Báo cáo lâm nghiệp: "Direct effects of acidic wet deposition on photosynthesis and stomatal conductance of two Populus clones (P. cv. Beaupré and P. cv. Robusta"

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Nội dung Text: Báo cáo lâm nghiệp: "Direct effects of acidic wet deposition on photosynthesis and stomatal conductance of two Populus clones (P. cv. Beaupré and P. cv. Robusta"

Direct effects of acidic wet deposition on photosynthesis and stomatal conductance of two Populus clones (P. cv. Beaupré and P. cv. Robusta) C. Martens K. Landuydt I. Impens Department of Biology, University of Antwerp (U.LA.), Universiteitsplein 1, B-2610 Wilrijk (Antwer- pen), Belgium index (i.e., different leaf plastochron (LPI)). Introduction obtained at light satu- Measurements were ration, using an artificial light source (>800 !E-m-2-s-!): PNsat and g Light satu- sat. s Poplar, characterized by rapid growth, is rated net photosynthesis data were obtained important source of fiber products in an using a portable gas exchange system, as de- Belgium (Steenackers, 1982). Growth scribed by Ceulemans et al. (1986). Stomatal reduction due to acidic precipitation may conductances were measured with an automa- have important economic consequences. tic water vapor diffusion porometer. Poplar is known to be sensitive to Mean values of 6-12 measurements of each LPI were calculated with 95% confidence limits. gaseous air pollutants (e.g., leaf damage) Non-overlapping limits indicate significant differ- (Freer-Smith, 1984; Wang et al., 1986). In ences between the two pH treatments. this study, direct effects of acidic precipita- tion on leaf gas exchange were deter- mined for two clones. Results Materials and Methods Net photosynthesis was decreased by acid rain (pH 4.0) in cv. Beaupr6 (Fig. 1 ). Poplar cuttings (Populus sp. cv. Beaupr6 and The differences compared to the control Robusfa) were grown in a greenhouse in cv. group were highly significant for cv. Beau- plastic containers (11.2 1) and exposed to simu- pre but not for cv. Robusta. These differ- lated acidic rain of pH 4.0 or to a control solu- ences were greatest at optimal leaf age tion of pH 5.6, 3 times a week. The soil was (LPI 9 for cv. Beaupr6). A reduction (in covered with a plastic hood to avoid indirect effects of acid precipitation. PNsat) of 28.2% was recorded for cv. The interactive effects of leaf age and expo- Beaupre. to acid rain on leaf gas exchange were sure Stomatal conductances (g sat) s were studied by measuring net photosynthetic rate calculated from stomatal resistance and stomatal conductance at different leaf ages mea-
surements of upper and lower leaf sur- Acknowledgments faces (Fig. 2). For both clones and treat- ments, g shows its maximal value on sat s This study was supported by the lnstituut tot fully expanded leaves. The optimal leaf Aanmoediging van het Wetenschappelijk ages were LPI 9 for cv. Beaupr6 and LPI Onderzoek in Nijverheid en Landbouw (Brus- sels, Belgium). 12 for cv. Robusta. On the whole, acid rain caused a decrease of stomatal conduc- tance; g was reduced by 24.0% for cv. sat s Beaupr6 and by 15.4% for cv. Robusta. References Ceulemans R., Kockelbergh F. & Impens 1. (1986) A fast, low cost and low power requiring Discussion and Conclusions device for improving closed loop C0 -measur- 2 ing systems. J. Exp. Bot. 37, 1234-1244 Freer-Smith P.H. (1984) The responses of six Both clones showed a decrease for PNsat broadleaved trees during long-term exposure to as well as for g Cultivar Beaupr6 was sat. s S0 and N0 New Phytol. 97, 49-61 2 . 2 much more sensitive to acid rain treatment Steenackers V. (1982) Selectie van populieren than cv. Robusta, as well for photosynthe- voor biomassaproduktie. In: Produktie van bio- sis as for water vapor conductance. massa, notities ta.v. studiedag KI-VIV op 7 november 1982 in Bokrijk-Genk Effects of treatment were statistically signi- Wang D., Karnosky D.F. & Bormann F.H. ficant (P = 0.05) for cv. Beaupr6, but not (1986) Effects of ambient ozone on the produc- for cv. Robusta. Maximal sensitivity corre- tivity of Populus tremuloides Michx. grown sponded to maximal leaf gas exchange under field conditions. Can. J. For. Res. 16, 47- rates (optimal leaf ages). 55