Role of biochar in mitigating nickel stress in spinach (Spinacea oleracea L.) plants

Abstract

Increasing nickel (Ni) concentration in plant cells causes physiological, metabolic and cellular alterations, which causes severe damage to the plants. Among various strategies to reduce Ni toxicity in plants, the use of biochar (BC) is very feasible method as it has potential to immobilize Ni which ultimately causes soil remediation. The present study was conducted to determine the role of BC in mitigating Ni stress. Two varieties of spinach (Desi and Green Gold), were subjected to BC (16.25 and 32.5 g) and Ni (5 mM) treatment. Results revealed that the length, fresh and dry weight of shoot and root were improved by application of BC at 32.5 g, however, application of Ni reduced all studied growth parameters. Among photosynthetic pigments, chlorophyll (chl) a, chl b, total chl and carotenoids were also improved at 32.5 g BC under Ni stress conditions. Biochar reduced the concentration of malondialdehyde (MDA) and hydrogen peroxide (H2O2) at 32.5 g by increasing enzymatic antioxidant superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) while, Ni stress raised the concentration of MDA and H2O2. Among organic osmolytes, BC at 32.5 g improved the concentration of glycine betain, total soluble proteins and total soluble sugars and lowered the toxic effects of Ni stress. The uptake of mineral ions such as Ca2+ and K+ were improved and Na+ concentration was reduced by applying BC at 32.5 g under Ni stress conditions. In conclusion, the application of BC at 32.5 g/ pot enhanced plant growth, photosynthetic pigments, osmolytes, antioxidants, ionic contents and lowered oxidative stress determinants to ameliorate Ni stress condition.