Sampling root exudates – Mission impossible?

Oburger, Eva; Jones, Davey L.

doi:10.1016/j.rhisph.2018.06.004

Cited by 285 publications

(269 citation statements)

References 234 publications

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“…To aid in more definitive identification of exuded metabolites, modern practices employ a mixture of sampling techniques (hydroponic and aeroponic exudate collection methods), coupled with highresolution mass profiling (such as LC-MS combined with standard libraries and MS e fragmentation spectra) for rigorous assessment of plant exudate metabolomics (Kuijken et al, 2014;van Dam & Bouwmeester, 2016;Oburger & Jones, 2018). Although hydroponic collection methods are direct, they are limited by the artificial growth environment, affecting root physiology and morphology (Oburger & Jones, 2018). Alternatively, samples taken from natural soils can be marred by high chemical complexity (this noise originates from the soil, the plant and/or microbially associated metabolites), confounding identification of the origin of derived metabolites.…”

Section: Box 1 a Case For Using Mixed Methodologies In Root Exudate Cmentioning

confidence: 99%

Plant root exudation under drought: implications for ecosystem functioning

2019

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Summary Root exudates are a pathway for plant–microbial communication and play a key role in ecosystem response to environmental change. Here, we collate recent evidence that shows that plants of different growth strategies differ in their root exudation, that root exudates can select for beneficial soil microbial communities, and that drought affects the quantity and quality of root exudation. We use this evidence to argue for a central involvement of root exudates in plant and microbial response to drought and propose a framework for understanding how root exudates influence ecosystem form and function during and after drought. Specifically, we propose that fast‐growing plants modify their root exudates to recruit beneficial microbes that facilitate their regrowth after drought, with cascading impacts on their abundance and ecosystem functioning. We identify outstanding questions and methodological challenges that need to be addressed to advance and solidify our comprehension of the importance of root exudates in ecosystem response to drought.

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Section: Box 1 a Case For Using Mixed Methodologies In Root Exudate Cmentioning

confidence: 99%

Plant root exudation under drought: implications for ecosystem functioning

2019

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“…Despite early studies highlighting the role of faunal–microbial interactions in the rhizosphere for the mineralization and plant uptake of soil N (Clarholm, ; Ingham, Trofymow, Ingham, & Coleman, ; Ritz & Griffiths, ), major uncertainties exist about the influence of plant exudates on nutrient release via these trophic interactions (Blagodatskaya et al, ; Cole, Staddon, Sleep, & Bardgett, ). Our poor ability to measure the spectrum and amounts of root exudates in soil in a quantitatively rigorous manner (Oburger & Jones, ) calls for further research to overcome this bottleneck. In the case of priming, it is highly likely that both negative and positive priming will occur in different regions of the root system (due to spatial patterns of root exudation, microbial activity and soil organic C and N heterogeneity).…”

Section: Priming Soil Organic Matter Decomposition By Micro‐organismsmentioning

confidence: 99%

A plant perspective on nitrogen cycling in the rhizosphere

et al. 2019

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Nitrogen is the major nutrient limiting plant growth in terrestrial ecosystems, and the transformation of inert nitrogen to forms that can be assimilated by plants is mediated by soil micro‐organisms. The last decade has witnessed many significant advances in our understanding of plant–microbe interactions with evidence that plants have evolved multiple strategies to cope with nitrogen limitation by shaping and recruiting nitrogen‐cycling microbial communities. However, most studies have typically focused on the impact of plants on only one, or relatively few, processes within the nitrogen cycle. This review synthesizes recent advances in our understanding of the various routes by which plants influence the availability of nitrogen via an array of interactions with different guilds of nitrogen‐cycling micro‐organisms. We also propose a plant trait‐based framework for linking plant nitrogen acquisition strategies to the activities of nitrogen‐cycling microbial guilds. In doing so, we provide a more comprehensive picture of the ecological relationships between plants and nitrogen‐cycling micro‐organisms in terrestrial ecosystems. Finally, we identify previously overlooked processes within the nitrogen cycle that could be targeted in future research and be of interest for plant health or for improving plant nitrogen acquisition, while minimizing nitrogen inputs and losses in sustainable agricultural systems. A plain language summary is available for this article.

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“…This set-up allows for disentangling the implications of differences in the quantity and quality of root exudates, as well as differences in soil properties and microbial communities, for respiration, which is not possible using 13 CO 2 pulse labelling. However, root exudates collected and readded in aqueous solution to isolated soil samples might well behave differently than in an undisturbed rhizosphere (Oburger et al, 2013;Oburger & Jones, 2018). Ideally, our method would be combined with 13 CO 2 pulse labelling and flux measurements in an intact system, as well as detailed analysis of 13 C-enriched root exudate metabolites and microbial communities.…”

Section: Researchmentioning

confidence: 99%

Changes in root‐exudate‐induced respiration reveal a novel mechanism through which drought affects ecosystem carbon cycling

et al. 2019

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Summary Root exudates play an important role in ecosystem response to climate change, but the functional consequences of drought‐induced changes in the quality of root exudates are unknown. Here, we addressed this knowledge gap in a unique experimental approach. We subjected two common grassland species that differ widely in their growth strategies and root systems, the grass Holcus lanatus and the forb Rumex acetosa, to 2 wk of drought. We collected root exudates and soils at the end of the drought and after 2 wk of recovery and readded all root exudates to all soils in a fully reciprocal set‐up to measure root‐exudate‐induced respiration. We found that soil treatment was unimportant for determining root‐exudate‐induced respiration. By contrast, root exudates collected from plants that had experienced drought clearly triggered more soil respiration than exudates from undroughted plants. Importantly, this increased respiration compensated for the lower rates of root exudation in droughted plants. Our findings reveal a novel mechanism through which drought can continue to affect ecosystem carbon cycling, and a potential plant strategy to facilitate regrowth through stimulating microbial activity. These findings have important implications for understanding plant and ecosystem response to drought.

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Sampling root exudates – Mission impossible?

Cited by 285 publications

References 234 publications

Plant root exudation under drought: implications for ecosystem functioning

Plant root exudation under drought: implications for ecosystem functioning

A plant perspective on nitrogen cycling in the rhizosphere

Changes in root‐exudate‐induced respiration reveal a novel mechanism through which drought affects ecosystem carbon cycling

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