Glycolic acid addition enhances lead uptake and transport by Hydrangea macrophylla (Thunb.) Ser. of different plant ages

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Excessive lead in soil leads to the loss of farmland productivity, and Pb-contaminated food enters the food chain, which seriously threatens human health. Woody ornamental Hydrangea macrophylla (Thunb.) Ser is a potential remediation plant for Pb-contaminated soil; however, the efficiency of phytoremediation needs to be improved. Glycolic acid (GA) is a natural organic acid secreted by H. macrophylla roots under Pb stress. Different doses of Pb and GA were used to explore the effects of GA on the antioxidant system, soil enzyme activity, Pb accumulation, and mineral elements in H. macrophylla at different plant growth stages. The results showed that a relatively low concentration of GA increased the remediation efficiency of 1-year-old (1 yr) H. macrophylla by 39.65 % and promoted the absorption of Pb by increasing the content of K, Mn, Fe, and Zn, thereby increasing the translocation factor (TF) and bioconcentration factor (BCF). The 2-year-old (2 yrs) H. macrophylla resisted the toxicity of metals by increasing the content of MDA, and increased the content of Ca, Mg, K and Fe in order to improve the phytoremediation effect. The addition of 1.5 mM GA increased its TF and BCF by 292 % and 153 %, respectively. The translocation factor of 1 yr H. macrophylla was twice that of 2 yrs H. macrophylla , and the growth performance was better.This study provides the first comprehensive evidence that GA enhances the absorption and translocation of Pb in H. macrophylla and suggests that plants of different ages have different Pb removal efficiencies. • GA alleviated Pb-induced oxidative stress, the modulating antioxidant defense system. • GA improved the uptake of mineral nutrients in H. macrophylla under Pb stress. • GA promoted Pb accumulation in shoots and roots of H. macrophylla . • 1 yr H. macrophylla has better phytoremediation ability than 2 yrs H. macrophylla .