Andromonoecious individuals of <i>Populus schneideri</i> respond more sensitively to N-deficiency and Cd pollution than males and females

Species from the genus Salicaceae are typically dioecious, yet a complex sex structure might be observed in natural populations. So far, the divergence in environmental adaptability between monoecious (either andromonoecious or gynomonoecious) and dioecious individuals (males and females) has been little studied. We investigated differences in growth, photosynthesis, nutrient-use efficiency, cadmium (Cd) accumulation and allocation among male, female and andromonoecious individuals of Populus schneideri (Rehder) N. Chao under nitrogen (N)-deficiency, Cd pollution and their combination. Compared with the control, N-deficiency alone and the combined stress reduced growth, photosynthesis, dry mass accumulation, photosynthetic N-use efficiency and phosphorus-use efficiency in all sexes, while inhibiting ascorbate peroxidase and glutathione reductase activities and inducing membrane lipid peroxidation. Males were the least affected by N-deficiency, followed by females, while andromonoecious plants were the most severely impacted. Under Cd addition treatments, the youngest (the first and second order) roots were the main organs of Cd accumulation across all sexes. Andromonoecious plants had the highest Cd content in leaves, while it was the lowest in males. Nitrogen-deficiency decreased Cd bioconcentration factor in female and andromonoecious plants, but not in males. Taken together, these results indicate that females and, in particular, andromonoecious plants are more negatively affected by N-deficiency and the combined stress, whereas males exhibit a greater adaptability. We argue that divergent responses of andromonoecious plants need to be considered in predicting the performance of ecosystems with complex sex structure.