| 1. |
|
|
| 2. |
- Alm Carlsson, Gudrun, et al.
(författare)
-
Monte Carlo metoden : ett verktyg inom strålningsfysiken
- 1995
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detta kompendium är tänkt att användas som ett propedeutiskt kursmaterial för kursdeltagare i kursen "Monte Carlo simulering av foton- och elektrontransport vid diagnostiska och radioterapeutiska strålkvaliteter". Först följer en kort repetition av den grundläggande statistik som utnyt1jas i beräkningarna. Därefter följer en beskrivning av slumptal. det fundament som metoden bygger på. Vidare beskrivs val ur olika frekvensfunktioner. Valet kan även göras ur så kallade falska fördelningar för att reducera variansen i den skattade storheten. Metoderna belyses i ett avsnitt om problemlösningsmetodik. först i allmänna termer för att sen gå in på ett specifikt problem (Buffons nålproblem) där en analys och strukturering av problemet görs varefter flödesschema och kodning exemplifieras. Så följer två moment där en beskrivning görs av färderna av fotoner respektive elektroner genom materia. För elektronfärderna gör man en indelning i klass 1- och klass II-färder. Vad detta innebär och hur deltapartiklar tas om hand beskrivs i ett kapitel. Till sist kommer en kort introduktion till de tre laborationerna med laborationshandledningar. Speciell vikt har lagts vid att initiera laboranten att fundera på fysiken i de simulerade experimenten. Detta kompendium har tillkommit som examinationsarbete vid en kurs i "Monte Carlo simulering av foton- och elektrontransport vid diagnostiska och radioterapeutiska strålkvaliteter", med andra ord den kurs du själv nu ämnar studera. Författarna önskar dig lycka till med kursen och hoppas att du kommer att få glädje av den. Speciellt hoppas vi att denna skrift ska underlätta för dig att tillgodogöra dig informationen vid föreläsningarna och under laborationerna.
|
|
| 3. |
|
|
| 4. |
- Bargaz, Adnane, et al.
(författare)
-
Discrimination against N-15 among recombinant inbred lines of Phaseolus vulgaris L. contrasting in phosphorus use efficiency for nitrogen fixation
- 2014
-
Ingår i: Journal of Plant Physiology. - : Elsevier BV. - 0176-1617 .- 1618-1328. ; 171, s. 199-204
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- Bargaz, Adnane, et al.
(författare)
-
Faba bean variety mixture can modulate faba bean-wheat intercrop performance under water limitation
- 2021
-
Ingår i: Frontiers in Agronomy. - : Frontiers Media SA. - 2673-3218. ; 3
-
Tidskriftsartikel (refereegranskat)abstract
- Commercial legume varieties vary in terms of their drought tolerance when grown as sole crops, though relatively little is known about how legume variety selection affects cereal–legume intercrop performance under drought conditions. This study aims to test the hypothesis that positive rhizosphere interactions in faba bean–wheat intercrops will confer a “buffering capacity” on faba bean and wheat performance under water stress and that this effect will (i) depend on faba bean varietal selection and (ii) be enhanced with increasing faba bean varietal diversity. In a greenhouse experiment, three commercial faba bean (Vicia faba L.) varieties [Gloria (G), Alexia (A), Julia (J)] were grown in sole crop or intercropped with spring wheat (Triticum aestivum L.) under well-watered or water-stress conditions. Under intercropping, either one, two, or all three faba bean varieties were grown together with wheat to test the effect of intraspecific diversity on a cereal–legume intercrop performance. Consistent with the proposed hypothesis, we found that, under well-watered and water-stress conditions, wheat and faba bean shoot biomass production and nitrogen (N) acquisition improved with intercropping and that faba bean variety and variety mixture strongly modulated the intercropping effect. Interestingly, in both well-watered and water-stress conditions, wheat dry biomass and N accumulation were greatest in intercrops containing Gloria, while nodule number, nodule weight, and N accumulation in faba bean were greatest for intercrops containing Alexia and Julia (AJ). The effect of varietal diversity was inconsistent. Intercrops with two faba bean varieties tended to have positive or neutral effects on measured wheat and faba bean variables. However, overall performance under intercropping was generally reduced when all three faba bean varieties were planted with wheat. The effect of faba bean species diversity can buffer faba bean–wheat intercrop performance against water stress, and intercropping tended to have positive or neutral effects on the measured wheat and faba bean variables, notably with two-varietal faba bean mixtures.
|
|
| 6. |
- Bargaz, Adnane, et al.
