Lead remediation capabilities of three shrub willow clones and the cellular, physiological and molecular responses of Salix integra to Lead stress

The production of lead (Pb) -acid batteries and the emission of vehicle exhaust have been increasingly contributing to soil Pb(Ⅱ) pollution in recent years. Pb(Ⅱ) is a highly stable and hazardous heavy metal. Phytoremediation technology has garnered widespread attention due to its permanent and significant remediation effects. This study further analyzes biomass and Pb(Ⅱ) content data from different clones of 3 shrub willow species under 3 concentrations of Pb(Ⅱ) treatment. The results indicate that all 3 shrub willows exhibit strong Pb(Ⅱ) remediation capabilities, with variations observed among different clones. Using the Salix integra clone P336 as experimental material, macroscopic (plant phenotype) and microscopic (root subcellular structure) symptoms of poisoning under Pb(Ⅱ) stress were observed. Symptoms such as plant wilting and leaf yellowing began to appear after 3 days of treatment with 0.3 mM Pb(Ⅱ). Cytological observations revealed that after Pb(Ⅱ) absorption, it primarily accumulated in relatively inactive cellular components such as the cell wall and vacuoles of root cells. Further research found that Glutathione S-transferases plays the most critical role in Pb(Ⅱ) tolerance in S. integra, with its activity being the most important indicator affecting Pb(Ⅱ) tolerance. By examining the expression levels of genes related to reduced glutathione synthesis, transformation, and chelation, it was found that they all showed significant positive responses to Pb(Ⅱ) stress. This study not only offers superior plant materials for research on Pb(Ⅱ) remediation using woody species, but also preliminarily reveals the cellular and molecular response mechanisms of willows to Pb(Ⅱ) stress.