Xia Zhuyuan, Xue Caixin, Liu Rui, Hui Qiuling, Hu Bin, Rennenberg Heinz
Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, No. 2, Tiansheng Road, Beibei District, 400715, Chongqing, China.
Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, No. 2, Tiansheng Road, Beibei District, 400715, Chongqing, China.
Plant Physiol Biochem. 2025 Feb;219:109388. doi: 10.1016/j.plaphy.2024.109388. Epub 2024 Dec 4.
Heavy metal pollution combined with nitrogen (N) limitation is a major factor preventing revegetation of contaminated land. Woody N-fixing legumes are a natural choice for phytoremediation. However, the physiological responses of woody legumes to lead (Pb) with low N exposure are currently unknown. In the present study, a common Robinia cultivar from Northeast China, inoculated and non-inoculated with rhizobia, was exposed to -Pb or + Pb at moderate (norN) or low N application (lowN). Our results showed that without inoculation, independent of N application, Pb taken up by the roots was allocated to the shoot and inhibited photosynthesis and biomass production. In non-inoculated Robinia, Pb-mediated oxidative stress resulted in reduced HO scavenging as indicated by increased ascorbate peroxidase (APX) activity in the leaves and proline contents in the roots, independent of N application. Combined lowN∗Pb exposure significantly increased malondialdehyde (MDA) contents in roots and leaves and enhanced APX and dehydroascorbate reductase activities in leaves compared to individual Pb exposure. Rhizobia inoculation raised the abundance of nodules and promoted Pb uptake by roots. Under Pb exposure, inoculation with rhizobia reduced MDA contents, increased proline contents in leaves and roots and enhanced activity of nitrate reductase in the leaves, independent of N application. Under Pb exposure, nitrogenase activity of inoculated Robinia under low- and norN application were similar indicating that enhanced of N-fixation at lowN was counteracted by Pb exposure. These results show that inoculation of Robinia with rhizobia can alleviate Pb toxicity at combined lowN and Pb exposure by reducing oxidative stress.
重金属污染与氮（N）限制相结合是阻碍污染土地植被恢复的主要因素。木本固氮豆科植物是植物修复的自然选择。然而，目前尚不清楚木本豆科植物在低氮暴露下对铅（Pb）的生理反应。在本研究中，将一种来自中国东北的普通刺槐品种接种和未接种根瘤菌，在中等（norN）或低氮施用（lowN）条件下暴露于 -Pb 或 +Pb 环境。我们的结果表明，在未接种的情况下，无论氮施用情况如何，根系吸收的铅都会分配到地上部分，并抑制光合作用和生物量生产。在未接种的刺槐中，铅介导的氧化应激导致清除羟基自由基的能力下降，这表现为叶片中抗坏血酸过氧化物酶（APX）活性增加以及根系中脯氨酸含量增加，且与氮施用无关。与单独的铅暴露相比，低氮∗铅联合暴露显著增加了根和叶中的丙二醛（MDA）含量，并增强了叶片中 APX 和脱氢抗坏血酸还原酶的活性。接种根瘤菌增加了根瘤的数量，并促进了根系对铅的吸收。在铅暴露下，接种根瘤菌降低了 MDA 含量，增加了叶和根中的脯氨酸含量，并增强了叶片中硝酸还原酶的活性，且与氮施用无关。在铅暴露下，低氮和中等氮施用条件下接种刺槐的固氮酶活性相似，这表明低氮条件下固氮作用的增强被铅暴露所抵消。这些结果表明，接种根瘤菌可以通过降低氧化应激来减轻低氮和铅联合暴露下刺槐的铅毒性。
