Unlocking research on rhizodeposition: a step-by-step guide for producing, sampling and analyzing

Rhizodeposits, i.e. the organic materials released by living roots into the soil, play a major role in plant interactions with their biotic and abiotic environment. However, our understanding of rhizodeposition processes has remained limited due to the methodological challenges associated with the collection and analysis of rhizodeposits. Here, we aimed to synthesize knowledge from the various fields of expertise required for studying rhizodeposition, in order to support the scientific community in making informed methodological choices and to ensure the robustness and comparability of studies. In particular, we developed an open-access decision support tool (CARROT: Collecting and Analyzing Rhizodeposits: Reviewing and Optimizing Tool), using existing literature and practical expertise from the interdisciplinary network RhizosPHARE. This tool has been designed to help newcomers and specialists in the field i) to quickly identify the most appropriate methodological option(s) in terms of plant growth conditions, sample collection and sample analysis according to their scientific question and their experimental constraints, ii) to get practical recommendation about each method, and iii) to get a direct access to additional information and references. As part of these guidelines, we also suggest a standardized protocol for collecting root exudates from hydroponically grown plants to characterize their composition. Together with the CARROT tool, this protocol paves the way towards establishing consistent, standardized methods for characterizing rhizodeposition and its impact in the plant-soil system.