Rponses adaptatives un asschement daphique chez trois provenances de Chne lige (Quercus suber L.)

Les effets du changement climatique induisent dans la rgion mditerranenne la recrudescence d’vnements extrmes comme la scheresse accentuant la dgradation des cosystmes forestiers de Quercus suber L. Des jeunes plants de trois provenances tunisiennes de Quercus suber (EF, BM et OZ) ont t valus pour leur tolrance au manque d’eau en les soumettant durant 90 jours trois rgimes hydriques (S0 : irrigation 100 % de la capacit au champ (CC), S1 : 50 % CC et S2 : 25% CC). De nombreuses variables ont t mesures (croissance des tiges, surface foliaire, densit et dimension des trichomes et des stomates, changes gazeux et concentration en chlorophylles). Le dficit hydrique a occasionn une rduction des variables cophysiologiques et une augmentation de la densit des stomates et des trichomes. Une variabilit intraspcifique a t enregistre. Les plants EF et BM ont montr un indice de plasticit phnotypique suprieur celui des plants OZ. La meilleure flexibilit vis--vis du stress hydrique s’est traduite chez les plants EF par une augmentation de l’EUEi convertie en une croissance plus soutenue des tiges. Dans un contexte global de rchauffement climatique et de fragilit des forts mditerranennes, la russite des nouveaux boisements de Quercus suber exige le choix de provenances les plus adaptes la faible disponibilit en eau l’instar de la provenance EF. The effects of climate change induce the increase of extreme events such as drought in the Mediterranean region, accentuating the degradation of forest ecosystems of Quercus suber L. Seedlings of Quercus suber (EF, BM and OZ) from three Tunisian provenances were evaluated for their tolerance to water shortage by subjecting them for 90 to three water regimes (S0: irrigation at 100% of the field capacity (FC), S1: 50% FC and S2: 25% FC) for 90 days. Several variables were measured (stem growth, leaf area, trichome and stomatal density and size, gas exchange and chlorophyll concentration). The moisture deficit caused a decrease in ecophysiological variables and an increase in stomata and trichomes density. Intraspecific variability was recorded. EF and BM plants showed a higher phenotypic plasticity index than OZ plants. The better flexibility towards hydric stress was reflected in the EF plants by an increase of the WUEint converted into a more sustained stem growth. In the overall context of global warming and of Mediterranean forests fragility, the success of new afforestation of Quercus suber requires the selection of the best adapted provenances to low water availability, such as the EF provenance

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