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

Jones, Davey L.; Nguyen, Christophe; Finlay, Roger D.

doi:10.1007/s11104-009-9925-0

Cited by 1,345 publications

(865 citation statements)

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“…A notable feature of the rhizosphere is the deposition of organic carbon via exudates and/or decomposition of dead tissue, which may account for up to 40 % of the total input of C to the soil and is considered the major driver of microbial processes (Jones et al, 2009). This deposition of organic carbon is in agreement with the higher OM contents observed in the rhizospheric soils in relation to the nonrhizospheric soils (Table 2).…”

Section: Discussionmentioning

confidence: 99%

Soil nitrogen dynamics after Brachiaria desiccation

Castoldi

Reis

Pivetta

et al. 2013

Rev. Bras. Ciênc. Solo

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SUMMARYBrachiaria species, particularly B. humidicola, can synthesize and release compounds from their roots that inhibit nitrification, which can lead to changes in soil nitrogen (N) dynamics, mainly in N-poor soils. This may be important in croplivestock integration systems, where brachiarias are grown together with or in rotation with grain crops. The objective of the present study was to determine whether this holds true in N-rich environments and if other Brachiaria species have the same effect. The soil N dynamics were evaluated after the desiccation of the species B. brizantha, B. decumbens, B. humidicola, and B. ruziziensis, which are widely cultivated in Brazil. The plants were grown in pots with a dystroferric Red Latosol in a greenhouse. Sixty days after sowing, the plants were desiccated using glyphosate herbicide. The plants and soil were analyzed on the day of desiccation and 7, 14, 21 and 28 days after desiccation. The rhizosphere soil of the grasses contained higher levels of organic matter, total N and ammonium than the non-rhizosphere soil. The pH was lowest in the rhizosphere of B. humidicola, which may indicate that this species inhibits the nitrification process. However, variations in the soil ammonium and nitrate levels were not sufficient to confirm the suppressive effect of B. humidicola. The same was observed for B. brizantha, B. decumbens and B. ruziziensis, thereby demonstrating that, where N is abundant, none of the brachiarias studied has a significant effect on the nitrification process in soil.Index terms: Brachiaria brizantha, Brachiaria decumbens, Brachiaria humidicola, Brachiaria ruziziensis, nitrification, rhizosphere.( RESUMO: DINÂMICA DO NITROGÊNIO NO SOLO APÓS A DESSECAÇÃO DE BRACHIARIASEspécies do gênero Brachiaria, particularmente a B. humidicola, podem sintetizar e liberar de suas raízes compostos que inibem o processo de nitrificação, o que pode provocar alterações na dinâmica do nitrogênio (N) no solo, principalmente em solos com baixa disponibilidade de N. Isso pode ser importante em sistemas com integração lavoura-pecuária, em que a forrageira é cultivada junto ou em rotação com culturas graníferas. Neste estudo, objetivou-se determinar se isso ocorre também em ambiente mais rico em N e se outras espécies de Brachiaria têm o mesmo efeito. Para tal, avaliou-se a dinâmica do N no solo após a dessecação de B. brizantha, B. decumbens, B. humidicola e B. ruziziensis, espécies amplamente cultivadas no Brasil. As plantas foram cultivadas em vasos com um Latossolo Vermelho distroférrico, em casa de vegetação. Sessenta dias após a semeadura, as plantas foram dessecadas com aplicação do herbicida glifosato. Foram realizadas análises de planta e solo, na data da dessecação e aos 7, 14, 21 e 28 dias após a dessecação. Os maiores teores de matéria orgânica, N-total e amônio foram encontrados no solo rizosférico das plantas. A rizosfera da B. humidicola apresentou ainda o menor valor de pH, o que poderia estar associado ao efeito supressivo dessa espécie no processo de nitrificaç...

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Section: Discussionmentioning

confidence: 99%

Soil nitrogen dynamics after Brachiaria desiccation

Castoldi

Reis

Pivetta

et al. 2013

Rev. Bras. Ciênc. Solo

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“…From 10 to 20% of photosynthetic C fixed by plants is released into the rhizosphere as rhizodeposits: that is, soluble exudates, insoluble secretions, rhizosphere C flow and detrital root material (Gregory, 2006;Wichern et al, 2008;Jones et al, 2009). Some of this rhizodeposition is used by microbial communities for respiration and biomass production, and subsequent turnover of the biomass contributes to soil organic matter (SOM) pools.…”

Section: Introductionmentioning

confidence: 99%

Effects of soil type and composition of rhizodeposits on rhizosphere priming phenomena

