Interactions of SO2 with other environmental stresses in influencing leaf gas exchange |
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Authors: | C J Atkinson W E Winner |
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Institution: | (1) Division of Biological Sciences, Institute of Environmental and Biological Sciences, Lancaster University, LA1 4YQ Lancaster, UK;(2) Department of General Science, Oregon State University, 97331 Corvallis, OR, USA |
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Abstract: | Summary Leaves of two field growing co-occuring perennial shrubs (drought-deciduous Diplacus aurantiacus and the evergreen Heteromeles arbutifolia) from the Californian chaparral were exposed to small doses of SO2. During this exposure the leaf environment was manipulated to determine how the presence of SO2 alters the response of gas exchange to other environmental stresses. The data show that no direct changes in stomatal conductance (g) or net assimilation rate (A) could be attributed to short-term (7 h) SO2 (4.2 mol m-3, 0.1 l l-1) exposure. D. aurantiacus leaves possessed features which demonstrate that they were sensitive to changes in environment e.g. light flux and atmospheric relative humidity. The interspecific differences in stomatal sensitivity to water vapour were extremely important, as relative humidity is a major factor influencing carbon fixation and the rate of pollutant absorption. Conditions of high relative humidity and high xylem water potentials are suggested to pre-dispose leaves of D. aurantiacus to greater pollutant doses than the more stomatally-conservative evergreen, H. arbutifolia. In the presence of SO2 there was some indication of increased g for both D. aurantiacus and H. arbutifolia as W became smaller. This SO2-effect was only obvious as increasing atmospheric humidity induced further stomatal opening. The important consequences of an SO2 enhanced g, were a reduction in WUE, which may cause earlier leaf abscission and a concomitant decline in productivity.Abbreviations
A
net photosynthesis
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A
max
maximum rate light saturated photosynthesis
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E
transpiration; g stomatal conductance to water vapour
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QY
apparent incident quantum yield
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W
water vapour mole fraction difference between the leaf and the air
- SO2
Sulphur dioxide
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WUE
water use efficiency (mol CO2 fixed per mol H2O-1 transpired) |
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Keywords: | Air pollution Diplacus aurantiacus (Curtis) Jeps Heteromeles arbutifolia (Ait ) Roem Environmental stresses Gas exchange |
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