40 research outputs found
Physiology, genetics and genomics of drought adaptation in Populus
No full textAs the demand for energy rises, Populus species are increasingly grown as bioenergy crops. Meanwhile, due to global change, predictions indicate that summer droughts will increase in frequency and intensity over Europe. This study was carried out to evaluate the adaptation to drought in Populus, at different levels: genetic, genomics and physiology. Forests trees such as poplar are very important ecologically and economically but the Populus genus is known to be drought sensitive. Consequently, it is essential to understand drought response and tolerance for those trees. Two populations of poplar were used for this study, a mapping population (Family 331) and a natural population of Populus nigra. The F2 mapping population obtained from a cross of Populus deltoides and Populus trichocarpa, showed differences in stomatal conductance and carbon isotope composition in both clones and the F2 progeny. It was also used to discover QTL related to water use efficiency highlighting interesting areas of the genome. Combining QTL discovery and microarray analysis of the two clones in response to drought, a list of candidate genes was defined for water use efficiency. The natural population of Populus nigra consisting of 500 genotypes of wild black poplar showed variation in numerous physiological measurements such as leaf development and carbon isotope discrimination in well-watered conditions depending on their latitude of origin. The drier genotypes (from Spain and South France) had the smallest leaf area which could be linked to an adaptation to drought. Physiological measurements of extreme genotypes in leaf size of this population revealed differences in response to water depending on their latitude of origin. Stomatal conductance rapidly decreased and water use efficiency improved for Spanish genotypes after a slow and moderate drought stress. Direct comparisons between the transcriptome of extreme genotypes from Spain and North Italy in well watered and drought conditions provided an insight into the genomic pathways induced during water deficit. Six candidate genes were selecting for further analysis using real-time PCR: two stomatal development genes (ERECTA and SPEECHLESS), two ABA related genes (ATHVA22A and CCD1), a second messenger (IP3) and a NAC transcription factor (RD26
Toward improved drought tolerance in bioenergy crops: QTL for carbon isotope composition and stomatal conductance in Populus
No full textDedicated non-food bioenergy crops like poplar are needed as sustainable, low-input feedstocks for renewable energy in a future drier climate, where they can be grown on marginal soils. Such plants should have a low water, carbon, and chemical footprint. Capturing natural variation in traits associated with water use efficiency (WUE) is the first step to developing trees that require less water and may be adapted to drier environments. We have assessed stomatal conductance (gs) and leaf carbon isotope composition (?13C, an indirect indicator of leaf WUE) in two Populus species, P. deltoides and P. trichocarpa and their F2 progeny, grown in the United Kingdom and in Italy. Populus deltoides leaves showed lower ?13C than P. trichocarpa, suggesting a higher WUE in P. trichocarpa, although without drought preconditioning, gs of P. trichocarpa was less responsive to dehydration and abscisic acid treatment than P. deltoides, suggesting that leaf anatomy may also contribute to ?13C in Populus. Quantitative trait loci (QTL) were identified for ?13C on eight linkage groups (LG) and two QTL for gs. From these. QTL and differential gene expression in response to drought from microarray data, we focused on three hotspots and identified 23 novel candidate genes on LG VI, X, and XVI. We have begun to unravel the genetic basis of WUE in bioenergy Populus revealing important underpinning data for breeding and improvement in poplar genotypes for a future drier climat
More plant growth but less plant defence? First global gene expression data for plants grown in soil amended with biochar
No full textBiochar is a carbon (C)-rich solid formed when biomass is used to produce bioenergy. This ‘black carbon’ has been suggested as a solution to climate change, potentially reducing global anthropogenic emissions of greenhouse gases by 12%, as well as promoting increased crop growth. How biochar application to soil leads to better crop yields remains open to speculation. Using the model plant Arabidopsis and the crop plant lettuce (Lactuca sativa L.), we found increased plant growth in both species following biochar application. Statistically significant increases for Arabidopsis in leaf area (130%), rosette diameter (61%) and root length (100%) were observed with similar findings in lettuce, where biochar application also increased leaf cell expansion. For the first time, global gene expression arrays were used on biochar-treated plants, enabling us to identify the growth-promoting plant hormones, brassinosteroid and auxin, and their signalling molecules, as key to this growth stimulation, with limited impacts on genes controlling photosynthesis. In addition, genes for cell wall loosening were promoted as were those for increased activity in membrane transporters for sugar, nutrients and aquaporins for better water and nutrient uptake and movement of sugars for metabolism in the plant. Positive growth effects were accompanied by down-regulation of a large suite of plant defence genes, including the jasmonic acid biosynthetic pathway, defensins and most categories of secondary metabolites. Such genes are critical for plant protection against insect and pathogen attack, as well as defence against stresses including drought. We propose a conceptual model to explain these effects in this biochar type, hypothesizing a role for additional K+ supply in biochar amended soils, leading to Ca2+ and Reactive Oxygen Species (ROS) –mediated signalling underpinning growth and defence signalling response
Land-use change to bioenergy: grassland to short rotation coppice willow has an improved carbon balance
