Salicylic acid enhances growth and cadmium-lead phytostabilization in Napier grass (Pennisetum purpureum cv. Mahasarakham).

This study evaluated the effects of salicylic acid (SA) on the growth, heavy metal accumulation, and phytoremediation performance of Napier grass (Pennisetum purpureum cv. Mahasarakham) under cadmium (Cd) and lead (Pb) stress. Salicylic acid was applied using two methods: grass-cutting soaking (S) and soaking combined with watering (SW). Both SA treatments significantly (p < 0.05) improved root and shoot growth and biomass compared with the control under both Cd-Pb co-contaminated and uncontaminated conditions. SA also enhanced leaf phytochemical composition, particularly under metal stress. Chlorophyll content increased from 0.56 in the control to 0.95 (S) and 1.03 µg mg⁻¹ (SW), while carotenoid increased from 45.7 in the control to 60.4 (S) and 62.1 µg mg⁻¹ (SW). In contrast, proline content decreased from 11.5 in the control to 10.9 (S) and 8.68 (SW), indicating reduced stress. Moreover, SA enhanced metal uptake, increasing Cd accumulation to 454.8 (S) and 279.6 mg plant⁻¹ (SW) and Pb accumulation to 427.8 (S) and 298.7 mg plant⁻¹ (SW), compared with 222.1 and 254.7 mg plant⁻¹ in their respective controls. The increased uptake resulted in greater accumulation in roots, stems, and leaves, with Napier grass exhibiting a higher bioaccumulation potential for Cd (BCF > 1) than for Pb (BCF ≤ 1). Overall, SA improved Napier grass tolerance to Cd and Pb stress by promoting plant growth, enhancing phytochemical composition, and increasing phytostabilization capacity. These findings demonstrate that SA-treated Napier grass is a promising candidate for the phytomanagement of HM-contaminated land while simultaneously serving as a high-biomass energy crop.