Legume–microbial interactions focus mainly on Rhizobium. The present study aimed to evaluate the plant growth-promoting (PGP) potential of bacterial and cyanobacterial formulations and variety-specific differences following their inoculation in two varieties of pea (Pisum sativum L.), namely Arkel and GP-17. Providencia sp. PW5–Anabaena laxa CW1 treatment was the most promising, with an 11%–76% increase in defense enzyme activity in both varieties. Interestingly, Arkel responded better in terms of nitrogenase activity, which was enhanced several-fold in the inoculated treatments, and exhibited a significant correlation (r = 0.787, 0.778, 0.755; p < 0.05) with shoot length, fresh weight and nodule number per plant, respectively. Nodule number was significantly correlated (r = 0.74, 0.81; p < 0.05) with PAL and PPO activity, respectively, and with microbial biomass carbon, alkaline phosphatase and dehydrogenase activity (r = 0.582, 0.538, 0.666; p < 0.05), respectively. Variety GP-17, however, responded better in terms of increasing the polysaccharide and glomalin content of soil. This study reveals the promise of co-inoculation of PGPRs (plant growth-promoting Rhizobacteria) as synergistic partners for improving plant growth mobilization of major nutrients in pea. However, there is a need to study root exudate patterns to identify promising microbe–variety combinations.
An investigation was undertaken to analyze the effect of four different metal nanoparticles (ZnO, SiO2, Fe2O3 and MgO) on the growth of mung bean (Vigna radiata L.) plants. Agar overlay method using seedling nutrient medium containing 50 and 100 mg l−1 of each of the nanoparticles (NPs) was used for the study undertaken for 28 days. A concentration-dependent increase in fresh weight and carotenoid concentration was recorded in MgO NPs. ZnO NPs showed the highest enhancement in leaf peroxidase activity over control. Heavy metal analysis by ICP-MS of seedlings at both concentrations of NPs for 28 days showed a twofold increase at the higher concentrations with ZnO and Fe2O3 NPs. Visual and SEM observations of the MgO NP-treated roots revealed an increase in density and fibrosity, with unique globular structures on the surface of the roots. MgO nanoparticles–mung bean interaction can be a model system for investigating beneficial interactions of nanoparticles with plants.