Effects of Inoculation with Rhizospheric Pseudomonas on Physiological Responses in the Broad Bean (Vicia Faba) Grown Under Copper Stress

The accumulations of chemical pesticides residues in soils represent one of the greatest risks for the environment and especially for plants. The copper bioviability in rhizosphere is the clearest aspect of this pollution process, causing high levels of metal stress, reducing crops yield by altering physiological and biochemical processes in plants. To face such risks, researchers have frequently studied the effect of plant growth promoting rhizobacteria (PGPR) as enhancer of the plant growth under abiotic stress. The goal of this study was firstly to know the level of broad bean tolerance to metal stress of copper, and its physiological effects in the plant, on the one hand, and the role of plant-Pseudomonas interaction in enhancing the plant tolerance level to metal stress, on the other. In this study, three Pseudomonas strains were isolated and screened by salinity and copper tolerance, then they were individually used as an inoculum in rhizosphere of broad bean Vicia faba (OTONO variety) in the presence of 0; 2.5; 10 and 20 mM.L^-1 of CuSO₄. According to the obtained results, under copper stress conditions with and without bacterial inoculation, the production of biomass and total chlorophyll content were significantly decreased. Copper treatments increased proline content in inoculated plants with P7 and P15 strains and in those which were not inoculated. However, this content was decreased in inoculated plants with P1 strain. The inoculation with P1, P7 and P15 strains motivated the production of fresh biomass and accumulation of proline, and otherwise decreased total chlorophyll content in plants.