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Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: resistance of two Douglas fir species (Pseudotsuga menziesii (Mirb.) Franco and Pseudotsuga macrocarpa (Torr.) Mayr.): relative importance of water use efficiency and root growth potential. | 384s Ann. Sci. For. 1989 46 suppl. 384s-387s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Drought resistance of two Douglas fir species Pseudo-tsuga menziesii Mirb. Franco and Pseudotsuga macro-carpa Torr. Mayr. relative importance of water use efficiency and root growth potential G. Aussenac p. Grieu and J.M. Guehl Laboratoire de Bioclimatologie et Ecophysiologie Forestière Station de Sylviculture et de Production INRA Centre de Nancy Champenoux 54280 Seichamps France Introduction In order to optimize the choice of species for reforestation in regions subjected to summer water shortage it is important to determine which physiological components may be involved in their drought adaptation. Therefore we have carried out this study aimed at comparing the ecophy-siological behavior of 2 Douglas fir species Pseudotsuga menziesii Mirb. originating from a relatively wet coastal zone Ashford WA U.S.A. 300 m elevation and Pseudotsuga macrocarpa Torr. Mayr. growing under drier conditions CA U.S.A. 1315m elevation . maintained at 4.6 Pa KPa-1 and 2 in response to increasing AW in well-watered plants. The measurements were performed with an assimilation chamber in which air temperature ambient co2 concentration photosynthetic photon flux density and water vapor pressure were controlled. Analyzing the data trough A vs Intracellular co2 molar fraction Cj graphs we could determine stomatai and mesophyll components of changes in A Prioul et al. 1984 Jones 1985 The gas exchange response to AW was also examined with respect to the optimization theory of Cowan and Farquhar 1977 . In a second experiment Grieu and Ausse-nac 1988 non-destructive measurements of the number of growing roots and root elongation were made on 3 mo old seedlings of the 2 species grown in root boxes. Materials and Methods Carbon dioxide assimilation rate A stomatai conductance fas and transpiration rate E were measured on 2 yr old seedlings 1 during a soil water depletion cycle the water status
