“Effect of co-applied plant-mediated zinc oxide nanoparticles and nickel-resistant PGPR on morphological, physiological, and biochemical attributes of chickpea ( <i>Cicer arietinum</i> L.) under nickel stress”

Pulses are essential crops but face challenges from abiotic and biotic stress, especially heavy metal stress, which significantly affects chickpea growth. The focus of the current research was to evaluate the effect of co-applied ZnO-NPs and Ni-resistant plant growth-promoting rhizobacteria (PGPR) for growth and development of chickpea while minimizing nickel stress. A pot experiment was conducted to check the phytotoxicity threshold of ZnO-NPs, with foliar application of ZnO-NPs at concentrations of 0, 25, 50, 75, and 100 mgL^-1, along with PGPR strains (<i>Shewanella</i> sp. and <i>Bacillus flexus</i>). The individual and combined effect of ZnO-NPs (100 mgL^-1) and PGPR (<i>Shewanella</i> sp.) was also checked against Ni stress in chickpea and an average reduction in Ni toxicity of up to 48.6% was detected, where antioxidants, photosynthetic, and growth parameters were increased in co-application of both the bio stimulants, while oxidants decreased significantly. The significant improvement was noticed by photosynthetic parameters such as chlorophyll a and b upto 35.8% and 38.09%. Root and shoot length were enhanced by 28.7% and 34.9% in the combined application in comparison to the control, respectively. It is concluded that biosynthesized ZnO-NPs and <i>Shewanella</i> sp. PGPR together could be optimal to treat Ni stress and to improve chickpea yield.