Comparative effects of salicylic and giberellic acid on lipid peroxidation and antioxidant potentials of three cultivars of Vigna unguiculata (L.) Walp under heavy metal toxicity

Cowpea is a commonest and affordable legume widely consumed in developing nation of the world. Salicylic (SA) and Gibberellic (GA) acids serve to play prominent roles in induction of growth and development in cowpea. However, heavy metal such as arsenic is one of the major pollutant commonly encountered and its exposure to plant often result in alteration in physiological and biochemical functions. Therefore the aim of this work was to examine the effects of Salicylic and Gibberellic acid on lipid peroxidation and antioxidant potentials of three cultivars of Vigna unguiculata under heavy metal toxicity. Seeds of three cowpea cultivars (Ife Brown, ITOK-768-18and ART 98-12) were sorted and each of the three cultivars were soaked in SA [0 control, (75, 150) mg/L} and GA [0 control, (75, 150) mg/L} respectively. The seeds (n=5) were planted in a completely randomised design in pots of soil containing each of 0, 250 and 500mg/L sodium arsenate. Vitamin C, otal flavonoid, phenolic, lipid peroxidation, superoxide dismutase, peroxidase, catalase activities in leaves were determined on day 90 using spectrophotometry The results show that in comparing treatment with the control among the three cultivars, superoxide dismutase, peroxidase and catalase, vitamin C, total flavonoid and phenolic were increased by (3, 4, 2, 12, 4 and 3 folds respectively), in Ife brown; (2, 5, 12, 12, 5 and 3 folds respectively), in ART 98-12; (4, 3, 14, 5 and 4 folds respectively), in ITOK-768-18 in the leaves of 250mg/L sodium arsenate-treated soil with SA (150mg/L). Lipid peroxidation were reduced by (5 and 3 folds respectively), in Ife brown and ITOK-768-18 in 250mg/L sodium arsenate-treated soil with SA (150mg/L) but was reduced by 3 folds in 250mg/L sodium arsenate-treated soil with SA (75mg/L) for ART98-12. Salicylic and gibberellic acids therefore reduced lipid peroxidation, enhanced antioxidant potentials of Vigna unguiculata to increase tolerance and promote growth during heavy metal toxicity.