Eco-friendly role of serratia marcescens and pseudomonas fluorescens in enhancing rice growth and mitigating cadmium toxicity via uptake modulation and antioxidant regulation.

Plant growth-promoting rhizobacteria (PGPR) offer sustainable means to enhance crop resilience under environmental stress, including heavy metal toxicity. Understanding their role in mitigating such stresses is vital for advancing biotechnological strategies aimed at food security and sustainable agriculture. A pot experiment was conducted to determine the effects of single and/or combined application of different levels [10 and 20 ppm] of Serratia marcescens and Pseudomonas fluorescens on Cd accumulation, morpho-physio-biochemical attributes of rice (Oryza sativa L.) exposed to severe Cd stress [0 (without Cd stress), and 100 µM)]. The research outcomes indicated that elevated levels of Cd stress in the soil significantly (p ≤ 0.05) decreased plant growth and biomass, photosynthetic pigments, and gas exchange attributes. However, Cd stress also induced oxidative stress in the plants by increasing malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), which also induced increased compounds of various enzymatic and non-enzymatic antioxidants and also the gene expression and sugar content. Furthermore, a significant (p ≤ 0.05) increase in proline metabolism, the ascorbate-glutathione (AsA-GSH) cycle were observed. Although, the application of S. marcescens and P. fluorescens showed a significant (p ≤ 0.05) increase in plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds, and their gene expression and also decreased oxidative stress. In addition, the application of S. marcescens and P. fluorescens enhanced cellular fractionation and decreased the proline metabolism and AsA-GSH cycle in O. sativa plants. Research findings, therefore, suggest that the application of S. marcescens and P. fluorescens can ameliorate Cd toxicity in O. sativa, resulting in improved plant growth and composition under metal stress, as depicted by balanced antioxidant defense mechanism.