No full textThe effect of a transition from grassland to second-generation (2G) bioenergy on soil carbon and greenhouse gas (GHG) balance is uncertain, with limited empirical data on which to validate landscape-scale models, sustainability criteria and energy policies. Here, we quantified soil carbon, soil GHG emissions and whole ecosystem carbon balance for short rotation coppice (SRC) bioenergy willow and a paired grassland site, both planted at commercial scale. We quantified the carbon balance for a 2-year period and captured the effects of a commercial harvest in the SRC willow at the end of the first cycle. Soil fluxes of nitrous oxide (N2O) and methane (CH4) did not contribute significantly to the GHG balance of these land uses. Soil respiration was lower in SRC willow (912 ± 42 g C m?2 yr?1) than in grassland (1522 ± 39 g C m?2 yr?1). Net ecosystem exchange (NEE) reflected this with the grassland a net source of carbon with mean NEE of 119 ± 10 g C m?2 yr?1 and SRC willow a net sink, ?620 ± 18 g C m?2 yr?1. When carbon removed from the ecosystem in harvested products was considered (Net Biome Productivity), SRC willow remained a net sink (221 ± 66 g C m?2 yr?1). Despite the SRC willow site being a net sink for carbon, soil carbon stocks (0–30 cm) were higher under the grassland. There was a larger NEE and increase in ecosystem respiration in the SRC willow after harvest; however, the site still remained a carbon sink. Our results indicate that once established, significant carbon savings are likely in SRC willow compared with the minimally managed grassland at this site. Although these observed impacts may be site and management dependent, they provide evidence that land-use transition to 2G bioenergy has potential to provide a significant improvement on the ecosystem service of climate regulation relative to grassland systems
Insight into the genetic components of community genetics: QTL mapping of insect association in a fast-growing forest tree
No full textIdentifying genetic sequences underlying insect associations on forest trees will improve the understanding of community genetics on a broad scale. We tested for genomic regions associated with insects in hybrid poplar using quantitative trait loci (QTL) analyses conducted on data from a common garden experiment. The F2 offspring of a hybrid poplar (Populus trichocarpa x P. deltoides) cross were assessed for seven categories of insect leaf damage at two time points, June and August. Positive and negative correlations were detected among damage categories and between sampling times. For example, sap suckers on leaves in June were positively correlated with sap suckers on leaves (P<0.001) but negatively correlated with skeletonizer damage (P<0.01) in August. The seven forms of leaf damage were used as a proxy for seven functional groups of insect species. Significant variation in insect association occurred among the hybrid offspring, including transgressive segregation of susceptibility to damage. NMDS analyses revealed significant variation and modest broad-sense heritability in insect community structure among genets. QTL analyses identified 14 genomic regions across 9 linkage groups that correlated with insect association. We used three genomics tools to test for putative mechanisms underlying the QTL. First, shikimate-phenylpropanoid pathway genes co-located to 9 of the 13 QTL tested, consistent with the role of phenolic glycosides as defensive compounds. Second, two insect association QTL corresponded to genomic hotspots for leaf trait QTL as identified in previous studies, indicating that, in addition to biochemical attributes, leaf morphology may influence insect preference. Third, network analyses identified categories of gene models over-represented in QTL for certain damage types, providing direction for future functional studies. These results provide insight into the genetic components involved in insect community structure in a fast-growing forest tre
Land-use change to bioenergy: grassland to short rotation coppice willow has an improved carbon balance
No full textThe effect of a transition from grassland to second-generation (2G) bioenergy on soil carbon and greenhouse gas (GHG) balance is uncertain, with limited empirical data on which to validate landscape-scale models, sustainability criteria and energy policies. Here, we quantified soil carbon, soil GHG emissions and whole ecosystem carbon balance for short rotation coppice (SRC) bioenergy willow and a paired grassland site, both planted at commercial scale. We quantified the carbon balance for a 2-year period and captured the effects of a commercial harvest in the SRC willow at the end of the first cycle. Soil fluxes of nitrous oxide (N2O) and methane (CH4) did not contribute significantly to the GHG balance of these land uses. Soil respiration was lower in SRC willow (912 ± 42 g C m−2 yr−1) than in grassland (1522 ± 39 g C m−2 yr−1). Net ecosystem exchange (NEE) reflected this with the grassland a net source of carbon with mean NEE of 119 ± 10 g C m−2 yr−1 and SRC willow a net sink, −620 ± 18 g C m−2 yr−1. When carbon removed from the ecosystem in harvested products was considered (Net Biome Productivity), SRC willow remained a net sink (221 ± 66 g C m−2 yr−1). Despite the SRC willow site being a net sink for carbon, soil carbon stocks (0–30 cm) were higher under the grassland. There was a larger NEE and increase in ecosystem respiration in the SRC willow after harvest; however, the site still remained a carbon sink. Our results indicate that once established, significant carbon savings are likely in SRC willow compared with the minimally managed grassland at this site. Although these observed impacts may be site and management dependent, they provide evidence that land-use transition to 2G bioenergy has potential to provide a significant improvement on the ecosystem service of climate regulation relative to grassland systems
1812-2012 : Viger, Harper et la République des Maringouins
