Antioxidative responses of cowpea cultivars to water deficit and salicylic acid treatment

Abstract

Drought stress is one of the greatest problems facing agriculture and a critical factor affecting the success or failure of agricultural activity. Application of an elicitor substance to plants, such as salicylic acid (SA), might be a strategy to induce tolerance to water deficit by acting especially on the regulation of stress-responsive mechanisms. This study aimed to evaluate the antioxidant activity of cowpea [Vigna unguiculata (L.) Walp.] seedlings as a function of water deficit and exogenous application of SA. Six cowpea cultivars were subjected to three seed treatments before sowing (WS = without soaking; SPW = soaking seeds in purified water, and SSA = soaking seeds in SA) and five water potentials induced by polyethylene glycol 6000 solution (–1.0, –0.8, –0.6, –0.4, and 0.0 MPa) during germination and early growth. Increase in the activity of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) improved the growth of cowpea seedlings under water deficit. Antioxidant activity of cowpea seedlings increased after seeds were soaked in SA, especially for cultivar BRS Itaim. BRS Itaim was more tolerant under low water potential after SA treatment and showed increase in SOD, CAT, and APX activities. Soaking seeds in SA solution (10–5 M) can be used as a strategy to induce tolerance to water deficit during seed germination and early growth of cowpea seedlings.