Effect of cornstalk biochar on phytoremediation of Pb-contaminated soil by females and males of Populus deltoides (Salicaceae)

Soil pollution with lead (Pb) has become a serious global concern, adversely affecting the forest ecosystem. This study was conducted to investigate the effects of corn straw on the remediation efficiency of Pb-contaminated soil using Populus deltoides. Female and male P. deltoides cuttings were subjected to soil spiked with 900 mg kg(-1) Pb and amended with 5% (v/v) corn straw biochar for 90 days. Under Pb stress, the addition of biochar significantly increased the total biomass accumulation by 29% in females and 26% in males. However, without the addition of biochar, the biomass accumulation was significantly reduced by 11% in females and 3% in males under Pb stress. Females showed a higher uptake and accumulation of Pb in roots and leaves, while males accumulated more Pb in roots and stems and exhibited an increased anti-oxidative capacity. Biochar addition alleviated Pb toxicity in both male and female P. deltoides by immobilizing Pb ion in the soil, reducing Pb uptake and translocation, promoting nutrient uptake, and improving the diversity and stability of the soil bacteria community. Under Pb stress, the relative abundances of metal-resistance bacteria significantly increased, such as the abundance of Bacteroidetes in females and the abundances of Actinobacteria, Firmicutes, and Planctomycetes in males. In brief, the males under biochar addition exhibited promising potential as candidates for phytoremediation of Pb-contaminated soil. This study provides new insights into mechanisms underlying sexually differential responses to Pb stress in the presence of biochar amendment.