Changes in antioxidant enzymes activity and physiological traits by exogenous salicylic acid in basil (Ocimum basilicum) under Pb stress

Salicylic acid (SA) is a key molecule that alleviates abiotic stress in many plant species. In this study, the role of SA was examined to moderate lead (Pb) toxicity in the basil (Ocimum basilicum). The experimental design was a randomized complete block design with 4 levels of PbNO3; 0 (control), 100, 200 and 300 mg kg-1 of soil as the first factor, and the foliar application of SA at 3 levels of 0, 50 and 100 mL L-1 comprised second factor that were applied with four repetitions. The experiment was conducted during 2013 at research greenhouse of the Zabol University. Addition of Pb at a rate of 300 mg.kg-1 significantly reduced the carotenoids by 45.5 percent and organic acids by 49.3 percent, while it caused an increase in anthocyanins, flavonoids, electrolyte leakage and antioxidant enzymes, including lipoxygenase and glutathione peroxidase. In addition, SA spraying had a significant influence on all traits. In this study, the interaction effects between SA and Pb was significant on carotenoids, anthocyanins, flavonoids, electrolyte leakage, organic acid, and lipoxygenase and glutathione peroxidase, and play a moderating role and reduce the harmful effects of Pbtoxicity. The results of this experiment suggested that the application of SA in basil caused a reduction in oxidative damage originated by Pb toxicity and induce the synthesis of photosynthetic pigments, such as carotenoids.