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Variabilité de l'adaptation à la sécheresse des cèdres méditerranéens (Cedrus atlantica, C. brevifolia et C. libani) : aspects écophysiologiques

Abstract : We have characterized and compared ecophysiological behavior of the Mediterranean cedars (Cedrus atlantica, C. libani and C.brevifolia) and their reaction to drought. The acclimation to drought was realized by submitting half of a lot of three-year-old seedlings to a moderate drought for a long period. The other half was well watered. The effect of a sever drought was studied on seedlings of the two treatments. Several ecophysiological paramelers were studied, on which growth, CO2 assimilation rate (A), stomatal conductance (gs), xylem vulnerability to embolism,thermotolerance of photosystem II (PSII) and carbon isotope composition (delta 13C). C. brevifolia has a weak growth and intrinsic water Use efficiency (WUEi). Its growth and gas exchanges are not very sensitive to drought. On the contrary, C. atlantica has a strong grouth and high WDEi, but also a high drought sensitivity. This species has the most vulnerable xylem to embolism and it has a PSII more sensitive to high ternperatures. C. Libani has intermediate characteristics. The long-period of moderate drought increased the thermotolerance of the PSII. We also studied ecophysiological variability of C. Libani by following and comparing, for 3 years, the biomass, growth and delta 13C of 19 Turkish and Lebanese provenances. The effect of atmospheric drought (VPD) on the gas exchanges was also studied. The height growth, biomass and shoot-leaves/roots ralio as well as delta 13C show higher variability than the response of the gas exchanges to the VPD. The Lebanese provenances are more successful from the point of view of growth. But they seem less adapted to drought than the Turkish provenances. The variability of response to VPD within Turkish C. libani is weak. The decrease of gs and the CO2 net assimilation, which follows the increase of VPD, is stronger in seedlings which are drought acclimatized.
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Submitted on : Thursday, March 29, 2018 - 10:39:02 AM
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Mehdi Ladjal. Variabilité de l'adaptation à la sécheresse des cèdres méditerranéens (Cedrus atlantica, C. brevifolia et C. libani) : aspects écophysiologiques. Sylviculture, foresterie. Université Henri Poincaré - Nancy 1, 2001. Français. ⟨NNT : 2001NAN10215⟩. ⟨tel-01746495⟩



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