Interactions of SO2 with other environmental stresses in influencing leaf gas exchange

• Published in: Oecologia 1990-10, Vol.84 (4), p.500-505
• Main Authors: Atkinson, C.J, Winner, W.E
• Format: Article
• Language: English
• Subjects: Air pollutants; Animal, plant and microbial ecology; Applied ecology; Atmospherics; Biological and medical sciences; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Environmental pollution; Fumigation; Fundamental and applied biological sciences. Psychology; gas exchange; Heteromeles salicifolia; Leaves; photosynthesis; Plants; Relative humidity; Scrophulariaceae; Stomatal conductance; sulfur dioxide; Sulphur dioxide; temperature; Water vapor
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/BF00328166

Leaves of two field growing co-occuring pe-rennial 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 μmol m-3, 0.1 μl 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 ΔW 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.