Abstract:

Hyperaccumulator remediation is one of the most studied and promising technologies for the treatment of heavy metal pollution in soil. However, when hyperaccumulators are used to remediate soil heavy metal pollution, the significant decrease in biomass has become a difficulty in its large-scale application. Taking Perilla frutescens as the material, the response of bamboo vinegar (BV) to Perilla frutescens growth and Cd enrichment under different Cd stress levels was studied by a hydroponics experiment, and the mitigation effect of BV on Cd toxicity of Perilla frutescens and the feasibility on improving phytoremediation efficiency were evaluated. The results showed that at 4 mg·L^-1 and 8 mg·L^-1 Cd concentrations, BV significantly increased the total dry weight (36.8% and 20.6%), phenolic acid (93.6% and 30.9%), flavonoid mass fraction (80.0% and 31.9%), and rhizo-phenolic acid mass fraction (25.3% and 31.2%) of Perilla frutescens. The root flavonoid mass fraction increased by 34.7% at 4 mg·L^-1 Cd concentration, but had no significant difference at 8 mg·L^-1 Cd concentration. Under BV treatment, the activities of POD in roots increased by 64.2% and 65.1% at 4 mg·L^-1 and 8 mg·L^-1 Cd treatments, respectively. Leaves and root APX enzyme activities were increased by 414.1% and 76.0%, respectively, under the treatment of 8 mg·L^-1 Cd. In general, under 4 mg·L^-1 Cd concentration and 8 mg·L^-1 Cd concentration, the application of BV significantly increased the Cd mass fraction in the aboveground (16.5% and 21.4%) and underground (14.0% and 62.8%) parts of the plant, and the Cd accumulation in the plant was improved by 69.3% and 55.7%, respectively. Principal component analysis showed that spraying BV could improve plant enzymatic and non-enzymatic antioxidant systems and increase plants’ environmental adaptability under the 4 mg·L^-1 Cd treatment, but had little effect on physiological damage under the 8 mg·L^-1 Cd treatment. Correlation analysis showed that there was a significant positive correlation (P<0.05) between root cadmium content and root phenolic acid. In conclusion, BV increased the activities of POD and APX of Perilla frutescens, which can alleviate the damage of Cd to it, as well as improve plant growth under Cd stress, the content of flavonoids and phenolic acids, and the enrichment efficiency of Cd. The results can furnish a theoretical foundation for the promotion of phytoremediation technologies that the remediate Cd-polluted soils.

Key words: cadmium, bamboo vinegar, phytoremediation, antioxidant enzyme, phenolic acid

摘要：

超富集植物修复是目前研究较多且具有良好发展前景的重金属污染土壤治理技术。然而，采用超富集植物对重金属污染土壤进行修复时，生物量大幅下降成为其难以大面积推广应用的难点。以超富集植物紫苏（Perilla frutescens）为材料，采用水培实验，研究竹醋液（BV）对不同Cd胁迫水平下紫苏生长以及Cd富集变化的响应，评估了BV对紫苏镉毒的缓解效应以及提高植物修复效率的可行性。结果表明，在Cd质量浓度为4 mg·L^-1和8 mg·L^-1的处理下，外施BV显著增加了紫苏的总干重（36.8%和20.6%），叶酚酸（93.6%和30.9%）和类黄酮质量分数（80.0%和31.9%），以及根酚酸质量分数（25.3%和31.2%）。根类黄酮质量分数在4 mg·L^-1 Cd处理下增加了34.7%，而在8 mg·L^-1 Cd处理下无显著差异；外施BV处理下，根系POD酶活性在4 mg·L^-1和8 mg·L^-1 Cd处理下分别增加了64.2%和65.1%。叶和根系APX酶活性在8 mg·L^-1 Cd处理下分别提高414.1%和76.0%。总体上，在4 mg·L^-1和8 mg·L^-1 Cd质量浓度处理下，外施BV显著提高了植株地上部（16.5%和21.4%）和地下部（14.0%和62.8%）Cd质量分数，使植株Cd富集量分别提高了69.3%和55.7%。主成分分析表明，喷施BV可以改善植物酶与非酶抗氧化系统，增加了4 mg·L^-1 Cd处理下植物的环境适应性，而对8 mg·L^-1 Cd处理下植物的生理损伤影响较小。相关性分析表明，根系镉含量与根系酚酸呈显著正相关（P<0.05）。综上所述，BV通过提高紫苏POD和APX酶活性，增加类黄酮和酚酸类物质含量，缓解Cd对紫苏的损伤，促进Cd胁迫下植物生长，从而提高植物Cd富集效率。研究结果可为植物修复Cd污染土壤治理技术的推广提供理论基础。

关键词: 镉, 竹醋液, 植物修复, 抗氧化酶, 酚酸