(författare)
-
Intercropping of faba bean with wheat under low water availability promotes faba bean nodulation and root growth in deeper soil layers
- 2015
-
Ingår i: Procedia Environmental Sciences. - : Elsevier BV. - 1878-0296. ; 29, s. 111-112
-
Konferensbidrag (refereegranskat)abstract
- The symbiotically fixed N is advantageous to legumes growing under N-limiting conditions, and is also potentially beneficial for subsequent or associated non-legume crops(1, 2). However, under stressful conditions such as water limitation and low nutrient availability, legumes may lose the distinct advantage of an unlimited source of symbiotic N-2 (3, 4,) (5) Belowground niche complementarity in legume-cereal intercrops may improve resource use efficiency and adaptability to environmental constraints, but effects of water limitation on legume rooting and nodulation patterns is poorly understood. To advance our knowledge of mechanisms involved in water stress response, faba bean (Vicia faba L., FB) and wheat (Triticum aestivum L.) were grown as mono- and intercrops in soil-filled plexiglass rhizoboxes under water sufficiency (80% of field capacity; FC) and water stress (30% of FC). Water stress decreased shoot biomass in both monocropped and intercropped FB, as well as root length in monocropped FB. Intercropping increased both shoot dry weight and height of FB irrespective of water treatment, while increased root biomass and length in intercropped FB was observed only under water stress. No significant effects of crop or water treatment were found on wheat growth parameters. Intercropping increased overall nodulation (nodule number and nodule dry weight; NDW) regardless of water availability. However spatial patterns of nodulation differed between water treatments: top-15-cm NDW and number increased (27 and 33%, respectively) in sufficiently-watered intercropped FE, while NDW in the same soil layer significantly decreased (45%) in water-stressed intercropped FE. In contrast, below-15-cm NDW and number significantly increased in intercropped FE under both water levels. This enhanced nodulation in the deeper soil layer and the associated increase in root and shoot growth provides evidence for a shift in niche occupancy that improves FB performance when exposed to water limitation in intercropping. (C) 2015 The Authors. Published by Elsevier B.V.
|
|
| 7. |
- Bargaz, Adnane, et al.
(författare)
-
Nodulation and root growth increase in lower soil layers of water-limited faba bean intercropped with wheat
- 2016
-
Ingår i: Journal of Plant Nutrition and Soil Science. - : Wiley. - 1436-8730 .- 1522-2624. ; 179, s. 537-546
-
Tidskriftsartikel (refereegranskat)abstract
- Below-ground niche complementarity in legume-cereal intercrops may improve resource use efficiency and root adaptability to environmental constraints. However, the effect of water limitation on legume rooting and nodulation patterns in intercropping is poorly understood. To advance our knowledge of mechanisms involved in water-limitation response, faba bean (Vicia faba L.) and wheat (Triticum aestivum L.) were grown as mono- and intercrops in soil-filled plexiglass rhizoboxes under water sufficiency (80% of water-holding capacity) and water limitation (30% of water-holding capacity). We examined whether intercropping facilitates below-ground niche complementarity under water limitation via interspecific root stratification coupled with modified nodulation patterns. While no significant treatment effects were measured in intercropped wheat growth parameters, water limitation induced a decrease in shoot and root biomass of monocropped wheat. Likewise, shoot biomass and height, and root length of monocropped faba bean significantly decreased under water limitation. Conversely, water limitation stimulated root biomass of intercropped faba bean in the lower soil layer (15-30 cm soil depth). Similarly, total nodule number of faba bean roots as well as nodule number in the lower soil layer increased under intercropping regardless of water availability. Under water limitation, intercropping also led to a significant increased nodule biomass (48%) in the lower soil layer as compared to monocropping. The enhanced nodulation in the lower soil layer and the associated increase in root and shoot growth provides evidence for a shift in niche occupancy when intercropped with wheat, which improves water-limited faba bean performance.
|
|
| 8. |
- Bargaz, Adnane, et al.
