不同氮肥水平下玉米与龙葵竞争吸收镉的差异性研究

【目的】 研究不同氮肥用量处理对玉米镉 (Cd) 积累的影响及其生理响应机制，为今后利用玉米–龙葵间作模式进行植物修复时合理使用氮肥、减少修复成本及环境污染奠定基础。 【方法】 以Cd超积累植物龙葵 (Solanum nigrum L.) 与玉米为供试材料，取Cd污染浓度为2.79 mg/kg的供试土壤，采用温室盆栽试验，设置玉米单作及玉米、龙葵竞争模式下3个不同氮肥用量处理，分别为不施肥、N 0.1 g/kg、N 0.2 g/kg，研究施氮量对玉米、龙葵的生长以及各器官吸收积累Cd的影响。 【结果】 施用氮肥能提高玉米和龙葵各器官的生物量，且随着施氮量的增加龙葵和玉米的生物量均显著性增加，高施氮量处理下龙葵根、茎、叶、籽粒生物量增量最大，分别增加了47.2%、51.0%、25.3%、63.2%；玉米根、茎、叶、籽粒生物量分别增加了35.5%、17.0%、76.2%、112%。不同氮肥用量处理下，龙葵各器官中Cd含量显著性增加，同时与其竞争的玉米各器官Cd含量显著性下降。玉米与龙葵竞争模式下高施氮量处理的龙葵根、茎、叶、籽粒中Cd含量分别增加了23.2%、41.2%、12.3%、45.3%；玉米根、茎、叶、籽粒中Cd含量分别下降了49.2%、38.0%、42.8%、19.5%。高施氮量处理下，龙葵各器官Cd累积量显著性增加，根、茎、叶、籽粒中Cd累积量分别增加85.6%、88.4%、131%、159%；同时玉米各器官Cd累积量显著性降低，茎、叶、籽粒中Cd累积量分别下降12.2%、34.8%、79.5%。高施氮量处理下，玉米与龙葵竞争模式下龙葵富集系数增加113%，转运系数增加15.1%；玉米的富集系数降低25.7%，转运系数降低15.2%。玉米与龙葵竞争模式下，随着施氮量的增加，龙葵对Cd的吸收转运能力增强，玉米对Cd的吸收转运能力受到抑制。因此，Cd污染土壤中，通过玉米–龙葵间作处理并适当提高施氮量，能够促进龙葵的生长和地上部Cd的积累能力。这一研究结果旨在为修复污染土壤，提高修复效率以及保证农产品质量安全提供理论依据。 【结论】 玉米与龙葵竞争模式下，0.2 g/kg的施氮量能够促进龙葵对Cd的吸收转运，降低Cd在玉米各器官的累积，并提高Cd污染土壤的修复效率，达到边生产边修复的目的。

Difference of the Cadmium uptake by competition between Zea mays L. and Solanum nigrum L. under different nitrogen fertilizer levels

【Objectives】 Investigate the effects of different nitrogen fertilizer application rates on cadmium (Cd) accumulation in maize and its physiological response mechanism. This research aims to lay the foundation for the reasonable use of nitrogen fertilizer, reduce the cost of restoration and environmental pollution in future plant remediation by using Zea mays L. (maize) and Solanum nigrum L. intercropping system. 【Methods】 The Cd-hyperaccumulator S. nigrum and maize were used as test materilas, soil with Cd concentration of 2.79 mg/kg, the pot experiment was conducted to study the three treatments of different nitrogen fertilizers rates, the treatments were monoculture and non-fertilizer, N 0.1 g/kg, and N 0.2 g/kg in competition mode, and study the effects of the nitrogen fertilizer application rate on the growth and Cd accumulation in various organs of maize and S. nigrum. 【Results】 The research showed that the application of nitrogen fertilizer could increase the biomass of various organs of maize and S. nigrum, the biomass of S. nigrum and maize increased significantly with the increase of nitrogen application rate. The biomass increment of the root, stem, leaf and grain was the largest in the high application rate of nitrogen fertilizer, which increased by 47.2%, 51.0%, 25.3% and 63.2% for S.nigrum, respectively. The biomass of root, stem, leaf and grain of maize increased by 35.5%, 17.0%, 76.2% and 112%, respectively. Under different application rates of nitrogen fertilizer treatments, the concentration of Cd in the organs of S. nigrum increased significantly, while the concentration of Cd in the organs of maize was decreased significantly. Under maize and S. nigrum competition mode, with the high application rate of nitrogen fertilizer treatment, the concentration of Cd in root, stem, leaf and grain of S. nigrum increased by 23.2%, 41.2%, 12.3% and 45.3%, respectively. The Cd concentration in root, stem, leaf and grain of maize decreased by 49.2%, 38.0%, 42.8% and 19.5%, respectively. Under high application rate of nitrogen fertilizer treatment, Cd accumulation in organs of S. nigrum increased significantly, and Cd accumulation in root, stem, leaf and grain increased by 85.6%, 88.4%, 131% and 159%, respectively; the Cd accumulation in organs of maize was significantly reduced, and the Cd accumulation in stem, leaf and grain decreased by 12.2%, 34.8% and 79.5%, respectively. Under high application rate of nitrogen fertilizer, the enrichment coefficient of S. nigrum increased by 113% and the translocation coefficient increased by 15.1% under the competition mode between maize and S. nigrum; the enrichment coefficient of maize decreased by 25.7%, and the transport coefficient decreased by 15.2%. Under the competition mode between maize and S. nigrum, as the amount of nitrogen fertilizer increased, the Cd uptake and translocation of S. nigrum increased, and the Cd absorption and transportion of maize would be inhibited. Therefore, in the Cd contaminated soil, through the maize and S. nigrum intercropping treatment and the appropriate application of nitrogen fertilizer, the growth of S. nigrum and the Cd accumulation of shoots could be increased. The results of this study were intended to provide a theoretical basis for remediation of contaminated soil, improvement of remediation efficiency, and assurance of quality and safety of agricultural products. 【Conclusions】 Under maize and S. nigrum competition mode, the high nitrogen application rate of N 0.2 g/kg could promote the uptake and translocation of Cd by hyperaccumulator S. nigrum, reduce the accumulation of Cd in various organs of maize, and improve the remediation efficiency of Cd contaminated soil, thus achieve the goal of the production and remediation at the same time.