Salinity stress (NaCl) and heavy metals contamination (CdCl2) are the serious environmental constraints for decreased crop production worldwide. However, the interaction between NaCl and CdCl2 regarding sodium (Na), cadmium (Cd), and chloride (Cl) accumulation in plants has not been completely established. Therefore, the interactive effects of NaCl andCdCl2 on plant growth, Na, Cd, and Cl accumulation in plants, and wheat yield were evaluated. Wheat seeds were cultivated in clay loam soil under greenhouse conditions. After two weeks of sowing, plants were subjected to NaCl at the rate of 0, 50, and 100 mM either alone or in combination with CdCl2: 0, 1, and 2 mM, respectively. The results revealed that increasing NaCl and CdCl2 levels reduced Na and Cd concentrations, whereas enhanced Cl concentrations. Furthermore, moderate levels of CdCl2 and NaCl stresses enhanced the antioxidative enzymatic activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in addition to proline accumulation in wheat leaves. By contrast, 100 mM NaCl in combination with 2 mM CdCl2 enhanced H2O2 accumulation by 105%, which thus decreased the membrane stability index (MSI) by 49% and wheat yield by 27% as compared to 2 mM CdCl2. The reduced Cd toxicity by NaCl or Na accumulation in plant tissues by CdCl2 involved competition between Na and Cd at binding sites, however, enhanced Cl phytotoxicity in plants resulted in the overproduction of H2O2 that was not quenched by antioxidative enzymes, thereby decreased MSI and wheat yield.

Background Oxidative stress mediated by reactive oxygen species (ROS) is a common denominator in arsenic toxicity. Arsenic stress in soil affects the water absorption, decrease stomatal conductance, reduction in osmotic, and leaf water potential, which restrict water uptake and osmotic stress in plants. Arsenic-induced osmotic stress triggers the overproduction of ROS, which causes a number of germination, physiological, biochemical, and antioxidant alterations. Antioxidants with potential to reduce ROS levels ameliorate the arsenic-induced lesions. Plant growth promoting rhizobacteria (PGPR) increase the total soluble sugars and proline, which scavenging OH radicals thereby prevent the oxidative damages cause by ROS. The main objective of this study was to evaluate the potential role of Arsenic resistant PGPR in growth of maize by mitigating arsenic stress. Methodology Arsenic tolerant PGPR strain MD3 (Pseudochrobactrum asaccharolyticum) was used to dismiss the 'As' induced oxidative stress in maize grown at concentrations of 50 and 100 mg/kg. Previously isolated arsenic tolerant bacterial strain MD3 Pseudochrobactrum asaccharolyticum was used for this experiment. Further, growth promoting potential of MD3 was done by germination and physio-biochemical analysis of maize seeds. Experimental units were arranged in Completely Randomized Design (CRD). A total of 6 sets of treatments viz., control, arsenic treated (50 & 100 mg/kg), bacterial inoculated (MD3), and arsenic stress plus bacterial inoculated with three replicates were used for Petri plates and pot experiments. After treating with this MD3 strain, seeds of corn were grown in pots filled with or without 50 mg/kg and 100 mg/kg sodium arsenate. Results The plants under arsenic stress (100 mg/kg) decreased the osmotic potential (0.8 MPa) as compared to control indicated the osmotic stress, which caused the reduction in growth, physiological parameters, proline accumulation, alteration in antioxidant enzymes (Superoxide dismutase-SOD, catalase-CAT, peroxidase-POD), increased MDA content, and H2O2 in maize plants. As-tolerant Pseudochrobactrum asaccharolyticum improved the plant growth by reducing the oxidation stress and antioxidant enzymes by proline accumulation. PCA analysis revealed that all six treatments scattered differently across the PC1 and PC2, having 85.51% and 9.72% data variance, respectively. This indicating the efficiency of As-tolerant strains. The heatmap supported the As-tolerant strains were positively correlated with growth parameters and physiological activities of the maize plants. Conclusion This study concluded that Pseudochrobactrum asaccharolyticum reduced the 'As' toxicity in maize plant through the augmentation of the antioxidant defense system. Thus, MD3 (Pseudochrobactrum asaccharolyticum) strain can be considered as bio-fertilizer.