Comparaison interspécifique de la dynamique saisonnière de composés azotés et carbonés chez le chêne sessile (Quercus petraea Matt. Liebl.), le chêne pédonculé (Quercus robur L.) et le hêtre (Fagus sylvatica L.) aux stades juvéniles et adultes : effet de la défoliation et de la lumière sur la gestion des réserves

Abstract : This research allows us to compare the biomass composition in nitrogenous and carbon compounds in three forest tree species. C contents (g / kg biomass) are stable whatever the species and age. N contents (g / kg biomass) are 10 times more in young trees, whatever the species. It has important links between N content and age. The C/N ratio is almost 10 times less in young trees, due to their content of total nitrogen. Stocks for a given age are comparable between species. Starch contributes to total carbon in a more important fraction in young trees: 50 % against 8 % in adult trees. Starch concentration in Quercus robur is more elevated in comparison with Quercus petraea and Fagus sylvatica. This comparison of species, in both youth and adult ages, allowed the evidence of different physiological mechanisms, linked to phenology. This research concerned the characterization of carbon and nitrogenous reserves by difference of present quantities at tree level in two dates corresponding to important phenologic stages. We used the 15N labelling, which allowed partitioning of nitrogen neo-assimilated to nitrogen coming from reserves remobilisation, in young trees defoliated and in different light conditions. Carbon and nitrogen remobilisation of reserves seems to be not synchronous and differed among species: oak renew only 10% of its nitrogen while beech renew 20%. We have characterized a 25kDa polypeptide in the trunk sapwood of Quercus robur, this polypeptide presents all characteristics of a Vegetative Storage Protein (VSP). Limits and uncertainties of methods used during this research are discussed.
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Luis Manuel Valenzuela Nunez. Comparaison interspécifique de la dynamique saisonnière de composés azotés et carbonés chez le chêne sessile (Quercus petraea Matt. Liebl.), le chêne pédonculé (Quercus robur L.) et le hêtre (Fagus sylvatica L.) aux stades juvéniles et adultes : effet de la défoliation et de la lumière sur la gestion des réserves. Biologie végétale. Université Henri Poincaré - Nancy 1, 2006. Français. ⟨NNT : 2006NAN10177⟩. ⟨tel-01748627⟩

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