Báo cáo lâm nghiệp: "Field studies of leaf gas exchanges (Elaeis guineensis Jacq.)"

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in oil Field studies of leaf gas palm tree exchanges (Elaeis guineensis Jacq.) E. Dufrene B. Saugier Orsay Cedex, France d’Ecologie V6g6tale, Universit6 Paris-Sud, 91405 Laboratoire In this study, we evaluated variations in Introduction leaf photosynthesis in 8 trees of the same progeny, and the effect of vapor pressure This study is part of a larger research pro- deficit (VPD e (T e and leaf tem- saa) -) = gram on climatic and biological factors perature ( T on stomatal conductance and ) t affecting oil palm yield. Our purpose was leaf gas exchanges. to characterize, under conditions of good water supply, variations in leaf photosyn- thesis with internal and external factors. Materials and Methods Several authors have been working on study site was located at the The the C0 assimilation rate (A) in oil palm. 2 LR.H.O. experimental station of La 2 C.LR.A.D. V Most of them have used young plants Me near Abidjan, Ivory Coast (5°26’N Lat., under laboratory conditions to study 3°50’W Long.). The studied trees belong to one effects of photosynthetically active radia- single line (L2T used as a reference in D10D) * many trials of the production area and char- tion (Corley et al., 1973; Hirsch, 1975), acterized by a moderate vegetative develop- foliar temperature (Hong and Corley, ment associated with good bunch production. 1976) or leaf water potential and stomatal The net C0 assimilation rate (A) was mea- 2 conductance (Adjahossou, 1983). Only 2 sured using a leaf chamber (PLC, A.D.C.3) and experiments were conducted in the field: a portable C0 analyzer (LCA2, A.D.C.) 2 connected in an open system. Leaf tempera- Bolle-Jones (1968) determined the ture, transpiration rate, boundary layer and sto- amount of soluble sugars in 9 yr old leaf- matal conductances were calculated using the lets and Corley (1983) observed the energy balance equation (Parkinson, 1985) effects of leaf senescence on photosyn- combined with standard equations (von Caem- merer and Farquhar, 1981 thesis using the 14 method. 2 CO ). 1 RI.R.H.O.: L Institut de Recherche .H.O.: les Huiles et les 01, 6agineux. 0 [6agineux. sur 2 C.I.R.A.D.: Centre de Cooperation International en Recherche Agronomique pour le D6veloppement. 3 A.D.C.: Analytical Development Company.
Results conductance increased with leaf tempera- (Fig. 3c, cl). ture 1 shows measurements made on the Fig. 8th 9th leaf of 8 different palm trees or (last leaf fully opened is numbered 1 ). Discussion and Conclusion Light was the only limiting factor. Relative error of measurements in low light was too The maximal photosynthesis observed in high to allow a comparison of apparent 5 yr old oil palm (A 23.70 !rmol!m-2!s-!) = quantum yield between trees. was not very different from Corley’s (1983) Maximal leaf assimilation rates (PAR 20 p 3 yr old -S-1, 2 ol-M- M results (A = higher than 1100 pmol were not ) 1 s 2 m- ’ trees, leaf number 10). This high C0 2 significantly different between trees (F= 1, assimilation rate is quite similar to those of dF= 52). fast growing temperate trees, such as The maximal C0 assimilation rate 2 Populus sp. ((:eulemans et aL, 1987) and decreased with leaf age in 10 yr old oil slightly higher than those of wet tropical palm (Fig. 2). This decrease became more forest and crop trees (Mooney et aL, 1984. pronounced at leaf number higher than 25 Leaf temperature between 30 and 38°C (= 2 yr old), when maximal stomatal had no effect on photosynthesis which conductance was also decreasing. shows an adaptation to high temperatures in this tropical C species. 3 The net assimilation rate was 2 C0 Observed stomatal opening with in- to VPD increase up to slightly sensitive creases in temperature is a classical re- kPa, and then it dropped steadily (Fig. 1.7 sponse that is often concealed by a simul- 3a). The transpiration rate decreased taneous variation in VPD (Jarvis and linearly with VPD because of rapid stoma- Morison, 1981).When VPD increases tal closing (Fig. 3a, b). There was no above about 1 kPa, it causes a rapid sto- change in the C0 assimilation rate as a 2 matal closure that induces a decrease in result of changes in leaf temperature (Fig. the transpiration rate, despite a high eva- 3c). The transpiration rate and stomatal
Ceulemans R., Impens 1. & Steenackers V. porative demand. Stomatal sensitivity to (1987) Variations in photosynthetic, anatomical VPD has been reported in numerous spe- and enzymatic leaf traits and correlations with cies (Farquhar et aL, 1980; El Sharkawy in recently selected growth Populus hybrids. et al., 1984). It is especially pronounced in Can. J. For. Res. 17, 273-283 oil palm and confers good survival Corley R.H.V. (1983) Photosynthesis and age of capability to overcome drought to this spe- oil palm leaves. Photosynthetica 17, 97-100 cies but strongly reduces bunch produc- Corley R.H.V., Hardon J.J. & Ooi S.C. (1973) tion. Some evidence for genetically controlled varia- tion in photosynthetic rate of oil palm seedlings. Euphytica 22, 48-55 EI-Sharkawy M.A., Cock J.H. & Held A.A.K. References (1984) Water use efficiency of cassava. 11. Dif- fering sensitivity of stomata to air humidity in cassava and other warm-climate species. Crop D.F. (1983) Contribution a I’dtude Adjahossou Sci. 24, 505-507 de la resistance a la s6cheresse chez le pal- mier a huile (Elaeis guineensis Jacq.) Ph.D. Farquhar G.D., Schulze E.D. & Kuppers M. Thesis, Université Paris VII, France (1980) Responses to humidity by stomata Nicotiana glauca L. and Corylus avellana L. are Bolle-Jones E.W. (1968) Variations of chloro- consistent with the optimization of carbon diox- phyll and soluble sugar in oil palm leaves in ide uptake with respect to water loss. A J. relation to position, time of day and yield. Olea- usf. Plant Physiol. 7, 3i 5-327 gineux 23, 505-511 l
Mooney H.A., Field C. & Vasquez-Yanes C. Hirsch P.J. (1975) Premiers travaux sur I’assimi- (1984) Photosynthetic characteristics of wet lation photosynth6tique du palmier huile tropical forest plants. In: Physiological Ecology (Elaeis guineensis Jacq.). Thesis, ORSTOM- of Plants of the Wet Tropics. (Medina E., et al., RHO, La M6, Ivory Coast eds.), Dr. W. Junk Pubi., The Hague, pp. 113- Hong T.K. & Corley R.H.V. (1976) Leaf 128 temperature and photosynthesis of a tropical C3 (1985) A simple method for Parkinson K.J. plant Elaesis guineensis. Mardi Res. Bull. 4, 16- determining boundary layer resistance in leaf 20 cuvettes. Plant Cell Environ. 8, 223-226 Jarvis P.G. & Morison J.I.L. (1981) Stomatal Caemmerer S. & Farquhar G.D. (1981) control of transpiration and photosynthesis. In: von Some relationships between the biochemistry of Stomatal Physiology. (Jarvis P.G. & Mansfield photosynthesis and the gas exchange of T.A., eds.), Cambridge Univ. Press, Cambridge, leaves. Planta 153, 376-387 pp. 247-279