State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, 712100, China; CAS Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xian, 710061, China.
Institute of Soil and Water Conservation, Chinese Academy of Sciences, Ministry of Water Resources, Yangling, 712100, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Ecotoxicol Environ Saf. 2019 Oct 30;182:109459. doi: 10.1016/j.ecoenv.2019.109459. Epub 2019 Jul 22.
The utilization of forages grown on metal-contaminated soil can increase the risk of heavy metals entering the food chain and affecting human health because of elevated toxic metal concentrations. Meanwhile, hydrogen sulfide (HS) and nitric oxide (NO) as signaling molecules are known to promote plant growth in metal-contaminated soils. However, the regulatory mechanisms of such molecules in plant physiology and soil biochemistry have not been well-documented. Hence, we investigate the role of the exogenous application of HS and NO on alfalfa growth in lead/cadmium (Pb/Cd)-contaminated soil. Our results indicate that the signaling molecules increase the alfalfa chlorophyll and biomass content and improve alfalfa growth. Further, HS and NO reduce the translocation and bioconcentration factors of Pb and Cd, potentially reducing the risk of heavy metals entering the food chain. These signaling molecules reduce metal-induced oxidative damage to alfalfa by mitigating reactive oxygen species accumulation and increasing antioxidant enzyme activities. Their exogenous application increases soil enzymatic activities, particularly of catalase and polyphenol oxidase, without significantly changing the composition and structure of rhizosphere bacterial communities. Interestingly, HS addition enriches the abundance of plant-growth-promoting rhizobacteria in soil, including Nocardioides, Rhizobium, and Glycomyces. HS is more effective than NO in improving alfalfa growth and reducing heavy-metal contamination of the food chain. These results provide new insights into the exogenous application of signaling molecules in alleviating metal-induced phytotoxicity, including an efficient strategy for the safe use of forages.
利用生长在受金属污染土壤上的饲料会增加重金属进入食物链并影响人类健康的风险，因为有毒金属浓度升高。同时，已知氢硫化物 (HS) 和一氧化氮 (NO) 作为信号分子可以促进受金属污染土壤中的植物生长。然而，这些分子在植物生理学和土壤生物化学中的调控机制尚未得到充分记录。因此，我们研究了外源 HS 和 NO 对苜蓿在铅/镉 (Pb/Cd) 污染土壤中生长的作用。我们的结果表明，这些信号分子增加了苜蓿的叶绿素和生物量含量，改善了苜蓿的生长。此外，HS 和 NO 降低了 Pb 和 Cd 的迁移和生物浓缩系数，可能降低重金属进入食物链的风险。这些信号分子通过减轻活性氧积累和增加抗氧化酶活性来减轻金属对苜蓿的氧化损伤。它们的外源应用增加了土壤酶活性，特别是过氧化氢酶和多酚氧化酶的活性，而不会显著改变根际细菌群落的组成和结构。有趣的是，HS 的添加增加了土壤中促进植物生长的根际细菌的丰度，包括诺卡氏菌、根瘤菌和糖单胞菌。HS 比 NO 更有效地改善苜蓿的生长和降低食物链中的重金属污染。这些结果为缓解金属诱导的植物毒性中外源应用信号分子提供了新的见解，包括安全使用饲料的有效策略。
