Nitrogen fixation by Azospirillium brasilense in soil and the rhizosphere under controlled environmental conditions

Christiansen-Weniger, C.; Veen, Johannes A. van

doi:10.1007/bf00341483

Cited by 34 publications

(14 citation statements)

References 41 publications

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“…Under hydroponic conditions bacterial abundance at barley roots was found to increase at higher NH 4 + -N levels and could be attributed to increased rhizodeposition as measured by 14 C methods (Liljiroth et al 1990a, b). Christiansen-Weniger and Van Veen (1991) and Martins-Loução et al (2000) suggested that cracks developed by greater root branching and root initials in response to NH 4 + were responsible for higher rhizodeposition. Under natural conditions with soil as the rooting medium, the compounds released will have a profound effect on microbial population and their activities and consequently on plants.…”

Section: Discussionmentioning

confidence: 96%

RETRACTED ARTICLE: Effect of root-zone salinity and form of N on photosynthate partitioning in wheat (Triticum aestivum L.)

et al. 2008

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Carbon-14 pulse labeling technique was used to study the effect of rooting medium salinity and form and availability of N on growth and rhizodeposition of wheat (Triticum aestivum L.). Thirty days old plants grown in continuously aerated Arnon and Hoagland nutrient solution were subjected to 14 C pulse labeling for 24 h and transferred to aqueous rooting medium containing 0, 150, and 300 mM NaCl in all combinations with different forms (calcium nitrate, ammonium sulphate, and ammonium nitrate) and amounts (0.5, 1.0, 1.5, and 2.0 times the standard N concentration (150 ppm) of Arnon and Hoagland plant growth medium). Plant samples immediately after pulse labeling, following 7 days of growth under different rooting medium conditions, and the freeze-dried rooting medium were analyzed for total C and 14 C. Length and fresh/dry weight of root and shoot portions and calculated values of unaccounted 14 C were determined. Presence of NaCl in the rooting medium led to a decrease in root and shoot portions. However, NO 3 --fed plants showed better growth than NH 4 + -fed plants at all the three salinity levels. Salinity in rooting medium led to higher rhizodeposition and lower loss of 14 C. Relatively higher proportion of 14 C was released as rhizodeposits and retained in root/shoot portions of plants fed with NH 4 + or NH 4 + +NO 3 -, than those with NO 3 -, while less was respired. The specific activity of the rhizodeposits (kBq 14 C g -1 C) was also higher under saline conditions. The rhizodeposits in NH 4 + -fed plants were more highly labeled as compared to NO 3 --plants.

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Section: Discussionmentioning

confidence: 96%

RETRACTED ARTICLE: Effect of root-zone salinity and form of N on photosynthate partitioning in wheat (Triticum aestivum L.)

et al. 2008

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“…Indeed, although the nif H gene based diversity was high in the clayey soils, a lower turnover rate through time was found. An effect of ammonium on nitrogen fixation has been recognized for a long time, as nitrogenase is commonly inhibited by the presence of NH 4 + ions [82,83]. The abundant nif H-carrying bacterial groups are thought to be well-adapted to their environment [84]; however, rare diazotrophic species also responded to the same environmental parameters, indicating their functional importance.…”

Section: Discussionmentioning

confidence: 99%

Temporal Dynamics of Abundance and Composition of Nitrogen-Fixing Communities across Agricultural Soils

et al. 2013

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BackgroundDespite the fact that the fixation of nitrogen is one of the most significant nutrient processes in the terrestrial ecosystem, a thorough study of the spatial and temporal patterns in the abundance and distribution of N-fixing communities has been missing so far.Methodology/Principal FindingsIn order to understand the dynamics of diazotrophic communities and their resilience to external changes, we quantified the abundance and characterized the bacterial community structures based on the nifH gene, using real-time PCR, PCR-DGGE and 454-pyrosequencing, across four representative Dutch soils during one growing season. In general, higher nifH gene copy numbers were observed in soils with higher pH than in those with lower pH, but lower numbers were related to increased nitrate and ammonium levels. Results from nifH gene pyrosequencing confirmed the observed PCR-DGGE patterns, which indicated that the N fixers are highly dynamic across time, shifting around 60%. Forward selection on CCA analysis identified N availability as the main driver of these variations, as well as of the evenness of the communities, leading to very unequal communities. Moreover, deep sequencing of the nifH gene revealed that sandy soils (B and D) had the lowest percentage of shared OTUs across time, compared with clayey soils (G and K), indicating the presence of a community under constant change. Cosmopolitan nifH species (present throughout the season) were affiliated with Bradyrhizobium , Azospirillum and Methylocistis, whereas other species increased their abundances progressively over time, when appropriate conditions were met, as was notably the case for Paenibacilus and Burkholderia. ConclusionsOur study provides the first in-depth pyrosequencing analysis of the N-fixing community at both spatial and temporal scales, providing insights into the cosmopolitan and specific portions of the nitrogen fixing bacterial communities in soil.

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“…These studies demonstrated that N 2 -fixing bacteria are present and exhibit a N 2 -fixing activity in association with roots. However, there are discrepancies as to whether associative N 2-fixation makes a significant contribution to N supply to cereals (e.g., Chalk 1991;Christiansen-Weniger and van Veen 1991) and whether artificial inoculation of N 2 -fixing bacteria enhances the growth of cereals (e.g., Boddey et al 1986;Harris et al 1989).…”

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confidence: 99%

Associative N₂-fixation in pearl millet and sorghum: Levels and response to inoculation

Lee

Wani

Yoneyama³

et al. 1994

Soil Science and Plant Nutrition

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Nitrogen fixation by Azospirillium brasilense in soil and the rhizosphere under controlled environmental conditions

Cited by 34 publications

References 41 publications

RETRACTED ARTICLE: Effect of root-zone salinity and form of N on photosynthate partitioning in wheat (Triticum aestivum L.)

RETRACTED ARTICLE: Effect of root-zone salinity and form of N on photosynthate partitioning in wheat (Triticum aestivum L.)

Temporal Dynamics of Abundance and Composition of Nitrogen-Fixing Communities across Agricultural Soils

Associative N₂-fixation in pearl millet and sorghum: Levels and response to inoculation

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Nitrogen fixation by Azospirillium brasilense in soil and the rhizosphere under controlled environmental conditions

Cited by 34 publications

References 41 publications

RETRACTED ARTICLE: Effect of root-zone salinity and form of N on photosynthate partitioning in wheat (Triticum aestivum L.)

RETRACTED ARTICLE: Effect of root-zone salinity and form of N on photosynthate partitioning in wheat (Triticum aestivum L.)

Temporal Dynamics of Abundance and Composition of Nitrogen-Fixing Communities across Agricultural Soils

Associative N2-fixation in pearl millet and sorghum: Levels and response to inoculation

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Associative N₂-fixation in pearl millet and sorghum: Levels and response to inoculation