Synergistic mitigation of lead [Pb(II)] stress in Triticum aestivum L. by heavy metal-tolerant plant growth-promoting (HMT-PGP) microbes and N-acetylcysteine (NAC).

Synergistic application of N-acetylcysteine (NAC) and heavy metal-tolerant plant growth promoting (HMT-PGP)microbial consortia enhances Pb(II) phytostabilization and stress tolerance in Triticum aestivum L. by improvinggrowth, redox balance, and limiting metal uptake. This study emphasizes a synergistic approach using N-acetylcysteine (NAC) and heavy metal-tolerant plant growth-promoting (HMT-PGP) microbes to enhance lead [Pb(II)] phytostabilization in Triticum aestivum L. under hydroponic conditions. Though microbial consortia (MC) and NAC individually improved seed germination and viability, along with physiological and biochemical parameters under Pb(II) stress, the effects were more pronounced in the combined treatment (MC and NAC). In the combined treatment, seed germination, viability, amylase, and protease activities were found to increase by 20.7, 27.7, 21.4, and 10.82%, respectively, compared to the Pb(II)-stressed control (T1). Furthermore, combined treatment (NAC + MC) enhanced plant root, shoot length, biomass, and total chlorophyll by 46.9, 34.1, 21.6, and 45.6%, respectively, while total carotenoids and chlorophyll-carotenoid ratio decreased by 14.1 and 43.8%, respectively. Treatment with MC and NAC protected the plants against Pb(II) toxicity, as evidenced by significant declines in oxidative stress markers (hydrogen peroxide, malondialdehyde, proline) and in antioxidant enzyme activity. MC and NAC, individually and synergistically, restricted the Pb(II) uptake and accumulation in plants, thus leading to a significant reduction in bioconcentration (BCF) and translocation factor (TF) values. The BCF values for Pb(II) in the plants were 0.74 (untreated), 0.61 (MC), 0.67(NAC), and 0.58 (MC + NAC); while those for TF were 0.16, 0.11, 0.12, and 0.095, respectively. The treatments also promoted colonization of root endophytes. The findings suggest that MC and NAC, independently and synergistically, not only maintain redox homeostasis but also restrict Pb(II) entry in the plant. Therefore, it offers a novel approach for enhancing T. aestivum tolerance to Pb(II)-induced stress, promising avenues for sustainable agricultural practices and environmental remediation.