Báo cáo lâm nghiệp: "delayed effect of ozone fumigation on photosynthesis of Norway spruce"

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Nội dung Text: Báo cáo lâm nghiệp: "delayed effect of ozone fumigation on photosynthesis of Norway spruce"

A delayed effect of ozone fumigation on photosynthesis of Norway spruce D. Eamus J.D. Barnes L. Mortensen 2 1 3 H. Ro-Poulsen 4 A.W. Davis n 2 2avison 1Institute of Terrestrial Ecology, Bush Estate, Penicuik, Midlothian EM?6 OOB, U.K., Department 2 of Biology, Ridley Building, The University, Newcastle upon Tyne, U.K., National 3 Agency of Environmental Research, Institute of Air Pollution, Frederiksborgvej 399, D-4000, Roskilde, Denmark, and 1nstitute 4 of Plant Ecology, University of Copenhagen, 0 Farimagsyade, 2D Dli353. Copenhagen, Denmark peratures and light intensity are sufficiently Introduction high. Frost and winter dessication are therefore temporally separated from the Much of the research investigating the periods of high ozone concentrations. effects of gaseous pollutants upon plants Consequently, if ozone is to influence has been concerned with dose-response plant sensitivity to frost, it must exert a relationships, particularly during the period long-lasting effect. This paper briefly of fumigation or in between the periods of reports the results of an investigation into fumigation, in the summer. However, there the long-lastinc effects of ozone fumiga- l is increasing evidence that these pollu- tion upon photosynthesis of Norway tants increase plant susceptibility to winter spruce. Measurements were conducted in injury (Barnes and Davison, 1988; Brown the field 6-7 mo after the cessation of 2 yr ef al., 1987). This is especially problematic summer fumigation with ozone. for conifers, since they maintain needles and some metabolic activity throughout the winter. Indeed, there is increasing evi- dence that the forest decline documented Materials and Methods for northeastern U.S.A. and Europe results from the interaction of various abiotic and biotic factors including air pol- Four yr old trees of Norway seedl-propagated lutants, frost and winter dessication spruce (Picea alries (L.) Karst) were exposed, (Brown et aL, 1987; Barnes and Davison, in duplicate open top chambers at Riso National Laboratory, 30 krn west of Copenhagen, Den- 1988). mark, to either charcoal-filtered air or ambient Anthropogenic ozone production primar- air plus 50 ppb ozone, from July to October the when tem- ily during 1986 and May to October, 1987. occurs summer
On November 25th, 1987 (42 d after the ces- sation of ozone fumigation), branches bearing 3 needle yr age classes were used for fluores- cence analysis. A portable fluorometer (Richard Branker Research) attached to an oscilloscope with output to a digital plotter was used (Barnes and Davison, 1988). F was readily determined o due to the storage and display capabilities of the Gould 1425 digital storage oscilloscope, allowing millisecond resolution of the fluores- cence curves. Fluorescence of wavelength > 710 nm (PS[I fluorescence) was measured. The Branker instrument provides illumination of approximately 4 ¡ae F (non-variable . 1 s 2 m- ’o fluorescence), F (variable fluorescence) and F v r (rate of rise of variable fluorescence) were determined as described elsewhere (Barnes and Davison, 1988). On May 8th, 1988 (207 d after the cessation of fumigation), rates of pho- tosynthesis and transpiration were measured in the field using a portable ADC infrared gas ana- lyzer and Parkinson leaf chamber. Current and previous yr needles were used. Twelve repli- cate branches per treatment were measured. Further details are given elsewhere (Eamus et al., 1989) Results ozone-filtered trees. Similarly, ozone fumi- TableI shows that for both current and gated trees fixed 29% (current) and 50% previous yr needles, the mean rate of (previous) more C0 per hour than char- 2 assimilation over the day was significantly coal-filtered trees. From Figs. 1 and 2, it (P
Table II shows that there and previous yr needles (Fig. 1), and 2) signifi- was no both a greater light saturated rate of assi- cant effect of the treatments upon F for , o any of the 3 yr classes of needles. How- milation and a higher apparent quantum yield than the charcoal-filtered trees (Fig. ever, the yield of variable fluorescence 2). The r! values for the apparent quantum (F was significantly reduced in all yr ) v yield regressions of the light response classes, by ozone fumigation. The rate of rise of variable fluorescence (F was data (Fig. 2) and the temperature respon- ) r significantly decreased in current yr se of assimilation (Fig. 1) varied between 0.8 and 0.97, indicating a satisfactory fit of needles only. There was no effect on C+11 or C+2 yr needles. the lines to the data sets.
