Sexual Differences in Growth and Physiological Characteristics of Populus cathayana under Pb Stress and Leucoagaricus sp. Colonization

Populus cathayana was used as a model species to investigate sexual differences in plant growth and physiological responses to lead (Pb) stress (0, 150 and 300 mg Pb2+ kg(-1) dry soil) with mycorrhizal (Myc) fungi colonization by Leucoagaricus sp. Results showed that high concentration of Pb stress (300 mg/kg) caused disorder in photosynthesis, inhibited plant biomass, changed antioxidant enzyme activities and increased Malondialdehyde (MDA) content in both sexes, particularly in females. Male saplings showed greater biomass, gas exchange capacity, antioxidant enzyme activity and lower MDA content when exposed to Pb stress alone and to a combination of Pb and Myc fungi treatment. Furthermore, Leucoagaricus sp. inoculation alleviated Pb toxicity in both sexes by increasing biomass accumulation, promoting gas exchange capacity, enhancing antioxidant enzyme activities and decreasing relative electrolyte leakage under low concentration (150 mg/kg) and high concentration Pb stress. Inoculation with Leucoagaricus sp. promoted Pb uptake in both sexes, and induced the sequestration of more toxic Pb in the root systems in males. Therefore, P. cathayana males associated with Leucoagaricus sp. performed best under high concentration of Pb stress and more suitably restore Pb-polluted soils than inoculated females due to the higher Pb uptake capacity and greater growth traits.