Main Article Content
Salicylic acid (SA) acts as a signaling molecule and plays an important role in various physiological and biochemical processes in plants. The aim of the present study was to evaluate the role of SA in the enhancement of lead (Pb) tolerance in wheat (Triticum aestivum) plants. When 2–3 true leaves had appeared, treatments were applied to the plants. The treatments were as follows: (i) no addition of SA and Pb (control), (ii) 2 µM SA + 0 mM Pb, (iii) 8 µM SA + 0 mM Pb, (iv) 0 mM SA + 2 mM Pb, (v) 2 µM SA + 2 mM Pb, and (vi) 8 µM SA + 2 mM Pb. One-way analysis of variances (ANOVA) was used to compare the means, and Duncan’s multiple-range test (DMRT) was used to determine significant (P < 0.05) differences among the individual means of treatments. Exposure of Pb severely affected wheat plants by reducing plant height, fresh and dry weight, photosynthetic pigments (Chl a and b, Chl a:b) and carbonic anhydrase enzyme activity, and by enhancing Chl degradation, electrolyte leakage (EL), malondialdehyde accumulation. Also, Pb treatment increased the accumulations of proline and total soluble carbohydrates (TSC) and activities of antioxidant enzymes [superoxide dismustase (SOD), catalase (CAT), and peroxidase (POD)]. However, application of SA induced biosynthesis of pigments by suppressing Chl degradation, and EL and malondialdehyde accumulation. Furthermore, SA treatments further enhanced the production of proline and TSC, and the activities of SOD, CAT, and POD. SA directly or indirectly improved physiological processes, which helped wheat plants to overcome the oxidative damage induced by Pb toxicity. Also, this study reveals that exogenous application of SA is beneficial for plant growth and development of wheat plants by suppressing ill effects of heavy metal stress. Therefore, this study opens up the hidden role of SA in tolerance of plants to heavy metal toxicity to explore its new regulatory role and defensive mechanism at physiological and molecular levels. Also, exogenous application of SA could be beneficial for sustainable agriculture.
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