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Plant growth-promoting endophytic bacteria can stimulate the growth, nutrient acquisition, symbiotic performance and stress tolerance of chickpea plants under saline soil conditions. The aim of this study was to investigate the stress-adaptive mechanisms of chickpea plants mediated by Bacillus subtilis (BERA 71) under saline conditions. Inoculation with BERA 71 enhanced plant biomass and the synthesis of photosynthetic pigments and reduced the levels of reactive oxygen species (ROS) and lipid peroxidation in plants under conditions of stress. Furthermore, the activities of ROS-scavenging antioxidant enzymes (superoxide dismutase, peroxidase, catalase and glutathione reductase), the levels of non-enzymatic antioxidants (ascorbic acid and glutathione) and the total phenol content were increased in stressed plants during bacterial association. The bacteria decreased sodium accumulation and enhanced the nitrogen, potassium, calcium and magnesium content in the plants. The suppression of ROS generation and of lipid peroxidation and the accumulation of proline in BERA-71-inoculated plants enhanced the membrane stability under salinity stress and non-stress conditions.

Experiments were conducted to investigate the role of silicon (Si, 2 mM potassium silicate - K2SiO3) in ameliorating the salinity (200 mM NaCl) triggered growth retardation, photosynthetic inhibition and the oxidative damage in Talh trees (Acacia gerrardii Benth). Salinity stress reduced length and dry biomass accumulation of root and shoot which were significantly improved by Si supplementation. Application of Si enhanced the synthesis of photosynthetic pigments including chlorophyll a, chlorophyll b, total chlorophylls and carotenoids resulting in greater photosynthetic activity measured in terms of net CO2 assimilation. Stomatal conductance and transpiration rate were declined due to NaCl treatment and supplementation of Si ameliorated the negative impact of NaCl on these attributes and was significantly improved when applied to normal grown plants. Further, lipid peroxidation was more in NaCl stressed plants without Si as compared to those supplemented with Si. Si protected Talh trees from NaCl induced oxidative damage by improving the activity of antioxidant enzymes (SOD, POD, CAT, APX and GR) and the content of ascorbic acid. Accumulation of compatible osmolytes including proline and glycine betaine was increased due to Si supplementation leading to improved growth under saline conditions in addition Si supplementation mitigated the deleterious effects of NaCl on flavonoid content. More importantly Si supplementation prevented excess uptake of Na and also protected the ill effects of excess Na on the uptake and accumulation of K and Ca resulting in significant decline in Na/K ratio. In conclusion, Si mitigates the negative effects of NaCl in A. gerrardii by modifying nutrient uptake, osmolytes accumulation and up-regulating antioxidant system. Keywords: Acacia gerrardii Benth, Osmolytes, Photosynthesis, Antioxidants, NaCl stress, Nutrient uptake, Silicon

The aim of this study was to evaluate cadmium stress induced changes in the growth, lipid peroxidation and antioxidant activity of Bassia indica associated with arbuscular mycorrhizal fungi (AMF) and their amelioration by calcium application. Cadmium stress can cause alterations in the physiological and biochemical processes in plants. A calcium application combined with an AMF treatment resulted in the reduction of lipid peroxidation and the production of hydrogen peroxide, thereby mediating the mitigation of cadmium induced oxidative stress. The activity of antioxidant enzymes increased with cadmium application, whereas AMF inoculation combined with a calcium application further enhanced their activity. An increase in the content of non-enzymatic antioxidants such as ascorbate, reduced glutathione (GSH), oxidized glutathione (GSSG) and S-nitrosoglutathione (GSNO) in AMF-inoculated and calcium-treated plants further suggests their role in strengthening the antioxidant defense system that results in maintained growth. The application of calcium combined with the AMF treatment caused a significant reduction in lipid peroxidation and in the production of hydrogen peroxide, thereby mediating the mitigation of the cadmium induced oxidative stress. Increased proline accumulation was clearly evident in stressed plants, and the calcium application as well as the AMF inoculation further induced proline synthesis, thereby providing efficient protection against cadmium stress by increasing the maintenance of the systemic resistance criteria. Keywords: Bassia indica, Cadmium, Calcium, AMF, Acquired systemic resistance