Role of nitric oxide molecule in the tolerance to arsenic in plants: signal or antioxidant?

Effect of nitric oxide (NO) in mitigating stress induced by arsenic (As) was assessed in Pistia stratiotes, with NO supplied in the form of SNP. Plants were exposed to four treatments: control, SNP (0.1 mg L-1), As (1.5 mg L-1) and As + SNP (1.5 and 0.1 mg L-1, respectively), for 24 h. The absorption of As triggered various changes, as the increased production of reactive oxygen intermediates and the damage to cell membranes. These effects were attenuated by SNP, which participated directly as an antioxidant, eliminating the superoxide anion, and as signaling, inducing an increase in the concentration of antioxidant enzymatic.