Carbon flow in the rhizosphere: carbon trading at the soil–root interface

By Davey L. Jones, C. Nguyen, R. Finlay. Plant and Soil, 2009

1,572 citations recorded by the source corpus.

The loss of organic and inorganic carbon from roots into soil underpins nearly all the major changes that occur in the rhizosphere. In this review we explore the mechanistic basis of organic carbon and nitrogen flow in the rhizosphere. It is clear that C and N flow in the rhizosphere is extremely complex, being highly plant and environment dependent and varying both spatially and temporally along the root. Consequently, the amount and type of rhizodeposits (e.g. exudates, border cells, mucilage) remains highly context specific. This has severely limited our capacity to quantify and model the amount of rhizodeposition in ecosystem processes such as C sequestration and nutrient acquisition. It is now evident that C and N flow at the soil–root interface is bidirectional with C and N being lost from roots and taken up from the soil simultaneously. Here we present four alternative hypotheses to explain why high and low molecular weight organic compounds are actively cycled in the rhizosphere. These include: (1) indirect, fortuitous root exudate recapture as part of the root’s C and N distribution network, (2) direct re-uptake to enhance the plant’s C efficiency and to reduce rhizosphere microbial growth and pathogen attack, (3) direct uptake to recapture organic nutrients released from soil organic matter, and (4) for inter-root and root–microbial signal exchange. Due to severe flaws in the interpretation of commonly used isotopic labelling techniques, there is still great uncertainty surrounding the importance of these individual fluxes in the rhizosphere. Due to the importance of rhizodeposition in regulating ecosystem functioning, it is critical that future research focuses on resolving the quantitative importance of the different C and N fluxes operating in the rhizosphere and the ways in which these vary spatially and temporally.

Subfields: Plant Science, Soil Science

View Paper: https://www.semanticscholar.org/paper/541bde1f7410091df5a38ff09cbb04b88485a57f

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Citations in the corpus

Structure and Function of the Bacterial Root Microbiota in Wild and Domesticated Barley (2015, background): “This process, known as rhizodeposition, has been proposed as the major mechanism that enables plants to sustain their microbiota (Jones et al., 2009).”
Stimulation of Plant Growth through Interactions of Bacteria and Protozoa: Testing the Auxiliary Microbial Loop Hypothesis (2012, background): “This zone has been suggested to be characterized by fierce microbial competition between bacteria and plant roots for available nutrients (Hodge et al. 2000, Jones et al. 2009).”
Acquisition of phosphorus and other poorly mobile nutrients by roots. Where do plant nutrition models fail? (2011, background): “Rhizodeposition, which is comprising the release of a broad range of plant-derived compounds, beyond root exudates, is a key biogeochemical process occurring in the rhizosphere (Dennis et al. 2010; Hinsinger et al. 2005, 2009; Jones et al. 2009).”
Soil microbial organic nitrogen uptake is regulated by carbon availability (2014, background): “There are two important concepts here: firstly, labile nutrients are a patchy resource in the soil, with large concentration gradients over the mm emm scale (Jones et al., 2009b).”
Are root exudates more important than other sources of rhizodeposits in structuring rhizosphere bacterial communities? (2010, background): “Assuming that roots and microorganisms contribute equally to respiration in the rhizosphere (Kuzyakov et al., 2001; Kuzyakov, 2006) rhizodeposition represents approximately 11% of net fixed carbon and 27% of carbon allocated to roots (Jones et al., 2009).”
Arbuscular Mycorrhiza — a Key Component of Sustainable Plant-Soil Ecosystems (2012, background): “The beneficial activities of the rhizosphere microbiota include the increased availability of plant nutrients, improvement of nutrient uptake and protection against root pathogens (Kloepper 1992; Linderman 1992; Glick 1995; Barea et al. 1997, 2002b, 2005b; Faure et al. 2009; Hartmann et al. 2009; Jo”
Distribution of phosphatase activity and various bacterial phyla in the rhizosphere of Hordeum vulgare L. depending on P availability (2015, background): “Bacteria that started growing at the root tip, where exudation is highest (Jones et al., 2009), likely could not attach quick enough to the root tip, and were passed by the fast moving root tip.”