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  • 1
    Electronic Resource
    Electronic Resource
    Interactions of SO2 with other environmental stresses in influencing leaf gas exchange (1990)
    Springer
    Oecologia 84 (1990), S. 500-505 
    Details
    ISSN: 1432-1939
    Keywords: Air pollution ; Diplacus aurantiacus (Curtis) Jeps ; Heteromeles arbutifolia (Ait.) Roem ; Environmental stresses ; Gas exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328166
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  • 2
    Electronic Resource
    Electronic Resource
    Gas exchange and SO2 fumigation studies with irrigated and unirrigated field grown Diplacus aurantiacus and Heteromeles arbutifolia (1988)
    Springer
    Oecologia 75 (1988), S. 386-393 
    Details
    ISSN: 1432-1939
    Keywords: Diplacus aurantiacus (Curtis) Jeps. ; Heteromeles arbutifolia (Ait.) Roem. ; Gas exchange ; Irrigation ; Sulphur dioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Experiments were performed on an evergreen (Heteromeles arbutifolia) and a drought deciduous shrub (Diplacus aurantiacus) to determine, 1) whether approaches for evaluating SO2 absorption by leaves in laboratory studies could be extended to field studies, 2) the effects of irrigation on metabolism and SO2 responses of the study species during a season when water was limiting, 3) to interpret SO2 responses on the basis of SO2 flux rates. Laboratory-developed approaches for evaluating SO2 absorption by leaves were found to be suitable for use with field plants, despite field plants having lower gas exchange rates. Supplementing water during times of deficit did not override all the biological and environmental factors that limited photosynthesis (A). Irrigation increased leaf longevity of D. aurantiacus, and stomatal conductance to water vapour (g); g was also shown to increase with H. arbutifolia on irrigation. Irrigation profoundly influenced plant response to SO2. Unwatered D. aurantiacus had only a small g and therefore a reduced capacity to absorb SO2 and respond to SO2; which resulted in apparent SO2 avoidance. Water availability and SO2 both affect g and therefore, SO2 flux rates into the mesophyll. Different ambient SO2 concentrations of 8.3 and 26.2 μmol m-3 (0.2 and 0.6 ppm) were both found to result in similar SO2 flux rates into the leaf, due to variations in g in response to water availability. Changes in g did not always result in changes in A, implying that carbon fixation may be little affected by some SO2 exposures, although still potentially affecting such processes as maintenance of leaf water potential, transpirational cooling and nutrient uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376941
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  • 3
    Electronic Resource
    Electronic Resource
    Putative anaerobic activity in aerated composts (1996)
    Springer
    Journal of industrial microbiology and biotechnology 16 (1996), S. 182-188 
    Details
    ISSN: 1476-5535
    Keywords: enzymes ; anaerobes ; municipal solid waste ; pulp and paper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract It has been suggested that anaerobic microenvironments develop in aerobic composts, regardless of the aeration system used, and that anaerobic activity is responsible for odor generation and nitrogen losses. This study was designed to measure levels of microorganisms capable of anaerobic growth in two aerated composts: municipal solid waste, a relatively nutrient-rich compost, and pulp and paper-mill solid waste, which is relatively nutrient-poor. Anaerobic microorganisms were isolated from both composts at mesophilic and thermophilic temperatures. The majority of the anaerobic mesophiles were facultative anaerobes, whereas facultative, anaerobic thermophiles varied from 0 to 100%. Serially-diluted samples were spot-plated onto various media to preserve microbial consortia. Levels of aerobic and anaerobic exoenzyme production on spot-plates were similar on cell-wall, starch, and casein media. Although microbial levels on spread plates indicate that aerobes are present in much higher numbers than anaerobes (in 47 of 56 subsamples, 90% of the population were aerobes), microbial growth levels and exoenzyme production on spot-plates indicate that anaerobes may be responsible for a large portion (greater than or equal to 72%) of the metabolic activity in anaerobic microenvironments of aerobic composts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01570002
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    Paper (German National Licenses)
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