Abstract：
Microbial inoculation is an important strategy to reduce the supply of heavy metals (HMs) in soil-crop systems. However, the mechanisms of microbial inoculation for the availability of HMs in soil and their accumulation/transfer in crops remain unclear. Here, the inhibitory effect of inoculation with Bacillus thuringiensis on the migration and accumulation of Pb/Cd in the soil-wheat system during the whole growth period was investigated by pot experiments. The results showed that inoculation with Bacillus thuringiensis increased soil pH and available nutrients (including carbon, nitrogen, and phosphorus), and enhanced the activities of nutrient-acquiring enzymes. Dominance analysis showed that dissolved organic matter (DOM) is the key factor affecting the availability of HMs. The content of colored spectral clusters and humification characteristics of DOM were significantly improved by inoculation, which is conducive to reducing the availability of Pb/Cd, especially during the flowering stage, the decrease was 12.8 %. Inoculation decreased Pb/Cd accumulation in the shoot and the transfer from root to shoot, with the greatest decreases at the jointing and seedling stages (27.0-34.1 % and 6.9-11.8 %), respectively. At the maturity stage, inoculation reduced the Pb/Cd accumulation in grain (12.9-14.7 %) and human health risk (4.1-13.2 %). The results of Pearson correlation analysis showed that the availability of Pb/Cd was positively correlated with the humification of DOM. Least square path model analysis showed that Bacillus thuringiensis could significantly reduce Pb/Cd accumulation in the grain and human health risks by regulating DOM spectral characteristics, the availability of HMs in soil and metals accumulation/transport in wheat at different growth stages. This study revealed the inhibition mechanism of Bacillus thuringiensis on migration of Pb/Cd in a soil-wheat system from a viewpoint of a full life cycle, which offers a valuable reference for the in-situ remediation of HM-contaminated soil and the safe production of food crops in field.
摘要：
微生物接种是减少土壤-作物系统中重金属（HM）供应的重要策略。然而,微生物接种对土壤中HMs的可用性及其在作物中的积累/转移的机制尚不清楚。这里,通过盆栽试验研究了接种苏云金芽孢杆菌对整个生育期土壤-小麦系统中Pb/Cd迁移和积累的抑制作用。结果表明,接种苏云金芽孢杆菌增加了土壤pH值和速效养分(包括碳,氮，和磷)，并增强了营养获取酶的活性。显性分析表明,溶解性有机质(DOM)是影响HMs可利用性的关键因素,接种后DOM的有色光谱簇含量和腐殖化特性均有显著提高。有利于降低Pb/Cd的可利用性,尤其是在开花阶段，跌幅为12.8%。接种减少了Pb/Cd在芽中的积累以及从根到芽的转移，拔节期和苗期下降幅度最大(27.0-34.1%和6.9-11.8%)，分别。在成熟阶段,接种降低了籽粒中Pb/Cd的积累（12.9-14.7％）和人类健康风险（4.1-13.2％）。Pearson相关分析结果表明，Pb/Cd的有效性与DOM的腐殖化程度呈正相关。最小二乘通径模型分析表明,苏云金芽孢杆菌通过调节DOM光谱特征,可以显著降低Pb/Cd在粮食中的积累和人体健康风险,不同生长阶段土壤中HMs的有效性和小麦中金属的积累/运输。本研究从全生命周期的角度揭示了苏云金芽孢杆菌对土壤-小麦系统中Pb/Cd迁移的抑制机制。为土壤的原位修复和田间粮食作物的安全生产提供了有价值的参考。
