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Báo cáo lâm nghiệp: "resistance of two Douglas fir species (Pseudotsuga menziesii (Mirb.) Franco and Pseudotsuga macrocarpa (Torr.) Mayr.): relative importance of water use efficiency and root growth potentia"

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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...

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Nội dung Text: Báo cáo lâm nghiệp: "resistance of two Douglas fir species (Pseudotsuga menziesii (Mirb.) Franco and Pseudotsuga macrocarpa (Torr.) Mayr.): relative importance of water use efficiency and root growth potentia"

resistance of two Douglas fir species (Pseudo- Drought tsuga menziesii (Mirb.) Franco and Pseudotsuga macro- carpa (Torr.) Mayr.): relative importance of water use efficiency and root growth potential J.M. Guehl G. Aussenac, P. Grieu Laboratoire de Bioclimatologie et Ecophysiologie Forestière, Station de et de Produc- Sylviculture tion, INRA Centre de Nancy, Champenoux, 54280 Seichamps, France ! Introduction maintained at 4.6 Pa!KPa-!, and 2) in response to increasing d4V in well-watered plants. The measurements were performed with an assimi- In order to optimize the choice of species lation chamber in which air temperature, ambient C0 concentration, photosynthetic 2 for reforestation in regions subjected to photon flux density and water vapor pressure summer water shortage, it is important to were controlled. Analyzing the data trough A determine which physiological compo- vs Intracellular C0 molar fraction (Ci) graphs, 2 nents may be involved in their drought could determine stomatal and mesophyll we components of changes in A (Prioul et al., adaptation. Therefore, we have carried out 1984; Jones, l!185). The gas exchange re- this study aimed at comparing the ecophy- sponse to zH!Vwas also examined with respect siological behavior of 2 Douglas fir spe- the optimization theory of Cowan and to cies: Pseudofsuga menziesii (Mirb.), origi- Farquhar (1977). nating from a relatively wet coastal In a second experiment (Grieu and Ausse- zone (Ashford, WA, U.S.A., 300 m eleva- nac, 1988), non-destructive measurements of the number of growing roots and root elonga- tion) and Pseudotsuga macrocarpa (Torr.) tion were made on 3 mo old seedlings of the 2 Mayr., growing under drier conditions (CA, species grown in root boxes. U.S.A., 1315 m elevation). Results Materials and Methods Data of Fig. 1 a show that the peak rates of Carbon dioxide assimilation rate (A), stomatal conductance (g! and transpiration rate (E) A were higher in P. menziesii than in were measured on 2 yr old seedlings: 1) during P. macrocarpa. After an initial increase, a soil water depletion cycle (the water status of mesophyll photosynthesis remained un- the plants was determined by predawn water changed over a wide predawn water potential measurements), while the leaf-to-air water vapor pressure difference (4 W) was potential range in both species, while g s
reduced. At higher soil drought, a dra- was matic decline of mesophyll photosynthesis was noted starting from -1.5 MPa in P. macrocarpa and -1.9 MPa in P. menzie- sii. In both species, stomatal conductance and especially mesophyll photosynthesis were dramatically decreased, as d W was increased (Fig. 1 b). P. macrocarpa had the highest and the most unstable - and thus non-optimal values of aEf7A in response to in- - creasing AW (Fig. 2a). P. macrocarpaalso had the highest c7Elc?A at high water poten- tial (Fig. 2b). Growth of the pre-existent roots was more important in P. macrocarpa than in P. menziesii and growth of the new roots was similar in both species (Fig. 3). Furthermore, P. macrocarpa explored the deep soil layers more quickly tha P. men- ziesii (Fig. 4.). Conclusions exchange rates and exhibited the gas least conservative water economy. Unexpectedly, in the present comparative The P. high drought adaptation of study the results show that the drought- resistant P. macrocarpa had the lowest macrocarpa seems to be due mainly to 80 n - fI
menziesii, Pseudotsuga macrocarpa et Cedrus and soil efficient root growth exploration atlantica. Ann. Sci. For. 45, 117-124 abilities, whereas, surprisingly, no adapta- Grieu P., Guehl J.M. & Aussenac G. (1988) The tion features have seem to developed at effects of soil and atmospheric drought on pho- the leaf level. tosynthesis and stomatal control of gas ex- change in three coniferous species. Physiol. Plant. 73, 97-104 References Jones H.G. (1985) Partitioning stomatal and non-stomatal limitations to photosynthesis. Plant Cell Environ. 8, 95-104 Cowan LR. & Farquhar G.D. (1977) Stomatal Prioul J.L., Comic G. & Jones H.G. (1984) Dis- function in relation to leaf metabolism and envi- cussion of stomatal and non-stomatal compo- ronment. Symp. Soc. Exp. BioL 31, 471-505 nents in leaf photosynthesis decline under Grieu P. & Aussenac G. (1988) Croissance et stress conditions. In: Advances in Photosyn- du systbme racinaire de semis thesis Research (Sybesma C., ed.), vol. IV, Mar- d6veloppement de trois esp6ces de conif6res: Pseudotsuga tinus Nijhoff/W. Junk, The Hague, pp. 375-378

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