| 1. |
- Bargaz, Adnane, et al.
(author)
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Discrimination against N-15 among recombinant inbred lines of Phaseolus vulgaris L. contrasting in phosphorus use efficiency for nitrogen fixation
- 2014
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In: Journal of Plant Physiology. - : Elsevier BV. - 0176-1617 .- 1618-1328. ; 171, s. 199-204
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Journal article (peer-reviewed)abstract
- Although isotopic discrimination processes during nitrogen (N) transformations influence the outcome of N-15 based quantification of N-2 fixation in legumes, little attention has been given to the effects of genotypic variability and environmental constraints such as phosphorus (P) deficiency, on discrimination against N-15 during N-2 fixation. In this study, six Phaseolus vulgaris recombinant inbred lines (RILs), i.e. RILs 115, 104,34 (P deficiency tolerant) and 147, 83, 70 (P deficiency sensitive), were inoculated with Rhizobium tropici CIAT899, and hydroaeroponically grown with P-sufficient (250 mu mol P plant(-1) week(-1)) versus P-deficient (75 mu mol P plant(-1) week(-1)) supply. Two harvests were done at 15 (before nodule functioning) and 42 (flowering stage) days after transplanting. Nodulation, plant biomass, P and N contents, and the ratios of N-15 over total N content (N-15/Nt) for shoots, roots and nodules were determined. The results showed lower N-15/Nt in shoots than in roots, both being much lower than in nodules. P deficiency caused a larger decrease in N-15/Nt in shoots (-0.18%) than in nodules (-0.11%) for all of the genotypes, and the decrease in shoots was greatest for RILs 34 (-0.33%) and 104 (-0.25%). Nodule N-15/Nt was significantly related to both the quantity of N-2 fixed (R-2= 0.96***) and the P content of nodules (R-2= 0.66*). We conclude that the discrimination against N-15 in the legume N-2-fixing symbiosis of common bean with R. tropici CIAT899 is affected by P nutrition and plant genotype, and that the N-15/Nt in nodules may be used to screen for genotypic variation in P use efficiency for N-2 fixation. (C) 2013 Elsevier GmbH. All rights reserved.
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| 2. |
- Carlsson, Georg, et al.
(author)
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Alternativa skötselmetoder för ängs- och betesmarker och användning av skördat växtmaterial
- 2014
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Reports (other academic/artistic)abstract
- Ängs- och betesmarker utgör unika livsmiljöer och är mycket värdefulla för den biologiska mångfalden. I dagsläget är utmaningarna stora i Sverige för att kunna hävda ängs- och betesmarkerna med hög kvalitet, till stor del beroende på det minskande antalet betesdjur och minskat behov av fodermarker. Denna rapport sammanställer aktuell kunskap kring möjliga nya skötselmetoder för våra ängs- och betesmarker samt hur skördat material kan användas som en resurs i samhället. Sammanställningen bygger på vetenskaplig och populärvetenskaplig litteratur, författarnas erfarenheter inom området, samt information om pågående teknikutveckling och praktisk tillämpning. Utmaningarna för att utveckla hävden av ängs- och betesmarker består i huvudsak i att hitta rationella system, dels för hantering av betesdjur och dels för effektiv insamling och användning av biomassa. Vi har identifierat följande skötselmetoder och användningsområden som särskilt intressanta för vidare analyser: 1. Flexibel hävd genom till exempel extensivt bete, varierad hävd genom olika skötselmetoder olika år (hävdföljd), kombination av olika metoder genom till exempel maskinell skörd och bränning eller slåtter i kombination med bete. 2. Maskinanpassad hävd av skogsbeten och lövängar – kombinationen av ängsväxter och träd för såväl biologisk mångfald som kolinlagring och produktion av biomassa (både gräs och träd). 3. Småskalig och situationsanpassad teknik – slåtter och borttransport av biomassa från små och hinderrika fält genom en kombination av motormanuella och rationella lösningar. Detta kräver viss metodutveckling och logistik lämpad för avslagning, uppsamling och transport. 4. Samordning och utveckling av avsättning för biomassan för bioenergiändamål. Användning av ängsbiomassa som biogassubstrat har särskilt stor miljönytta och möjliggör effektivt resursutnyttjande genom att man både utvinner energi och en växtnäringsrik rötrest (biogödsel) samtidigt som markerna hävdas. Flera nya studier visar på små eller inga skillnader när slåtter genomförs med skärande eller klippande redskap (lie och knivslåtterbalk) jämfört med roterande redskap (rotorslåttermaskiner med vassa knivar eller röjsnöre). Denna kunskap öppnar upp för maskinell skötsel av slåtterängar som annars hotas av utebliven hävd.
