假单胞菌TCd-1对不同镉耐性水稻品种镉吸收及根际土壤酶活性与镉形态的影响

Effects of Pseudomonas TCd-1 inoculation on Cd uptake, rhizosphere soils enzyme activities and Cd bioavailability in rice (Oryza sativa) varieties with different Cd tolerance

  • 摘要: 为探究假单胞菌TCd-1降低水稻镉吸收的根际生态机制, 以高镉耐性水稻品种‘特优671’和低镉耐性水稻品种‘百香139’为材料, 通过盆栽土培试验, 研究了接种TCd-1菌株对10 mg∙kg−1镉处理水稻镉吸收、根际土壤镉形态及酶活性的影响。结果表明: 接种菌株后高、低镉耐性水稻品种各部位的镉含量显著降低(P<0.05), 镉富集系数分别降低35.14%和47.79%, 转移系数无显著变化; 根际土壤可交换态镉含量分别显著降低15.89%和23.81% (P<0.05) , 铁锰氧化结合态镉含量显著提高39.58%和28.81% (P<0.05), 有机态镉含量显著提高36.11%和25.00% (P<0.05); 低镉耐性水稻品种根际土壤酸性磷酸酶、脲酶、蔗糖酶、纤维素酶和过氧化氢酶活性依次提高26.74%、12.07%、62.50%、81.17%和5.13%, 多酚氧化酶活性降低12.40%, 高镉耐性水稻的酸性磷酸酶、脲酶、蔗糖酶、纤维素酶和多酚氧化酶活性依次降低7.19%、9.39%、25.53%、16.20%和11.44%, 过氧化氢酶活性提高5.13%。可见, 假单胞菌TCd-1主要通过降低根际土壤镉的生物有效性、恢复土壤酶活性, 进而提高水稻耐镉能力并抑制水稻对镉的吸收与积累, 对高、低不同镉耐性水稻品种, 接种TCd-1菌株后其镉富集特性、根际土壤酶活性及不同镉形态含量占比均表现出显著差异。

     

    Abstract: Heavy metal contamination in rice (Oryza sativa) is a serious problem. Microbial remediation is a promising technique to reduce Cd accumulation in rice. To explore the rhizosphere-associated ecological mechanism of Pseudomonas TCd-1-induced reduction of Cd uptake in rice, two rice varieties, high Cd-tolerant variety ‘Teyou 671’ and low Cd-tolerant variety ‘Baixiang 139’, were used. A set of soil culture pots treated with 10 mg∙kg−1 Cd were employed to evaluate the effects of Pseudomonas TCd-1 inoculation on rice Cd uptake and enzymes activities in rhizosphere soils. The results showed that the Cd content in different parts of both the high and low Cd-tolerant rice varieties significantly decreased (P<0.05) after inoculation of Pseudomonas TCd-1, and the bioconcentration factor (BCF) of Cd decreased by 35.14% and 47.79% (P<0.05), respectively. However, no significant changes were found in the translocation factor (TF). Meanwhile, in rhizosphere soils of the high and low Cd-tolerant rice varieties, the content of exchangeable Cd decreased by 15.89% and 23.81% (P<0.05), Fe-Mn oxide bound Cd increased by 39.58% and 28.81% (P<0.05), and organic matter Cd increased by 36.11% and 25.00% (P<0.05), respectively. In addition, the activities of acid phosphatase, urease, saccharase, cellulase, and catalase significantly increased by 26.74%, 12.07%, 62.50%, 81.17%, and 5.13%, respectively; while the polyphenol oxidase activity decreased by 12.40% in the rhizosphere soils of low Cd-tolerant rice variety. In rhizosphere soils of high Cd-tolerant rice variety, the activities of acid phosphatase, urease, sucrase, cellulase, and polyphenol oxidase decreased by 7.19%, 9.39%, 25.53%, 16.20%, and 11.44%, respectively; while catalase activity increased by 5.13%. There were significant differences in enrichment characteristics, rhizosphere soil enzymes activities, and the proportions of different chemical forms of Cd in rhizosphere soils of different Cd-tolerant rice varieties after inoculation with the TCd-1 strain. The results indicated that inoculation with the strain may partly remediate the changes in soil enzymes activities caused by Cd pollution. In conclusion, Pseudomonas TCd-1 can improve Cd tolerance and inhibit Cd uptake and accumulation in rice, mainly by reducing the bioavailability of soil Cd and restoring the changes in soil enzymes activities caused by Cd pollution.

     

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