## 4 Discussion  
In the present study, the impact of Cd-tolerant, IAA and EPS-producing PGPR strains on growth, physiology, and antioxidant enzyme system of _Brassica juncea_ (L.) plants under Cd-stress was investigated. The scarcity of irrigation water compels farmers to use untreated wastewater and industrial effluents for crop production particularly in developing countries [7; 51]. While it is known that wastewater increases crop production due to  
Figure 4: Effects of Cd-tolerant, IAA and EPS-producing rhizobacterial strains on antioxidant enzymes ((**A**) SOD activity; (**B**) POX activity; (**C**) CAT activity) of _Brassica juncea_ (L.) plants under Cd-stress in pot trial; (\(n=3\)); Means with same alphabets do not differ statistically from one another (\(p\leq 0.05\)). dissolved nutrients and beneficial impacts on soil properties, it is also a source of heavy metals in soils and growing crops [9; 52]. Heavy metals are potentially toxic for plants, animals, and human beings due to their non-biodegradable nature [53; 54; 55]. In response to metal stress, plants produce antioxidants and free radicals in addition to activation stress responsive genes [56]. They produce reactive oxygen species (ROS) in plants that are regulated by production of enzymatic and non-enzymatic antioxidants [55; 57]. These antioxidative enzymes include CAT, peroxidase, SOD, polyphenol oxidase (PPO) and gua-iacol peroxidase (GPOX), etc. [58] while proline is the major non-enzymatic osmoprotectant produced in plants. In our study, Cd-stress decreased plant growth that might be due to reduction of water and nutrient uptake by _Brassica juncea_ (L.) plants exposed to Cd-stress as a result of decreased root growth [18]. Results of our studies are supported with the work of [PERSON] et al. [59] who reported that Cd-stress negatively affected the growth of _B. juncea_. Cadmium stress also decreases the root volume thus changes the size of the root system [60] that affects the exposure of roots to soil, water and nutrients that decrease in crop performance. Plants produce osmolytes as a defensive strategy to cope with stress conditions. Stress tolerance in plants can be induced exogenously by application of osmoprotectants, amendments or inoculation with PGPR having the ability to produce different plant growth regulators or exopolysaccharideadides [61; 62; 63]. These microbes use different mechanisms such as production of exopolysaccharides, ACC-deaminase activity, catalase activity, phyto-hormone production and chitinase activity to induce stress tolerance in crop plants [26; 64]. _Bacillus_ strains are reported to be involved in inducing physiological alterations in plants as an adaptive strategy under stress [65]. The use of Cd immobilizing bacterial strains in combination with different immobilizing amendments have also shown their worth under stress [32]. In the current study, rhizobacteria having the potential to produce EPS and IAA under Cd-stress along with other plant growth promoting (PGP) traits showed their potential to improve growth of _Brassica juncea_ (L.) plants under Cd-stressed conditions. These strains enhanced the root and shoot growth thus improving the total dry matter of _Brassica juncea_ (L.) plants. This increase in plant biomass might be attributed to improvement in root growth due to production of IAA by these strains that led to enhanced shoot growth. It has been well documented in literature that auxins, especially IAA, are involved in root tissue differentiation, cell division and elongation, and root initiation [66; 62]. The potential of _Bacillus araybhattai_ SRB02 to induce oxidative stress tolerance in soybean has been reported by [PERSON] et al. [67] which they attributed to a change in phytohormones level of plants by the inoculated strains. This increase in plant growth might also be due to the production of exopolysaccharidesrides by inoculated strains.