Sampling root exudates - Mission impossible?
Sampling root exudates - Mission impossible?
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DOI：
10.1016/j.rhisph.2018.06.004
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发表时间：
2018-06-01
期刊：
影响因子：
3.7
通讯作者：
Jones, David L.
中科院分区：
文献类型：
--
作者：
Oburger, Eva;Jones, David L.
植物根系代谢产物释放的数量、质量和时空动态的准确信息对于理解根系分泌物在发生在根-微生物-土壤-界面的生物地球化学过程中的功能意义至关重要。当今分析技术的重大进步使我们能够更好地了解根分泌物中存在的丰富多样性的化合物，但最终分泌物采样策略的选择将决定所获得的分泌物结果的生态意义。不幸的是，在过去，很少有人考虑到用来采样根系分泌物的实验策略。到目前为止，我们对根分泌物的了解主要是基于在营养液培养(水培)中生长和取样的植物。尽管水培系统具有运行效益，但问题仍然是，如何将在这些人工条件下获得的具有生态相关性的渗出结果与土壤环境进行比较，特别是在渗出物驱动的根际过程的背景下。然而，土壤中根系分泌物的定量和定性测量充满了问题，这是因为：(I)微生物群落不断地从溶液中去除分泌物；(Ii)由于分泌物被吸附到固相而从溶液中损失；以及(Iii)从土壤有机质分解中同时释放化合物。虽然目前还没有一种完美的根分泌物采样方法，但如果适当地应用和解释，基于土壤的方法仍然可以为自然土壤环境中的分泌物动态提供更现实的见解。该综述旨在提供不同的根分泌物取样方法及其优点和局限性的概述，以支持为任何特定的研究问题选择最合适的实验程序。我们阐述了在选择实验方法时需要考虑的关键方法方面，如生长和采样介质(土壤、水培)、无菌、采样位置(整个根系、单个根段)以及植物年龄、白天、影响采样事件持续时间和时间的代谢物的重新吸收以及数据呈现。此外，我们还总结了分析根系分泌物的主要分析方法，从液体样品分析到同位素示踪和成像技术。
Accurate information about the quantity, quality and spatiotemporal dynamics of metabolite release from plant roots is vital to understanding the functional significance of root exudates in biogeochemical processes occurring at the root-microbe-soil-interface. Significant progress in analytical techniques nowadays allows us to gain a much better picture of the rich diversity of compounds that are present in root exudates, but ultimately the choice of exudation sampling strategy will determine the ecological significance of obtained exudation results. Unfortunately, in the past, little consideration has been given to the experimental strategy used to sample root exudates. To date, our knowledge on root exudation is mainly based on plants grown and sampled in nutrient solution culture (hydroponics). Despite the operational benefit of hydroponic systems, the question remains as to how ecologically relevant exudation results obtained under these artificial conditions are compared to soil environments, particularly in the context of exudate driven rhizosphere processes. The quantitative and qualitative measurement of root exudation in soil, however, is fraught with problems due to: (i) continual removal of exudates from solution by the microbial community; (ii) loss of exudates from solution due to their sorption to the solid phase; and (iii) simultaneous release of compounds from soil organic matter breakdown. While a perfect method for sampling root exudates does not exist, soil based approaches, if appropriately applied and interpreted, may still provide more realistic insights into exudation dynamics in natural soil environments. This review aims to provide an overview of different root exudation sampling approaches and their advantages and limitations to support the selection of the most suitable experimental procedure for any specific research question. We address critical methodological aspects that need to be considered in the choice of experimental approach, like growth and sampling medium (soil, hydroponic), sterility, sampling location (whole root system, individual root segments) as well as plant age, daytime, re-uptake of metabolites affecting duration and timing of the sampling event and data presentation. In addition, we summarize the main analytical approaches to analyze root exudates, ranging from liquid sample analysis to isotope tracking and imaging techniques.