| Popis: |
The International Panel on Climate Change (IPCC) predicted, from current trends in emissions and uptake, that the atmospheric CO2 concentration (Ca) would rise from its 1990 level of 354 μmol mol-1 to ca. 530 μml-1 mol-1 by 2050 and to over 700 μmol mol-1 by the end of the next century; i.e. a doubling of the present concentrations (Watson et al., 1990). This increase in the concentration of CO2 and other heteroatomic gas molecules in the troposphere is expected to lead to an increase in mean global temperatures of ca. 3°C by 2050 and ca. 4°C by 2100 (Watson et al., 1990). Tropospheric O3 concentrations in western Europe are expected to rise in parallel with CO2 concentrations from ca. 50 nmol mol-1 in 1990 at ca. 0.5% p.a. (Dizengremel, 1992) and are likely to depress concentrations of RubisCO in leaves which develop in these atmospheres (Pell, 1992). Rising tropospheric CO2 and O3 concentrations will modify the response of photosynthesis to a wide range of environmental variables, in particular temperature (Long, 1991). Any consideration of the effects of rising CO2 concentrations on photosynthetic production must therefore incorporate the interactive effects of rising temperature and rising tropospheric O3 concentration (Farage et al., 1991; Long, 1991; Long & Hutchin, 1991) |