No full textLa guerre de 1812 entre le Canada et les États-Unis sera commémorée en 2012-2014 par le gouvernement de Stephen Harper. On étudie ici le discours officiel de cette commémoration dans les sites Internet lancés en 2011 à Ottawa. Sous les justifications historiques avancées par le Premier ministre et son ministre du Patrimoine canadien, peuvent se lire des motivations politiques et une idéologie dont on tente ici de cerner les enjeux. L’angle adopté par cette étude est la représentation des Bas-Canadiens de 1812 en 2012, comparée aux témoignages des acteurs de l’époque. Le point de vue de ceux-ci apparaît crypté dans un récit fantaisiste sur « La République des Maringoins », au coeur de la correspondance entre son auteur, Jacques Viger et ses amis Joseph Mermet et William Berczy. Tous trois étaient alors engagés dans les Voltigeurs canadiens, sous les ordres de Charles Michel d’Irumberry de Salaberry, héros de la bataille de Chateauguay.In 2012-2014, the Harper government will commemorate the war of 1812 between Canada and the United Sates. This study examines the official discourse surrounding this commemoration found in the web sites launched in 2011 by Ottawa. Beneath the historical justifications put forward by the Prime Minister and his Heritage Minister lie political motivations and an ideology that are subject to analysis here. The depiction of the inhabitants of Lower Canada in comparison to that of contemporary actors constitutes the approach adopted for this study. The point of view of the latter appears encoded in the storyline of the “Mosquito Republic” which lies at the centre of the correspondence between its author, Jacques Viger, and his friends Joseph Mermet and William Berczy. All three fought for the Canadian Voltigeurs under Charles Michel d’Irumberry de Salaberry’s command, hero of the Battle of Chateauguay
Adaptive mechanisms and genomic plasticity for drought tolerance identified in European black poplar
No full textSummer droughts are likely to increase in frequency and intensity across Europe, yet long-lived trees may have a limited ability to tolerate drought. It is therefore critical that we improve our understanding of phenotypic plasticity to drought in natural populations for ecologically and economically important trees such as Populus nigra L. A common garden experiment was conducted using ?500 wild P. nigra trees, collected from 11 river populations across Europe. Phenotypic variation was found across the collection, with southern genotypes from Spain and France characterized by small leaves and limited biomass production. To examine the relationship between phenotypic variation and drought tolerance, six genotypes with contrasting leaf morphologies were subjected to a water deficit experiment. ‘North eastern’ genotypes were collected at wet sites and responded to water deficit with reduced biomass growth, slow stomatal closure and reduced water use efficiency (WUE) assessed by ?13C. In contrast, ‘southern’ genotypes originating from arid sites showed rapid stomatal closure, improved WUE and limited leaf loss. Transcriptome analyses of a genotype from Spain (Sp2, originating from an arid site) and another from northern Italy (Ita, originating from a wet site) revealed dramatic differences in gene expression response to water deficit. Transcripts controlling leaf development and stomatal patterning, including SPCH, ANT, ER, AS1, AS2, PHB, CLV1, ERL1–3 and TMM, were down-regulated in Ita but not in Sp2 in response to drought
Modern Poets of the Southern Bassarabia
No full textSouthern Bassarabiais is inseparable historically from the active creative
development. Being in the shadow of major cultural centers, the region is not completely separated.
However, it has a certain isolation that allowed to develop the authenticity of the artistic style in the
works of poets of the southern Bassarabia. Representatives of the literary process develop eternal
themes of house, native land, earth, nature, love. At the same time, they open up new horizons of
poetry, use modern technical means to promote their works, put actual topical issues and use nonstandard
means of artistic expression. The author argues that modern poets of Southern Bassarabia are
in a single cultural field with the poets of the Euroregion “Lower Danube”
Comparison of Explicit and Implicit Keywords to Characterize Geographic Information System Procedures
No full textThe author designs and implements an approach that exploits semantically important information that is not ordinarily included in traditional information retrieval approaches to improve the handling of Geographic Information System (GIS) procedural software. In this approach, what are termed here implicit keywords, descriptors designed to recognize characteristics not explicitly recorded within the GIS procedure source code, are created and used in an automated, inductive process to organize a large set of GIS procedures to reveal meaningful groupings. The process uses the Self-Organizing Maps (SOM), a specialized artificial neural network, to create a two-dimensional representation of an input data set wherein topological properties of the input data set are preserved. Such maps are important tools for helping visualize, browse, filter, and evaluate a set of GIS procedures . Browsing, filtering, and evaluation help to improve human understanding of available GIS resources. By facilitating mechanisms for improved software sharing and exchange, the methods described here may guide future researchers in the selection of more appropriate procedures for a given task. Through experiments of this dissertation, the author demonstrates that while using GIS commands as explicit keywords can produce helpful organizations of GIS procedures, development of implicit keywords can be used to moderate, improve, and specialize the results of the explicit keyword process. The results of the different experiments not only show the impacts of applying different keyword schemes, but bear witness to the fact that GIS functionality can be organized with consistent methodological rigor in potentially very different ways to reprioritize specific types of functionality
