施用氮肥对烟草镉积累及其根际细菌群落的影响

Effects of nitrogen fertilizer application on cadmium accumulation and rhizosphere bacterial community of tobacco

【目的】虽然烟草有望成为一种理想的镉污染土壤修复植物,但氮肥如何影响烟草镉积累及其机制需进一步明确。【方法】采用室内试验,比较了施用3种氮肥(硝酸钾、尿素、硫酸铵)对烟草富集镉的影响,以及根际细菌群落结构的变化。【结果】施用3种氮肥均在一定程度上改善了烟草的生长,并提高了植株镉含量及镉提取量。其中施用尿素效果最佳,使烟草叶片中镉含量从15.07 mg·kg^(-1)提升到22.70~23.00 mg·kg^(-1),提高了50.6%~52.6%,并使烟草植株镉提取量从23.13μg·pot^(-1)提高到37.41~37.43μg·pot^(-1),较对照显著提高了63.4%~63.6%。另外,施用尿素降低了根际有效镉含量,这可能与烟草对镉的大量吸收有关。通过16S rRNA高通量测序技术发现,施用尿素显著提高了根际细菌群落的多样性和丰富度,并改变了细菌属水平的群落结构。其中,施用尿素使鞘氨醇单胞菌丰度显著提高,这可能是尿素提高烟草镉积累的另一重要原因。【结论】试验结果能为以合理施肥为手段提高烟草对镉污染土壤的修复效率奠定理论基础。

【Objective】Tobacco is expected to be an ideal phytoremediation plant for cadmium conta-minated soil,but the affects of nitrogen fertilizer on cadmium accumulation in tobacco and their mechanisms need to be clear and definite.【Method】The effects of three nitrogen fertilizers(potassium nitrate,urea and ammonium sulfate)on cadmium accumulation in tobacco and the changes of bacterial community stru-cture in rhizosphere were analyzed by laboratory experiments.【Result】The results showed that the application of three nitrogen fertilizer improved the growth of tobacco to a certain extent,and increased the cadmium content in tobacco and cadmium extraction.Among them,urea application was most effective,which increased the cadmium content in tobacco leaves from 15.07 mg·kg^(-1)to 22.70-23.00 mg·kg^(-1)by 50.6%-52.6%,and increased the cadmium extraction by tobacco plants from 23.13μg·pot^(-1)to 37.41-37.43μg·pot^(-1),by 63.4%-63.6%compared with the control.In addition,the application of urea reduced the available Cd content in rhizosphere,which may be related to the large uptake of Cd by tobacco.The 16S rRNA high-throughput sequencing indicated that urea application significantly increased the diversity and richness of rhizosphere bacterial community,and changed the community structure of bacterial genus level.Among them,the abundance of Sphingomonas sp.was significantly increased by urea application,which may be another important reason for urea to enhance cadmium accumulation in tobacco.【Conclusion】These experiment results could laid a theoretical foundation for improving the remediation efficiency of tobacco to cadmium contamination soil by rational fertilization.