School of Earth & Sustainability, University of Massachusetts, Amherst, Massachusetts 01003, United States.
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
Environ Sci Technol. 2024 Oct 22;58(42):18713-18722. doi: 10.1021/acs.est.4c04108. Epub 2024 Oct 10.
Plant roots and associated microbes release a diverse range of functionally distinct exudates into the surrounding rhizosphere with direct impacts on soil carbon storage, nutrient availability, and contaminant dynamics. Yet mechanistic linkages between root exudation and emergent biogeochemical processes remain challenging to measure nondestructively, in real soil, over time. Here we used a novel combination of microsensors with high-resolution mass spectrometry to measure, nondestructively, changing exudation and associated biogeochemical dynamics along single growing plant roots (). We found that metabolite and dissolved organic carbon (DOC) concentrations as well as microbial growth, redox potential (), and pH dynamics vary significantly among bulk soil, root tip, and more mature root zones. Surprisingly, the significant spike of rhizosphere DOC upon root tip emergence did not significantly correlate with any biogeochemical parameters. However, the presence of sugars significantly correlated with declines in following the arrival of the root tip, likely due to enhanced microbial oxygen demand. Similarly, the presence of organic acids significantly correlated to declines in pH upon root tip emergence. Overall, our measurements highlight how different exudates released along growing roots create functionally distinct soil microenvironments that evolve over time.
植物根系及其相关微生物会向周围的根际环境中释放出多种多样、功能各异的分泌物，这些分泌物直接影响土壤碳储存、养分可用性和污染物动态。然而，根系分泌物与新兴生物地球化学过程之间的机制联系仍然难以在真实土壤中进行非破坏性、随时间推移的测量。在这里，我们使用了一种新颖的微传感器与高分辨率质谱相结合的方法，对单株生长植物根系（）上不断变化的分泌物及其相关生物地球化学动态进行非破坏性、实时测量。我们发现，代谢物和溶解有机碳（DOC）浓度以及微生物生长、氧化还原电位（Eh）和 pH 动态在整个土壤、根尖和更成熟的根区之间存在显著差异。令人惊讶的是，根尖出现时根际 DOC 的显著峰值与任何生物地球化学参数都没有显著相关性。然而，糖的存在与根尖到达后Eh 的下降显著相关，这可能是由于微生物对氧气的需求增加所致。同样，有机酸的存在与根尖出现时 pH 的下降显著相关。总的来说，我们的测量结果强调了沿着生长的根系释放的不同分泌物如何在时间的推移下创造出功能上不同的土壤微环境。