(författare)
-
Phosphorus Use Efficiency for N2 Fixation in the Rhizobial Symbiosis with Legumes
- 2015
-
Ingår i: Biological Nitrogen Fixation. - Hoboken, NJ, USA : John Wiley & Sons, Inc. - 9781118637043 ; , s. 455-464
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Symbiotic nitrogen fixation (SNF) by legumes may provide an ecologically acceptable complement or substitute for mineral nitrogen fertilizers that farmers try to minimize for economic limitation and environment sake. However, phosphorus (P) deficiency is a major limiting factor for legume–rhizobia symbioses, particularly in acidic and calcareous soils. Nevertheless, the expression of legume SNF potential under P deficiency may be improved. Indeed genotypes contrasting in P use efficiency (PUE) for SNF could be found for such legumes spp. asPhaseolus vulgaris,Vigna unguiculata, orMedicago truncatulain hydroaeroponic culture under glasshouse conditions after inoculation with specific reference rhizobia. In order to assess the contribution of phosphatase activity to PUE for SNF, anin situRT-PCR methodology was used to localize and quantify the mRNA of candidate genes in nodules of common bean grown under deficient versus sufficient P supply. The transcript localization of phytase, phosphoenolpyruvate phosphatase, and trehalose 6 phosphate phosphatase was found to be tissue specific and differ among any phosphatase APase genes, P treatments, and legume genotypes. In order to assess whether the genotypic difference in PUE for SNF may contribute to adaptation of the rhizobial symbiosis to low-P soils, the nodulation and growth of contrasting common-bean recombinant lines from the cross of BAT477 and DOR364 were assessed in fields of farmers in reference agroecosystems of the Mediterranean basin following a participatory approach. The most efficient genotype, namely RIL115, was superior in most fields where nodulation was above the threshold for significant contribution to legume nutrition. From those fields with low-P soils where adaptation was observed for low-efficiency genotypes, bacteria were isolated from nodules and rhizosphere in order to search for rhizobia or rhizobacteria that could increase the P efficiency for the legume symbiosis. Since mycorrhizae may contribute to the PUE, the tripartite symbiosis was tested in hydroaeroponic culture, showing that some species may limit nodulation by contrast withGlomus intradicesthat increased it under P deficiency. It is concluded that (i) phosphatases contribute to the use of organic P for N2fixation and to the increase in nodule permeability to O2under P deficiency; (ii) nodulation in agroecosystems varies considerably in space and time; (iii) high PUE for SNF may increase the N2-dependent growth of common bean in low-P soils and the overall P bioavailability; and (iv) some local rhizobia may contribute to the PUE for SNF.
|
|
| 9. |
- Bargaz, Adnane, et al.
(författare)
-
Physiological and Molecular Aspects of Tolerance to Environmental Constraints in Grain and Forage Legumes
- 2015
-
Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 16, s. 18976-19008
-
Forskningsöversikt (refereegranskat)abstract
- Despite the agronomical and environmental advantages of the cultivation of legumes, their production is limited by various environmental constraints such as water or nutrient limitation, frost or heat stress and soil salinity, which may be the result of pedoclimatic conditions, intensive use of agricultural lands, decline in soil fertility and environmental degradation. The development of more sustainable agroecosystems that are resilient to environmental constraints will therefore require better understanding of the key mechanisms underlying plant tolerance to abiotic constraints. This review provides highlights of legume tolerance to abiotic constraints with a focus on soil nutrient deficiencies, drought, and salinity. More specifically, recent advances in the physiological and molecular levels of the adaptation of grain and forage legumes to abiotic constraints are discussed. Such adaptation involves complex multigene controlled-traits which also involve multiple sub-traits that are likely regulated under the control of a number of candidate genes. This multi-genetic control of tolerance traits might also be multifunctional, with extended action in response to a number of abiotic constraints. Thus, concrete efforts are required to breed for multifunctional candidate genes in order to boost plant stability under various abiotic constraints.
|
|
| 10. |
- Bargaz, Adnane, et al.
(författare)
-
Species interactions enhance root allocation, microbial diversity and P acquisition in intercropped wheat and soybean under P deficiency
- 2017
-
Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393 .- 1873-0272. ; 120, s. 179-188
-
Tidskriftsartikel (refereegranskat)abstract
- Belowground interactions in grain legume-cereal intercrops may improve resource acquisition and adaptation to environmental constraints such as phosphorus (P) deficiency. To advance the knowledge of belowground facilitative mechanisms involved in P-deficiency tolerance (root allocation, biochemical and microbial responses), soybean (Glycine max) and wheat (Triticum aestivum) were grown as monocrops and intercrops under P-deficiency and P-sufficiency conditions in soil-filled rhizoboxes. The hypothesis was that intercropping stimulates root microbial diversity, root biomass allocation and P-hydrolyzing acid phosphatases (APase) activity in roots under P-deficient conditions. Total root dry weight (RDW), length, and surface area significantly increased in P-deficient intercropped wheat and soybean. Greater root allocation to deeper soil layers was evident for P-deficient intercropped wheat. Shallow roots of intercropped wheat exhibited highly stimulated APase activity under P-deficient conditions while shallow roots of monocropped soybean exhibited higher APase activity in comparison to deeper roots, irrespective of P treatment. Root fungal diversity was significantly (p < 0.05) higher in intercropped wheat, and was significantly correlated with RDW, root APase activity, shoot P, and soil available P (rho = 0.24, p= 0.01). Root bacterial diversity was higher in both intercrops, and was significantly correlated with RDW and shoot N concentration. The observed shifts in root microbial diversity, root biomass allocation and APase activity provide explanatory mechanisms of relationships between rhizosphere heterogeneity and pathways for increased P acquisition in diversified crops. Advanced belowground metabolomics on root microbial communities are required to reveal the beneficial effect of root microorganisms in associations of different crop species.
|
|
