The Effects of Salicylic Acid and Ascorbic Acid on Photosynthetic Pigments and some Antioxidant Enzyme Activities in Basil (Ocimum basilicum L.) under Lead Stress

Heavy metals pollution is a major problem for the large parts of the world. Lead is a heavy metal with high toxicity that absorbed by plants mainly through the root system and in minor amounts through the leaves. After entering the cells, lead inhibits activities of many enzymes, and affects membrane structure and permeability. The objective of this research was to evaluate the effect of different concentrations of Salicylic Acid (SA) and Ascorbic Acid (AsA) on the content of photosynthetic pigments and antioxidant enzyme activities of Ocimum basilicum L. under Pb stress. Factorial experiment in a completely randomized design with three replications was conducted. Treatments were combination of 3 levels application of Pb (0, 350 & 700 mg.l-1) and 2 concentrations of SA (0, 0.1 mM) and AsA (0, 100 & 200 ppm). The results revealed that increasing lead concentration reduced chlorophyll and carotenoid content and increased activity of antioxidant enzymes (SOD, CAT). On the other hand, application SA and AsA alone and/or together, significantly increased chlorophyll content and reduced activity of antioxidant enzymes. Generally, the results of this study indicate that SA and AsA applications improved plant physiological parameters of Ocimum basilicum L.