and previous yr needles (Table I). This Discussion and Conclusion result is in contradiction with the data of large numbers of papers reporting that ozone fumigation causes decreased rates fumigation resulted in significantly Ozone of assimilation (A). However, examples of mean daily rates of assimilation enhanced ozone fumigation not affecting rates of A in comparison to control plants, for current
tosynthetic processes (principally electron (Chappelka and Chevone, 1988; Taylor et transport) which was not expressed as al., 1986) have been reported. The majori- visible symptoms. Such latent damage ty of these papers have been concerned with measurements of A has been associated with increased frost during the sum- coincidental with the time of sensitivity (Barnes and Davison, 1988). period mer ozone fumigation. The data presented in These changes in fluorescence parame- ters were observed 42 d after cessation of this paper show that ozone increased A in the spring prior to budburst following a ozone fumigation, indicating that these summer of ozone fumigation. Ozone trees were more sensitive to early frost events as well as late frost events. decreases frost hardiness of Norway and Sitka spruce (Barnes and Davison, 1988; Lucas et al., 1988) particularly at the start and end of the winter period (i.e., during hardening and dehardening). It is suggest- References ed from the data of this study, that trees exposed to ozone during the summer Barnes J.D. & Davison A.W. (1988) The influ- were less hardy in May the following yr ence of ozone on the winter hardiness of Nor- and thus were more active than control way spruce. Neuv Phytol. 108, 159-166 plants. From this it may be predicted that Brown K.A., Roberts T.M. & Blank L.W. (1987) ozone-fumigated trees would have a Interaction between ozone and cold sensitivity and light response higher temperature in Norway spruce: a factor contributing to the forest decline in central Europe. New Phytol. for A than control plants which were curve 105, 149-155 hardier and less metabolically active. This Chappelka A.H., Chevone B.I. & Seiler J.R. indeed was observed. Quantum efficiency, (1988) Growth and physiological responses of the rate of light-saturated A and the tem- yellow poplar seedlings exposed to ozone and perature response of A was greater in simulated acidic rain. Environ. Pollut. 49, 1-18 8 ozone-fumigated plants than controls Eamus D. & Fowler D. (1989) Photosynthetic (Figs. 1 and 2, Table I). It is concluded that and stomatal conductance responses of red ozone fumigation exerts a long-term effect spruce seedlings to acid mist. Plant Cell Envi- ron. in press upon Norway spruce via its influence upon the processes of hardening and sub- Eamus D., Barnes J.D., Mortensen L., Ro-Poul- sen H. & Davison A.W. (1989) Persistent effects sequent dehardening. This makes the of summer ozone fumigation on C0 assimila- 2 trees more frost sensitive, but also allows tion and stom;atal conductance in Norway the ozone fumigated trees to take better spruce. Environ. Pollut in press advantage of warm, sunny days early in Lucas P.W., Cottam D.A., Sheppard L.J. & the season. Francis B.J. (1988) Growth responses and delayed winter hardening in Sitka spruce follow- Table II shows that ozone fumigation ing summer exposure to ozone. New Phytol. significantly reduced the yield of variable 108, 495-504 fluorescence (F for all yr classes, and ) v Taylor G.E., Norby R.J., McLaughlin S.B., John- also the rate of rise (F of induced fluores- ) r son A.H. & Turner R.S. (1986) Carbon dioxide cence in the current yr needles. Such assimilation and growth of red spruce seedlings declines indicate that previous exposure to in response to ozone and precipitation chemis- 0 caused long-term damage to the pho- try and soil type. Oecologia (Berlin) 70, 163-171 3