Background and aims

Selenium (Se) deficiency in soil and human diets may worsen with elevated atmospheric carbon dioxide (eCO₂). However, current research focused on essential nutrient elements, such as nitrogen, phosphorus and potassium, the effects of eCO₂ on Se accumulation in staple crops are understudied. Here, the Se-hyperaccumulator Cardamine hupingshanensis was selected to investigate the impacts on Se accumulation, and associated rhizobacterial communities under eCO₂ (800 ppm).

Methods

Simulated CO₂-elevated greenhouse experiments were conducted, and Se concentrations were measured using inductively coupled plasma mass spectrometry (ICP-MS). Bacterial communities in bulk, rhizosphere and rhizoplane soils were analyzed via high-throughput 16 S rRNA amplicon sequencing.

Results

The eCO₂ increased Se levels by three- to four-fold in C. hupingshanensis cultivated in natural soils. Rhizobacterial communities exhibited notable shifts under eCO₂ with increased relative abundances of Bacillaceae, Rhizobiaceae, Flavobacteriaceae and Xanthomonadaceae, but decreased Sphingomonadaceae, Gemmatimonadaceae and Micrococcaceae. Genera such as Nannocystis, Steroidobacter, Dactylosporangium and Brevundimonas, demonstrated significant positive correlation (P < 0.05) with total Se, bioavailable Se and pH in soils. The abundances of the bacteria involved in Se metabolism exhibited significant positive correlations (P < 0.05) with total inorganic carbon (TIC), total organic carbon (TOC) and carbon metabolism. Structural Equation Modelling analysis indicated that eCO₂ significantly increased soil bioavailable Se and C. hupingshanensis Se levels.

Conclusion

The eCO₂ promoted Se accumulation in C. hupingshanensis roots by regulating soil pH, TIC and bioavailable Se levels, while reshaping rhizobacterial communities. This study contributes to understanding associated mechanisms of Se accumulation under eCO₂, particularly in plant-rhizobacterial interactions.

中文翻译：

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CO2 浓度升高对小豆蔻硒积累及相关根际细菌群落的影响

 背景和目标

土壤和人类饮食中的硒 （Se） 缺乏症可能会随着大气中二氧化碳 （eCO₂） 的增加而恶化。然而，目前的研究集中在必需营养元素，如氮、磷和钾，eCO₂ 对主食作物中硒积累的影响研究不足。在这里，选择了 Se 超积累剂 Cardamine hupingshanensis 来研究 eCO₂ （800 ppm） 下对 Se 积累和相关根际细菌群落的影响。

 方法

进行了模拟 CO₂ 升高的温室实验，并使用电感耦合等离子体质谱 （ICP-MS） 测量 Se 浓度。通过高通量 16 S rRNA 扩增子测序分析块状、根际和根际土壤中的细菌群落。

 结果

eCO₂ 使天然土壤中栽培的湖山栗的硒水平提高了 3 到 4 倍。根际细菌群落在 eCO₂ 下表现出显着变化，芽孢杆菌科、根际菌科、黄杆菌科和黄杆菌科的相对丰度增加，但鞘氨醇单胞菌科、葡萄藻科和微球菌科的相对丰度增加。微孢子菌属（Nannocystis）、类固体杆菌属（Steroidobacter）、指孢子囊属（Dactylosporangium）和短孢子菌属（Brevundimonas）与土壤中的总硒、生物可利用硒和pH值呈显著正相关（P < 0.05）。参与硒代谢的细菌丰度与总无机碳 （TIC） 、总有机碳 （TOC） 和碳代谢呈显著正相关 （P < 0.05）。结构方程模型分析表明，eCO₂ 显著提高了土壤生物有效性 Se 和 C. hupingshanensis Se 水平。

 结论

eCO₂ 通过调节土壤 pH 值、TIC 和生物可利用的硒水平促进湖平山栗根系中硒的积累，同时重塑根际细菌群落。本研究有助于了解 eCO₂ 下 Se 积累的相关机制，特别是在植物-根际细菌相互作用中。