Luo Xu-Feng, Yi Xuan-Tao, Wang De-Zheng, Wang Jiang-Yao, Zeng Peng, Zhou Hang, Gu Jiao-Feng, Liao Bo-Han, Li Hao
College of Life and Environmental Sciences, Central South University of Forestry and Technology, No. 498, Shaoshan South Road, Tianxin District, Changsha, Hunan Province 410004, China.
College of Environment and Ecology, No. 1, Nongda Road, Furong District, Hunan Agricultural University, Changsha, Hunan Province 410128, China.
Tree Physiol. 2025 Mar 3;45(3). doi: 10.1093/treephys/tpaf015.
Woody plants have received considerable attention for the phytoremediation of heavy metal-contaminated soil. This study aimed to investigate the changes in antioxidant enzyme activity, macroelement uptake and microstructure of the woody plant Robinia pseudoacacia (black locust) for the phytoremediation of cadmium (Cd) and lead (Pb) co-contaminated soil based on dynamic sampling. The results show that black locust demonstrates strong tolerance in Cd and Pb co-contaminated soil. After 30-120 days of cultivation, the activities of superoxide dismutase, peroxidase and the macroelement (potassium [K] and calcium [Ca]) content in plant leaves significantly declined in response to Cd and Pb. However, after 160 d of cultivation, the antioxidant enzyme activities, chlorophyll, sulfhydryl and soluble protein contents, as well as Ca and magnesium content in plant leaves were returned to normal levels under the 40 mg kg-1 Cd and 1000 mg kg-1 Pb contaminated soil (CdPb3). Meanwhile, K content in plant leaves under the CdPb3 treatment was significantly (P < 0.05) increased by 68.9% compared with the control. Cadmium and Pb were primarily accumulated in black locust roots. Scanning electron microscope analysis indicated that the sieve tubes in the roots and stems of plant might block the transport of Cd and Pb. Transmission electron microscope analysis indicated that the number and volume of osmiophilic particles in plant leaves were increased and the cell walls were thickened in response to Cd and Pb stress. Path analysis further indicated that the growth of plant was related to macroelements uptake and physiological change (photosynthesis, antioxidant enzyme activity and chelation). Thus, black locust could effectively regulate the antioxidant defense system, macroelement absorption and microstructure to enhance plant tolerance to Cd and Pb stress. Moreover, black locust could maintain the normal urease, acid phosphatase and sucrase activities in the Cd and Pb co-contaminated soil. These findings suggest that black locust could be considered as a useful woody plant for the phytostabilization in Cd- and Pb-contaminated soil.
木本植物在重金属污染土壤的植物修复方面受到了广泛关注。本研究旨在基于动态采样，研究木本植物刺槐对镉（Cd）和铅（Pb）共污染土壤进行植物修复时，其抗氧化酶活性、大量元素吸收及微观结构的变化。结果表明，刺槐在Cd和Pb共污染土壤中表现出较强的耐受性。培养30 - 120天后，超氧化物歧化酶、过氧化物酶的活性以及植物叶片中大量元素（钾[K]和钙[Ca]）的含量因Cd和Pb而显著下降。然而，培养160天后，在40 mg kg-1 Cd和1000 mg kg-1 Pb污染土壤（CdPb3）条件下，植物叶片中的抗氧化酶活性、叶绿素、巯基和可溶性蛋白含量以及Ca和镁含量恢复到正常水平。同时，CdPb3处理下植物叶片中的K含量与对照相比显著（P < 0.05）增加了68.9%。Cd和Pb主要积累在刺槐根部。扫描电子显微镜分析表明，植物根和茎中的筛管可能会阻碍Cd和Pb的运输。透射电子显微镜分析表明，响应Cd和Pb胁迫，植物叶片中嗜锇颗粒的数量和体积增加，细胞壁增厚。通径分析进一步表明，植物的生长与大量元素吸收和生理变化（光合作用、抗氧化酶活性和螯合作用）有关。因此，刺槐可以有效地调节抗氧化防御系统、大量元素吸收和微观结构，以增强植物对Cd和Pb胁迫的耐受性。此外，刺槐可以在Cd和Pb共污染土壤中维持正常的脲酶、酸性磷酸酶和蔗糖酶活性。这些发现表明，刺槐可被视为Cd和Pb污染土壤植物稳定修复的一种有用木本植物。
