Nitric oxide donor, sodium nitroprusside, mitigates mercury toxicity in different cultivars of soybean.

The present study reveals the effect of mercury (Hg) and sodium nitroprusside (SNP) on plant growth and metabolism in soybean cultivars (Pusa-24, Pusa-37and Pusa-40). Mercury stress decreased growth and biomass yield, and gas exchange attributes in all soybean cultivars. External supplementation of SNP mitigated Hg toxicity by improving growth and gas exchange parameters. Electrolyte leakage (EL) increased accompanied with elevated levels of malondialdehyde (MDA) and H2O2 under Hg stress, however, they were found to be reduced in all cultivars upon the exogenous application of SNP. The activities of anti-oxidative enzymes, superoxide dismutase and catalase (SOD and CAT) and those enzymes involved in the ascorbate-glutathione pathway were impaired by Hg stress, but they were regulated by the application of SNP. Accumulation of Hg and NO in the shoots and roots were also regulated by the application of NO. Although, all three cultivars were affected by Hg stress, Pusa-37 was relatively less affected. Mercury stress affected the growth and development of different soybean cultivars, but Pusa-37 being tolerant was less affected. Pusa-37 was found to be more responsive to SNP than Pusa-24, Pusa-40 under Hg toxicity. The external supplementation of SNP could be a sustainable approach to economically utilize Hg affected soils.