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| 3. |
- Carlsson, Georg, et al.
(author)
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Does nitrogen transfer between plants confound N-15-based quantifications of N-2 fixation?
- 2014
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In: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 374, s. 345-358
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Journal article (peer-reviewed)abstract
- Transfer of fixed N from legumes to non-legume reference plants may alter the N-15 signature of the reference plant as compared to the soil N available to the legume. This study investigates how N transfer influences the result of N-15-based N-2 fixation measurements.We labelled either legumes or non-legumes with N-15 and performed detailed analyses of N-15 enrichment in mixed plant communities in the field. The results were used in a conceptual model comparing how different N transfer scenarios influenced the N-15 signatures of legumes and reference plants, and how the resulting N-2 fixation estimate was influenced by using reference plants in pure stand or in mixture with the legume.Based on isotopic signatures, N transfer was detected in all directions: from legume to legume, from legume to non-legume, from non-legume to legume, from non-legume to non-legume. In the scenario of multidirectional N transfer, N-2 fixation was overestimated by using a reference plant in pure stand.Fixed N transferred to neighbouring reference plants modifies the N-15 signature of the soil N available both to the reference plant and the N-2-fixing legume. This provides strong support for using reference plants growing in mixture with the legumes for reliable quantifications of N-2 fixation.
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| 4. |
- Carlsson, Georg
(author)
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Legume Performance and Nitrogen Acquisition Strategies in a Tree-Based Agroecosystem
- 2014
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In: Agroecology and Sustainable Food Systems. - : Informa UK Limited. - 2168-3565 .- 2168-3573. ; 38, s. 686-703
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Journal article (peer-reviewed)abstract
- Legume N-2 fixation is a critical plant-mediated nutrient pathway highly dependent on site and management conditions, yet little is known of annual crop N-2 fixation associated with established trees in tree-based intercropping systems. Our objective was to investigate the performance and N acquisition strategies of soybean in a tree-based intercropping system with four tree species (genera Juglans, Fraxinus, Acer, and Populus) at two distances from the tree row (1- and 4-m tree-crop interface) in comparison to monocropped soybean. Soil nitrification rates were inversely related to soybean nodule production at the 1-m tree-crop interface (r = -0.64; p = 0.0260). However, regardless of inhibited nodule production, soybeans at the 1-m tree-crop interface were fixing N at high rates as compared to monocropped soybeans, possibly stimulated by belowground interspecies competition; nitrogen derived from atmosphere (Ndfa) in soybeans was highest when intercropped with spruce (75% Ndfa) and poplar (65% Ndfa) at the 1- and 4-m tree-crop interface, respectively. We show a shift in crop N acquisition strategies, as modified by tree species and distance. We suggest that an often overlooked nutrient pathway, nitrate deposition via tree canopy wash, may be an unaccounted abiotic factor influencing nodule formation of associated legume crops.
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| 5. |
- Carlsson, Georg
(author)
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Odlingssystem
- 2014
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In: Växtskyddets grunder. - 9789157692399 ; , s. 14-19
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Book chapter (other academic/artistic)
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| 6. |
- Carlsson, Georg
(author)
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Phosphorous deficiency decreases nitrogenase activity but increases proton efflux in N-2-fixing Medicago truncatula
- 2011
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In: Plant Physiology and Biochemistry. - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 49, s. 458-460
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Journal article (peer-reviewed)abstract
- Effects of Sinorhizobium strain and P nutrition on N-2-dependent growth, nitrogenase activity and proton efflux by nodulated roots were investigated in the model legume Medicago truncatula cultivar Jemalong grown in hydroaeroponic culture in symbioses with Sinorhizobium meliloti strains 102F51 and 2011. Sinorhizobium strain had strong effects on nitrogenase activity and N-2-dependent growth, with S. meliloti 102F51 being the more efficient strain. Apparent and total nitrogenase activities, measured by hydrogen evolution in air and argon, respectively, were drastically reduced in plants supplied with 5 mu mol P plant(-1) week(-1) as compared with 15 mu mol P plant(-1) week(-1). There was a net proton efflux as soon as 2 weeks after inoculation and, in contrast to the effect of P nutrition on nitrogenase activity, P deficiency increased total and specific proton effluxes, irrespective of Sinorhizobium strain. (C) 2011 Elsevier Masson SAS. All rights reserved.
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