The role of sodium nitroprusside (SNP) in alleviating cadmium stress in maize plants

Cadmium (Cd) is a heavy metal that is highly toxic to plants and animals and can accumulate in the environment as a result of industrial activities and agricultural application of some types of phosphate fertilizer. This study aimed to assess the role of sodium nitroprusside (SNP), as a source of nitric oxide (NO) in alleviating Cd stress in maize plants. Maize plants were kept in soil saturated with 40%-strength nutrient solution in a greenhouse, and cadmium nitrate, Cd(NO₃)₂, was applied at different concentrations, (0, 10, and 50 µM). Sodium nitroprusside, [Fe(CN)₅NO]·2H₂O, at concentrations of 0.05, 0.1, and 0.2 µM. Growth, leaf gas exchange, and leaf anatomy analyses were performed. The experimental design was completely randomized in a 3 × 3 factorial arrangement with five replicates. The highest concentrations of Cd and SNP reduced the total dry mass and leaf and stem dry mass but increased the allocation of biomass to the roots and stem, but the leaf allocation did not change. The application of Cd and SNP promoted an increase in gas exchange and leaf area, in addition to an increase in leaf tissue thickness and stomatal density. The presence of SNP at low concentrations reduces the toxicity of Cd, but at high concentrations, this compound can generate negative effects and even toxicity in maize plants.