Nitrogen (N) fertilization can improve the phytoremediation of contaminated soils. However, limited information is available on the effects and mechanisms of N availability on Cadmium (Cd) phytoextraction by dioecious plants. This study employed female and male Populus cathayana to examine sex-specific long-distance transport and cell wall Cd sequestration. Females had a greater ability to transport Cd from roots to shoots and accumulated more Cd in leaves, but had less Cd bound to the cell wall and S-containing ligands than males, irrespective of N availability. N availability affected the sex-specific ability to transport Cd and chelate it within cell walls and with S-containing ligands. Low N promoted phloem-mediated upward and downward Cd transport and total Cd accumulation in both sexes, and such effects on phloem-mediated downward Cd transport were greater than those on upward Cd transport in males. However, low-N concentration-induced Cd phloem transport was more significant in females than males. In females, low N reduced Cd accumulation in leaves via increased phloem-mediated Cd downward transport, and this Cd was subsequently sequestered in the bark and root cell walls. In contrast, for males, high N promoted xylem-mediated Cd transport to shoots and Cd sequestration in the bark but reduced phloem-mediated Cd downward transport and subsequent sequestration in root cell walls. Sex-specific genes related to root Cd transport and translocation from roots to shoots were also affected by N supply in roots. These results suggested that N availability reduced the sex-based difference in total Cd accumulation, translocation and Cd detoxification, and males showed stronger Cd tolerance than females at both N availabilities.

氮（N）施肥可以改善污染土壤的植物修复。然而，关于氮有效性对雌雄异株植物提取镉 (Cd) 的影响和机制的信息有限。本研究采用雌性和雄性青杨检查性别特异性长距离运输和细胞壁镉封存。雌性将镉从根部转运到芽的能力更强，并且在叶子中积累了更多的镉，但与雄性相比，与细胞壁和含硫配体结合的镉较少，无论氮的利用率如何。氮的可用性影响了转运镉并将其螯合在细胞壁内以及与含硫配体的性别特异性能力。低氮促进了两性中韧皮部介导的向上和向下的镉转运以及总镉积累，并且这种对韧皮部介导的向下的镉转运的影响大于对雄性的向上的镉转运的影响。然而，低氮浓度诱导的镉韧皮部转运在雌性中比雄性更显着。在雌性中，低氮通过增加韧皮部介导的镉向下运输减少了叶片中镉的积累，这种镉随后被隔离在树皮和根细胞壁中。相反，对于雄性来说，高氮促进木质部介导的镉向芽的转运和树皮中镉的封存，但减少韧皮部介导的镉向下运输和随后在根细胞壁中的封存。与根部镉转运和从根部到芽的​​易位相关的性别特异性基因也受到根部氮供应的影响。这些结果表明，氮利用率降低了总镉积累、易位和镉解毒方面的性别差异，并且在两种氮利用率下，雄性都比雌性表现出更强的镉耐受性。高氮促进木质部介导的镉向芽的转运和树皮中镉的固存，但减少韧皮部介导的镉向下转运和随后在根细胞壁中的固存。与根部镉转运和从根部到芽的​​易位相关的性别特异性基因也受到根部氮供应的影响。这些结果表明，氮利用率降低了总镉积累、易位和镉解毒方面的性别差异，并且在两种氮利用率下，雄性都比雌性表现出更强的镉耐受性。高氮促进木质部介导的镉向芽的转运和树皮中镉的固存，但减少韧皮部介导的镉向下转运和随后在根细胞壁中的固存。与根部镉转运和从根部到芽的​​易位相关的性别特异性基因也受到根部氮供应的影响。这些结果表明，氮利用率降低了总镉积累、易位和镉解毒方面的性别差异，并且在两种氮利用率下，雄性都比雌性表现出更强的镉耐受性。