Báo cáo lâm nghiệp: "Environmental control of CO assimilation rate and leaf 2 conductance in two species of the tropical rain forest of French Guiana (Jacaranda copaia D. Don and Eperua falcata Aubl.)"

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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: Environmental control of CO assimilation rate and leaf 2 conductance in two species of the tropical rain forest of French Guiana (Jacaranda copaia D. Don and Eperua falcata Aubl.)...

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Nội dung Text: Báo cáo lâm nghiệp: "Environmental control of CO assimilation rate and leaf 2 conductance in two species of the tropical rain forest of French Guiana (Jacaranda copaia D. Don and Eperua falcata Aubl.)"

Environmental control of CO assimilation rate and leaf 2 conductance in two species of the tropical rain forest of French Guiana (Jacaranda copaia D. Don and Eperua falcata Aubl.) J.M. Guehl 2 1 R. Huc 1 Station de Recherches Forestières, INRA, BP 709, 97387 Kourou Cedex, and Laboratoire 2 de Bioclimatologie-Ecophysiologie, Station de Sylviculture et Production, INRA, Centre de 54280 Seichamps, France Nancy, Champenoux, in French Guiana (53° W, 5.2° N) with 2200 mm Introduction average annual rainfall. Total rainfall over the experimental period (1 September-15 October The potential environmental limitations to 1987) amounted to 67.8 mm, extreme air tem- forest tree production under subequatorial peratures were 20 (night) and 34°C (day) and average potential evapotranspiration was 4.0 climatic conditions are not well under- mm!d-!. The mean height of the studied trees stood. Despite important annual precipita- was 3.6 m (J. copaia) and 2.4 m (E. falcata). In tion, drought in the atmosphere and in the situ C0 assimilation rate (A) and leaf conduc- 2 soil is likely to play a limiting role, tance (g) were determined by means of a port- because: 1) significant climatic water defi- able gas-exchange measurement system (Li- Cor 6200; LI-COR, Lincoln, NE, U.S.A.). Prior to cits occur during the dry seasons; and 2) the measurements reported here, the within- the rain forest species do not seem to tree variability of gas exchange was assessed have evolved efficient adaptative features and was shown to be related to the position of against drought (Doley et al., 1987). The the whorls on the main orthotropic stem in J. present study was aimed at comparing the copaia and to the position of the leaves on the C0 assimilation and stomatal conduc- plagiotropic branches in E. falcata. The data 2 hereafter refer to the zone of maximum A and tance behavior under natural conditions g. Leaf water potential values were determined during the dry season in artifical 3 yr old with a Scholander pressure bomb. stands of J. copaia, a long living pioneer species occurring in open sites, and of E. falcata, a common species of the mature forest canopy. Results and Discussion The 2 species exhibited fundamentally dif- ferent patterns of daily courses of A vs Materials and Methods photosynthetic photon flux density U as ) p is shown for a typical cloudless day in the The study was performed at an experimental site of the Centre Technique Forestier Tropical beginning of the dry season in Fig. 1. With
the exception of leaflet 12, E. falcata was diurnal changes in A in the J. copaia leaf- characterized by daily changes in A being lets were clearly related to the changes in close relationship with those in /p, while of leaf-to-air water vapor pressure dif- J. copaia exhibited a diurnal pattern with a ference (Aw), these latter being closely clear depression of A during the after- associated with the variations of leaf tem- Midday depression entirely perature (Fig. 3). It is not possible here to cannot noon. be taken into account by the concurrent disentangle the possibly colimiting effects of dw and hig temperatures on A. But it stomatal closure, since in the J. copaia h l leaflets, A decreased at constant, or even is worth noting that, in a similar situation, slightly increasing, calculated intercellular Schulze et ai’(1974) provided evidence C0 concentrations (Fig. 2), thus indicat- 2 for d being the factor responsible for w ing that the changes in A are primarily due decreasing A in Prunus armeniaca, a spe- to alterations of mesophyll photosynthesis cies growing in the Negev desert. Effects (Jones, 1985). of Aw on mesophyll photosynthesis inde- pendent of leaf water status alterations The midday depression of A in J. were also observed by Tenhunen et al. copaia was not related to the diurnal (1987) and by Grieu ef al. (1988). changes of leaf water potential (data not reported here). This is in good agreement The two species also responded dif- with the findings of Kuppers et al. (1986) to the soil water depletion cycle ferently which showed the absence of any role of occurring during the dry season, with the leaf water status in explaining the after- gas exchange of E. falcata remaining noon depression of A in a range of spe- unaffected (Fig. 4), whereas both A and g cies of the temperate zone. In fact, the were markedly reduced in J. copaia.
Surprisingly, in the present study, the References typical forest species E. falcata exhibited Doley D., Yates D.J. & Unwin G.L. (1987) Pho- greater drought adaptation features than tosynthesis in an Australian rain forest tree. the pioneer J. copaia. This might be of Argyrodendron peralatum, during the rapid major importance for the choice of appro- development and relief of water deficits in the priate species for reforestation. dry season. Oecologia (Berlin) 74, 441-450
Grieu P., Guehl J.M. & Aussenac G. (1988) The assimilation and intercellular carbon dioxide effects of soil and atmospheric drought on pho- concentration are; not related to leaf water tosynthesis and stomatal control of gas ex- potential. Oecologia (Berlin) 69, 477-480 change in three coniferous species. PhysioL Schulze E.D, Lange O.L., Everani M., Kappen Plant. 73, 97-104 L. & Buschbom U. (1974) The role of air humidi- Jones H.G. (1985) Partitioning stomatal and ty and leaf temperature in controlling stomatal non-stomatal limitations to photosynthesis. resistance of Prunus armeniaca L. under desert Plant Cell Environ. 8, 95-104 conditions I. A simulation of the daily time Kuppers M., Matyssek R. & Schulze E.D. course of stomatal resistance. Oecologia 17, (1986) Diurnal variations of light saturated C0 159-170 2
Tenhunen J.D., Pearcy R.W. & Lange O.L. Stomatal Function (Zeiger E., Farquhar G.D. & (1987) Diurnal variations in leaf conductance Cowan I.R., eds.), Stanford University Press, and gas exchange in natural environments. In: Stanford, pp. 323-351