Variabilité génétique et plasticité de l'efficience d'utilisation des ressources (eau et azote) chez les salicaceae cultivées en taillis à courte et à très courte rotation

Abstract : This work aimed (1) at characterizing the impact of planting density (PD) and pedoclimatic conditions (sites) on the physiology of poplar and willow dedicated to biomass production, (2) at evaluating the genetic variability of productivity-related traits, water-use efficiency (WUE) and nitrogen-use efficiency (NUE) in a perspective of plant breeding, and (3) at assessing the relationships among these traits. Four experimental plantations were established in northern France. Our results show that PD affects biomass production and WUE depending on sites. Under most favorable growth conditions, trees grown at higher density displayed taller stems, lower stem circumference, and lower WUE, than trees grown at lower density indicating that increased tree density mainly accentuated competition for light. Under less favorable conditions, an increase of PD involved higher WUE and lower stem circumference, likely because of an increased competition for water. Positive links between biomass production and WUE were detected for poplar and willow under environmental conditions where competition for resources was reduced. A large canopy is associated to potentially more important transpiration water losses at plant level. This could be compensated at leaf level through a better stomatal regulation. The absence of antagonism between biomass production, WUE, and NUE suggests the possibility to select genotypes for these three traits independently. Moreover, the Genotype x Site interactions indicated the difficulty to identify good genotypes for a large set of site conditions suggesting that the selection has to be realized depending on the site conditions
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Julien Toillon. Variabilité génétique et plasticité de l'efficience d'utilisation des ressources (eau et azote) chez les salicaceae cultivées en taillis à courte et à très courte rotation. Sciences agricoles. Université de Lorraine, 2013. Français. ⟨NNT : 2013LORR0096⟩. ⟨tel-01749868⟩

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