Lloyd

Ritz

Paterson

et al. 2016

Soil Biology and Biochemistry

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Inputs of fresh plant-derived C may stimulate microbially-mediated turnover of soil organic matter (SOM) in the rhizosphere. But studies of such 'priming' effects in artificial systems often produce conflicting results, depending on such variables as rates of substrate addition, substrate composition, whether pure compounds or mixtures of substrates are used, and whether the addition is pulsed or continuous. Studies in planted systems are less common, but also produce apparently conflicting results, and the mechanisms of these effects are poorly understood.To add to the evidence on these matters, we grew a C4 grass for 61 d in two contrasting soilsan acid sandy soil and a more fertile clay-loam -which had previously only supported C3 vegetation. We measured total soil respiration and its C isotope composition, and used the latter to partition the respiration between plant-and soil-C sources. We found SOM turnover was enhanced (i.e. positive priming) by plant growth in both soils. In treatments in which the grass was clipped, net growth was greatly diminished, and priming effects were correspondingly weak. In treatments without clipping, net plant growth, total soil respiration and SOM-derived respiration were all much greater. Further, SOM-derived respiration increased over time in parallel with increases in plant growth, but the increase was delayed in the less fertile soil. We conclude the observed priming effects were driven by microbial demand for N, fuelled by deposition of C substrate from roots and competition with roots for N. The extent of priming depended on soil type and plant growing conditions.In a further experiment, we simulated rhizodeposition of soluble microbial substrates in the same two soils with near-continuous additions for 19 d of either C4-labelled sucrose (i.e. a simple single substrate) or a maize root extract (i.e. a relatively diverse substrate), and we measured soil respiration and its C isotope signature. In the more fertile soil, sucrose induced increasingly positive priming effects over time, whereas the maize root extract produced declining priming effects over time. We suggest this was because N and other nutrients were provided from the mineralization of this more diverse substrate. In the less-fertile soil, microbial N demand was probably never satisfied by the combined mineralization from added substrate and soil organic matter. Therefore priming

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“…Such changes are attributed to the rich carbon energy sources provided by the plant. Indeed, plants release, on average, 10 to 15% (Jones et al 2009) of their photosynthetic assimilates into the rhizosphere, a process called rhizodeposition (Dennis et al 2010). These rhizodeposits originate from sloughed off root border and root border-like cells from root tips, active root exudation, and cell lysis.…”

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confidence: 99%

Spatio Temporal Influence of Isoflavonoids on Bacterial Diversity in the Soybean Rhizosphere

White¹,

Jothibasu²,

Reese³

et al. 2015

MPMI

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High bacterial density and diversity near plant roots has been attributed to rhizodeposit compounds that serve as both energy sources and signal molecules. However, it is unclear if and how specific rhizodeposit compounds influence bacterial diversity. We silenced the biosynthesis of isoflavonoids, a major component of soybean rhizodeposits, using RNA interference in hairy-root composite plants, and examined changes in rhizosphere bacteriome diversity. We used successive sonication to isolate soil fractions from different rhizosphere zones at two different time points and analyzed denaturing gradient gel electrophoresis profiles of 16S ribosomal RNA gene amplicons. Extensive diversity analysis of the resulting spatio temporal profiles of soybean bacterial communities indicated that, indeed, isoflavonoids significantly influenced soybean rhizosphere bacterial diversity. Our results also suggested a temporal gradient effect of rhizodeposit isoflavonoids on the rhizosphere. However, the hairy-root transformation process itself significantly altered rhizosphere bacterial diversity, necessitating appropriate additional controls. Gene silencing in hairy-root composite plants combined with successive sonication is a useful tool to determine the spatio temporal effect of specific rhizodeposit compounds on rhizosphere microbial communities.Pioneering microbiology studies by L. Hiltner in the early 1900s showed that the highest microbial density in soils occurs very close to plant roots (Hinsinger and Marschner 2006). For example, a four-to fivefold increase in CFU was observed in root-surface scrapings as compared with soil samples 0.5 cm away from the roots (Clark 1940). Such changes are attributed to the rich carbon energy sources provided by the plant. Indeed, plants release, on average, 10 to 15% (Jones et al. 2009) of their photosynthetic assimilates into the rhizosphere, a process called rhizodeposition (Dennis et al. 2010). These rhizodeposits originate from sloughed off root border and root border-like cells from root tips, active root exudation, and cell lysis. Rhizodeposits are composed of sugars, amino acids, organic acids, fatty acids, proteins, ions, secondary metabolites, mucilage, water, and miscellaneous carbon-containing compounds (Bais et al. 2006;Dennis et al. 2010).Significant evidence accumulated over the years indicates that the composition of root microbial communities is influenced, in large part, by the plant species and its developmental stage (Micallef et al. 2009;Mougel et al. 2006;Weisskopf et al. 2006). Indeed, an intricate coevolution of plants and rhizosphere microbial communities was suggested by the observation that resident plants or their root exudates are capable of maintaining the biomass and diversity of soil fungal communities to a much greater extent than nonresident or introduced plants ). This is supported by the observation that invasive weeds have the ability to significantly influence native rhizosphere microbial communities to exert their dominance in new environments (Inder...

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

Cited by 1,345 publications

References 249 publications

Soil nitrogen dynamics after Brachiaria desiccation

Soil nitrogen dynamics after Brachiaria desiccation

Effects of soil type and composition of rhizodeposits on rhizosphere priming phenomena

Spatio Temporal Influence of Isoflavonoids on Bacterial Diversity in the Soybean Rhizosphere

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