Abstract:

To investigate the effects of exogenous silicon (Si) on cadmium (Cd) absorption and accumulation in Sedum alfredii, as well as related physiological and rhizosphere mechanisms, three Si treatment levels (0, 100, 200 mg·kg⁻¹) were set up. After five months of plant growth, soil and plant-related indicators were harvested and measured. The results showed that applying exogenous Si to the soil significantly increased the activity of sucrose enzyme, acid phosphatase, and urease. In the rhizosphere soil, the concentrations of alkaline nitrogen (AN), available phosphorus (AP), and quick-release potassium (EK) also increased significantly, with dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) content showing an upward trend. The total Cd content in the soil decreased from 14.49 mg·kg⁻¹ to 11.41 mg·kg⁻¹, while the quick-release Cd content rose from 2.21 mg·kg⁻¹ to 2.69 mg·kg⁻¹. Compared to the control, applying exogenous Si increased plant height by 4.1%−8.8%, fresh weight and dry weight of above-ground parts by 34.2%−76.7% and 38.5%−76.9%, respectively. When the Si application rate reached 200 mg·kg⁻¹, chlorophyll a and b content both peaked, increasing significantly by 35.9% and 30.3% compared to the control group. The antioxidant enzyme superoxide dismutase (SOD) in the leaves was significantly higher than the control, while the activities of catalase (CAT) and peroxidase (POD) reached 2511.3, 707.2, and 3.65 U·g⁻¹, respectively. The plant chelatant (PC) content increased to 2008. 4 pg·g⁻¹, an increase of 11.3% compared to the control, while malondialdehyde (MDA) content was significantly reduced by 32.8%. Compared to the control, Si treatment significantly enhanced the plant’s ability to accumulate Cd. The above-ground Cd accumulation increased by 38.3% and 101.4%, respectively, while root Cd accumulation increased by 31.0% and 83.7%, respectively. In summary, the application of exogenous Si can promote soil nutrient release, facilitate normal growth and development of Sedum alfredii, mitigate the toxic effects of Cd, and significantly enhance its ability to absorb and accumulate Cd.

Key words: cadmium(Cd), silicon(Si), phytoremediation, Sedum alfredii, hyperaccumulator

摘要：

为探究外源硅（Si）对东南景天（Sedum alfredii Hance）吸收和富集镉（Cd）的影响及其相关生理和根际机制，设置3个Si处理水平（0、100、200 mg·kg⁻¹），植物生长5个月后收获并测定土壤和植物相关指标。结果表明，土壤施用外源Si能显著提高根际蔗糖酶、酸性磷酸酶和脲酶活性，根际土壤中碱解氮（AN）、有效磷（AP）和速效钾（EK）含量显著提高，溶解性有机碳、氮（DOC与DON）含量也呈上升趋势。土壤全Cd含量由14.49 mg·kg⁻¹降至11.41 mg·kg⁻¹，而速效Cd含量则从2.21 mg·kg⁻¹上升至2.69 mg·kg⁻¹。与对照相比，施加外源Si后，东南景天株高增加4.1%－8.8%，地上部鲜质量和干质量分别提高34.2%－76.7%和38.5%－76.9%。当Si施用量达200 mg·kg⁻¹时，叶绿素a、b含量均达最大值，较对照组显著增加35.9%和30.3%。叶片抗氧化酶超氧化物歧化酶（SOD）和对照相比显著升高，过氧化氢酶（CAT）和过氧化物酶（POD）活性分别达到2511.3、707.2和3.65 U·g⁻¹。植物螯合素（PC）含量增至2008.4 pg·g⁻¹，较对照提高11.3%，而丙二醛（MDA）含量显著降低32.8%。与对照相比，Si处理显著提高植株Cd积累能力，地上部Cd积累量分别增加38.3%和101.4%，根部Cd积累量分别提高31.0%和83.7%。综上，外源Si的施用促进土壤养分释放，促进东南景天生长发育，缓解Cd毒害，并显著提高其对Cd的吸收富集能力。

关键词: 镉, 硅, 植物修复, 东南景天, 超富集植物