Abstract Biochar application and rising carbon dioxide (CO2) concentrations are likely to influence both aboveground and belowground plant processes. However, little is known about the influence of biochar and CO2 enrichment on root exudation, as well as their interactive effects. The aim of this study was to reveal whether rice paddy root exudates responded to biochar and CO2 enrichment and whether this effect varied at different plant growth stages. Rice was grown in growth chambers with different biochar addition rates (1%, 2%, 3%, 4%, and 5% by weight) under both ambient (aCO2, 400 ppm) and elevated (eCO2, 700 ppm) CO2 levels. Root exudation variables were measured at the tillering and stem elongation stages. Electrical conductivity (EC), amino acid (AA), indole acetic acid (IAA), and abscisic acid (ABA) levels were significantly increased but cytokinin (CYT) concentrations decreased in response to biochar addition rates. In addition, eCO2 increased root and shoot biomass but decreased the root-to-shoot ratio. eCO2 significantly decreased EC, potassium (K+), ABA, and CYT concentrations, while the opposite pattern was found for AA and IAA. Significant interactive effects between biochar addition and eCO2 were only found on CYT and AA concentrations, while no significant interactive effects of plant growth stage, biochar addition, and eCO2 were found on root exudation. These results indicate that the additive effects of biochar and eCO2 should be integrated into assessments of carbon storage ability in the future. Understanding the different responses of these variables within the rhizosphere is crucial for predicting changes in the carbon balance in response to biochar application and climate change.

中文翻译：

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CO2升高时根系分泌物对生物炭施用的不同反应

摘要 生物炭应用和二氧化碳 (CO2) 浓度升高可能会影响地上和地下植物过程。然而，关于生物炭和 CO2 富集对根系分泌物的影响以及它们的交互作用知之甚少。本研究的目的是揭示稻田根系分泌物是否对生物炭和二氧化碳富集有反应，以及这种影响在不同植物生长阶段是否有所不同。在环境 (aCO2, 400 ppm) 和升高 (eCO2, 700 ppm) CO2 水平下，水稻在具有不同生物炭添加率（按重量计 1%、2%、3%、4% 和 5%）的生长室中生长。在分蘖和茎伸长阶段测量根系分泌物变量。电导率（EC）、氨基酸（AA）、吲哚乙酸（IAA）、和脱落酸 (ABA) 水平显着增加，但细胞分裂素 (CYT) 浓度随着生物炭添加速率而降低。此外，eCO2 增加了根和地上部的生物量，但降低了根与地上部的比率。eCO2 显着降低了 EC、钾 (K+)、ABA 和 CYT 的浓度，而 AA 和 IAA 的模式则相反。生物炭添加和eCO2 之间的显着交互作用仅在CYT 和AA 浓度上被发现，而植物生长阶段、生物炭添加和eCO2 对根系分泌物没有显着的交互作用。这些结果表明，未来应将生物炭和 eCO2 的相加效应纳入碳储存能力的评估中。