studied varieties was observed. Tested varieties showed an increased proline content in the silver-treated cells. There was no effect of silver on the superoxide dismutases activity, while the activity of catalase was significantly decreased. The changes in the activity of peroxidases in both varieties were opposite. The highest content of intracellular GSH was noticed at a concentration of 20 ppm of both AgNPs and silver ions. The presented results demonstrate a significant similarity of the effects caused by the studied stressors: silver nanoparticles and silver ions. The results characterized the mechanism of action of nanosilver on wheat callus: morphology disorder, damage to cell membranes, severe oxidative stress and in consequence intensification of production of non-enzymatic antioxidants.
Contents of ethylene, osmoprotectants, levels and forms of polyamines (PAs) and activities of antioxidant enzymes in the leaves and roots were investigated for five wheat cultivar seedlings (differing in drought tolerance) exposed to osmotic stress (-1.5 MPa). Stress was induced by 2-day-long treatment of plants with polyethylene glycol 6000 (PEG) or NaCl added to hydroponic cultures. Nawra, Parabola and Manu cv. (drought tolerant) showed a marked increase in osmoprotectors (proline and soluble carbohydrates, mainly glucose, saccharose and maltose), free PAs (putrescine Put, spermidine Spd and spermine Spm) and Spd-conjugated levels, in both leaves and roots, after PEGtreatments. Radunia and Raweta (drought sensitive) exhibited smaller changes in the content of these substances. The analysis of enzymes involved in proline metabolism revealed the glutamate as a precursor of proline synthesis in PEGinduced stress conditions. The increase in the activity of antioxidative enzymes, especially catalase and peroxidases, was characteristic for tolerant wheat plants, but for sensitive ones, a decrease in superoxide dismutase and an increase in mainly glutathione reductase activities were observed. After NaCl-treatment smaller changes of all biochemical parameters were registered in comparison with PEG-induced stress. Exceptions were the higher values of ethylene content and a significant increase in saccharose, raffinose and maltose levels (only in stress sensitive plants). The proline synthesis pathway was stimulated from both glutamate and ornithine precursors. These results suggest that the accumulation of inorganic ions in NaCl-stressed plants may be involved in protective mechanisms as an additional osmoregultor. Thus, a weaker stressogenic effect as determined as water deficit by leaf relative water content and relative dry weight increase rate and differences in metabolite synthesis in comparison with PEG stress was observed. Proline seems to be the most important osmo-protector in osmotic stress initiated by both PEG and NaCl. The synthesis of sugars and PAs may be stimulated in a stronger stress conditions (PEG).
The aim of the study was to delineate the protective effect of ascorbic acid with plausible mechanism after single and repetitive cadmium administration to Swiss mice. The effects of single high dose administration of CdCl(2) (6 mg/kg) or ascorbic acid (AsA) (50 mg/kg) and chronic (three times) administration of Cd at low dose (2 mg/kg) or AsA at same dose (50 mg/kg) were compared in Swiss albino mice. Changes of lipid peroxidation [determined by the malonyldialdehyde (MDA) concentration] were taken as a measure of the oxidative stress intensity. Lipid fatty acid's unsaturation related to the permeability of cell membranes was also examined. Mobilization of the immune system was determined by analyzing changes in antioxidant concentrations of AsA and glutathione (GSH), and by measuring the activation of antioxidant enzymes SOD, GPx and CAT. In addition, the level of free polyamines and variation in their proportions were examined. In conclusion, exposure to higher levels of cadmium will have more deleterious effects on the body rather than chronic exposure at lower levels with this toxic metal, while this study clearly demonstrated the protective effects of AsA in a mouse model.
The influence of silver nanoparticles on calli cells of stress tolerant-Parabola and stress sensitive-Raweta wheat genotypes (Triticum aestivum L.) was studied. Three types of silver nanoparticles (AgNPs) were tested: cystamine-stabilized (positively charged), unmodified, synthesized using sodium borohydride and citrate-stabilized AgNPs, both negatively charged. Physicochemical properties of silver nanoparticles were investigated by: UV-Vis spectroscopy, dynamic light scattering used for electrophoretic mobility and hydrodynamic diameter determination and transmission electron microscopy. The evaluation of cytotoxicity was estimated basing on lipid peroxidation, proline content and antioxidant enzymes activity. For sensitive variety every type of nanoparticles induced stress (proline increase) in cells, but positively charged nanoparticles were most cytotoxic. Treatment of stress tolerant Parabola by AgNPs caused the increase in SOD activity, suggesting the occurrence of oxidative stress in cells, confirmed by the increase of membrane lipid peroxidation. Negatively charged AgNPs were significantly more cytotoxic to the calli cells of sensitive variety in comparison to tolerant one.
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