ABSTRACT

Anthropic activities and agricultural practices have increased the rate of pollutants in ecosystems. Consequently, this can alter soil chemical properties, biological functioning, and fertility. Our work aimed to evaluate the impact of nickel (Ni) contamination on rhizospheric soil’s physico-chemical properties and microbiological activities in the presence of alfalfa plants. For this purpose, five concentrations of Ni (0, 50, 150, 250, and 500 mg.kg⁻¹) were applied to Tunisian agricultural soils cultured with Medicago sativa. At the end of the experiment, the physico-chemical properties of these soils and the Ni uptake by alfalfa plants were analyzed. Additionally, soil enzyme activities were assessed. Finally, the microbial biomass and functional diversity of microbial communities were determined using SIR (Substrate-induced respiration) and Biolog Ecoplates™ techniques, respectively. The results revealed that Ni accumulation was dose-dependent, with a significant amount of Ni being translocated from the roots to the shoots. With respect to the physico-chemical properties of soil, the most important Ni concentration led to the lowest organic matter content and cation-exchange capacity (CEC). Our data also showed a decrease in soil enzyme activities following Ni contamination. However, a crucial increase on microbial biomass of soils was revealed with the high Ni contamination. Moreover, the microbial functional diversity index and substrate utilization pattern were observed to increase in soils exposed to the most potent Ni concentrations. Our data provided evidence regarding the apparent toxicity of Ni and the fact that enzymatic activities and microbial biomass could be exploited as Ni-stress bioindicators.

摘要

人类活动和农业实践增加了生态系统中污染物的比率。因此，这可以改变土壤的化学性质，生物学功能和肥力。我们的工作旨在评估苜蓿植物存在下镍（Ni）污染对根际土壤理化性质和微生物活性的影响。为此，将五种浓度的镍（0、50、150、250和500 mg.kg ^-1）施用于用紫花苜蓿栽培的突尼斯农业土壤。在实验结束时，分析了这些土壤的物理化学性质以及苜蓿植物对镍的吸收。另外，评估土壤酶活性。最后，分别使用SIR（底物诱导的呼吸）和Biolog Ecoplates™技术确定了微生物群落的微生物生物量和功能多样性。结果表明，镍的积累是剂量依赖性的，大量的镍从根部转移到芽。关于土壤的理化性质，最重要的镍浓度导致最低的有机质含量和阳离子交换容量（CEC）。我们的数据还表明，镍污染后土壤酶活性下降。然而，高镍污染表明土壤微生物量的关键增加。此外，在暴露于最有效的Ni浓度的土壤中，观察到微生物功能多样性指数和底物利用模式增加。我们的数据提供了有关镍的明显毒性以及酶活性和微生物生物量可以用作镍胁迫生物指示剂这一事实的证据。