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Elevated Atmospheric CO₂ and Nitrogen Fertilization Affect the Abundance and Community Structure of Rice Root-Associated Nitrogen-Fixing Bacteria.

ABSTRACT: Elevated atmospheric CO₂ (eCO₂) results in plant growth and N limitation, yet how root-associated nitrogen-fixing bacterial communities respond to increasing atmospheric CO₂ and nitrogen fertilization (eN) during the growth stages of rice is unclear. Using the nifH gene as a molecular marker, we studied the combined effect of eCO₂ and eN on the diazotrophic community and abundance at two growth stages in rice (tillering, TI and heading, HI). Quantitative polymerase chain reaction (qPCR) showed that eN had no obvious effect on nifH abundance in rice roots under either ambient CO₂ (aCO₂) or eCO₂ treatment at the TI stage; in contrast, at the HI, nifH copy numbers were increased under eCO₂ and decreased under aCO₂. For rhizosphere soils, eN significantly reduced the abundance of nifH under both aCO₂ and eCO₂ treatment at the HI stage. Elevated CO₂ significantly increased the nifH abundance in rice roots and rhizosphere soils with nitrogen fertilization, but had no obvious effect without N addition at the HI stage. There was a significant interaction [CO₂ × N fertilization] effect on nifH abundance in root zone at the HI stage. In addition, the nifH copy numbers in rice roots were significantly higher at the HI stage than at the TI stage. Sequencing analysis indicated that the root-associated diazotrophic community structure tended to cluster according to the nitrogen fertilization treatment and that Rhizobiales were the dominant diazotrophs in all root samples at the HI stage. Additionally, nitrogen fertilization significantly increased the relative abundance of Methylosinus (Methylocystaceae) under eCO₂ treatment, but significantly decreased the relative abundance of Rhizobium (Rhizobiaceae) under aCO₂ treatment. Overall, the combined effect of eN and eCO₂ stimulates root-associated diazotrophic methane-oxidizing bacteria while inhibits heterotrophic diazotrophs.

SUBMITTER: Liu J

PROVIDER: S-EPMC8103900 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundThe nitrogen (N) and protein concentrations in plant tissues exposed to elevated CO2 (eCO2) generally decline , such declines in forage grass composition are expected to have negative implications for the nutritional and economic value of grass. Plants require N for the production of a photosynthetically active canopy and storage proteins in the tissues, whose functionality will strongly influence productivity and quality. The objective of this study was to investigate whether eCO2 plus N-fertilization increases growth and N nutrition of Agropyron mongolicum, and the dependence of this improvement on the coordination between root and leaf development.MethodsWe analyzed A. mongolicum from field-grown within the open-top chambers (OTCs) facility under two atmospheric CO2 (ambient, 400 ± 20 µmol mol-1, aCO2, and elevated, 800 ± 20 µmol mol-1, eCO2) and three N-fertigation treatments (control, low N-fertigation , and high N-fertigation) for two months.ResultsElevated CO2 plus N-fertigation strongly increased shoot and root biomass, and the nitrogen and protein concentrations of A. mongolicum compared to those plants at aCO2 levels. Increased N content in leaves and reduced specific leaf area (SLA) at a high N supply could alleviate photosynthetic acclimation to eCO2 and drive the production of greater shoot biomass with the potential for higher photosynthesis, productivity, and nutritional quality. The increased root length (RL), the ratio of total aboveground N taken up per RL (TN/RL), stomatal conductance (Gs), and transpiration rate (Tr) contribute to the transpiration-driven mass flow of N, consequently increasing N uptake by roots. In addition, a smaller percentage of N remained as unassimilated nitrate ( NO3- ) under eCO2, indicating that assimilation of NO3- into proteins was not inhibited by eCO2. These findings imply that grass productivity and quality will enhance under anticipated elevated CO2 concentration when effective management measures of N-fertilization are employed.

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Elevated Atmospheric CO₂ and Nitrogen Fertilization Affect the Abundance and Community Structure of Rice Root-Associated Nitrogen-Fixing Bacteria.

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Elevated Atmospheric CO2 and Nitrogen Fertilization Affect the Abundance and Community Structure of Rice Root-Associated Nitrogen-Fixing Bacteria.

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OmicsDI is part of the ELIXIR infrastructure

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Elevated Atmospheric CO₂ and Nitrogen Fertilization Affect the Abundance and Community Structure of Rice Root-Associated Nitrogen-Fixing Bacteria.