Phosphate supply as a promoter of tolerance to arsenic in pearl millet

Many soils are contaminated by heavy metals, with arsenic posing serious environmental threat. Enrichment of soil with phosphate is believed to reduce the arsenic toxicity. However, only a few attempts have already been conducted towards understanding the precise role of phosphate in controlling As toxicity. Moreover, there is no adequate information on the effect of phosphate on As-induced oxidative stress, a major contributor of As toxicity in plant system. Τhe present study aims to determine the effect of varying concentrations of phosphate on As-mediated oxidative stress in pearl millet (Pennisetum typhoides). Our study revealed that a concentration of 100 μM of phosphate was able to protect the test plant from As (100μM)-mediated oxidative stress, as evident from the data on growth and lipid peroxidation. This novel finding was further supported by the increased chlorophyll content of the test plant raised in phosphate supplemented media. Phosphatemediated improvement of antioxidant enzymes, such as SOD (superoxide dismutase), CAT (catalase), and APX (peroxidase), could be a crucial factor in regulating As-induced oxidative stress in pearl millet. The results of the present study suggest that availability of phosphate in the surrounding media has a clearly pivotal role in the generation of oxidative stress in P. typhoides exposed to As.