Co-application of Funneliformis mosseae and salicylic acid ameliorates Pb toxicity in Salvia officinalis L. by modulating physiological responses

Heavy metals toxicity threatens food safety by disrupting plant growth and development, ultimately reducing crop yield and quality. The current study for the first time investigates a phytoremediation strategy by integrating salicylic acid and arbuscular mycorrhizal fungi to improve lead uptake and stress tolerance in Salvia officinalis L. The experiment was conducted as a factorial based on a completely randomized design with four replications. The treatments involved three levels of lead stress (0, 100, and 200 mg kg−1 of soil) in the planting soil, which was then inoculated with either 0 or 5 g kg−1 of AMF. After 1 month, salicylic acid was sprayed at either 0 or 100 µM levels. The combined application of AMF and SA effectively reduced the adverse effects of lead (Pb) stress. According to the results of variance analysis, fresh and dry weight of shoots (shoot FW and DW), protein, hydrogen peroxide, malondialdehyde, Zn content in root DW, and Fe in root DW were improved under Pb stress with simultaneous application of SA and AMF (p ≤ 0.01). The vitamin C, ascorbate peroxidase, superoxide dismutase, total phenolics, P content in shoot DW, K in root DW, and Fe in shoot DW positively responded to the treatment combinations (p ≤ 0.05). When subjected to Pb stress, plant shoots fresh and dry weights, and protein and vitamin C levels decreased. Otherwise, the concurrent application of AMF and SA improved those traits. The highest data for those traits was recorded in the simultaneous application of treatments without Pb stress, which increased by 46.82%, 48.91%, 31.62%, and 18.11% compared to the control, respectively (p ≤ 0.05). On the other hand, ascorbate peroxidase, superoxide dismutase, total phenolics, hydrogen peroxide, and malondialdehyde levels were increased under Pb stress, with additional enhancement observed with both AMF inoculation and SA spraying. In addition, P and Fe elements content in the shoot DW and K, Zn, and Fe content in the root DW of sage plants decreased under Pb stress, which was improved by the simultaneous application of SA and AMF. Moreover, the highest P content in shoots, K, and Zn in roots, and Fe in the shoot and root were recorded under conditions without Pb pollution with AMF + SA foliar treatment which were 88.84%, 44.82%, 26.31%, 26.04%, and 27.57% more than control, respectively (p ≤ 0.05). The results revealed the efficacy of the treatment combinations in combating Pb stress and even showed a reliable phytoremediation potential of the plants. Upon further evaluation, the findings will be valuable for the extension section and can be recommended for successfully cultivating sage species under the Pb-polluted soils.