Effects of CO2-fertilization on Evapotranspiration
Concentrations of greenhouse gases are increasing rapidly. It is most likely that the present CO2 concentrations will be doubled by about the middle of the next century. An important question to answer, when considering the role of water and the hydrological cycle in global change, is to what extent the stomata of plants, whole plants or entire plant communities adapt to changing CO2 concentrations. Plant response could alter the temporal or spatial distribution of evaporation from terrestrial systems.
Changes in the ambient CO2 concentrations primarily affect the net photosynthesis of C3-plants, the majority of the plant species. Higher ambient concentrations also increase the concentration gradient which is the driving force for diffusion of CO2 into the stomatal cavities. This larger gradient and the concurrent higher diffusion rate are counteracted to some extent by a partial closure of the stomata, thus reducing the transpirational loss of water from the leaves. The instantaneous transpiration efficiency, the ratio between assimilation and transpiration rates, thus increases both by enhanced carbon assimilation and simultaneous reduced transpiration.
An enhanced carbon assimilation rate induces a stimulated growth. For annual crops increased assimilation causes a faster canopy development in spring thus reducing soil evaporation and increasing plant transpiration. However, the carbon allocation in the plant not only depends on the growth stage but also on stress factors that limit growth. Plants with limited water or nutrient availability show increased root:shoot ratios when grown at higher CO2 levels. Plants tend to adjust their carbon allocation so that limitation of growth by different resources is equalized as much as possible.
Long term changes of natural ecosystems are difficult to predict. It is the combination of stress factors, and their spatial and temporal variability, on the one hand and differences of sensitivity among plant species to these factors on the other hand that determine the outcome of competition and the resulting biological diversity.
KeywordsMesophyll Cell Carbon Assimilation Stomatal Aperture Carbon Allocation Stomatal Resistance
Unable to display preview. Download preview PDF.
- Ammerlaan F.H.M., de Visser A.J.C. (1993) Effects of CO2 enrichment on photosynthesis and carbohydrate utilisation: consequences for regrowth of Lolium perenne. In: S.C. vander Geijn, J. Goudriaan, F. Berendse (eds), Climate change, crops and terrestrial ecosystems: 1–22, AB-DLO, Wageningen, the NetherlandsGoogle Scholar
- Arkley R.J. (1963) relationships between plant growth and transpiration. Hilgardia 34: 559–584.Google Scholar
- Ball J.T., Woodrow I.E., Berry J.A. (1987) A model predicting stomatal conductance and its contribution to the control of photosynthesis under different environmental conditions. Prog. Photosynth. Res. 5: 221–224.Google Scholar
- Bloom A.J., Chaplin III F.S., Mooney H.A. (1985) Resource limitation in plants - an economic analogy. Ann. Rev. Ecol. Syst. 16: 363–392.Google Scholar
- Butler J.N. (1982) Carbon dioxide equilibria and their applications. Addison-Wesley Publ. Corp.Google Scholar
- Clayton R.K. (1981) Photosynthesis. Cambridge: Cambridge University Press.Google Scholar
- de Wit C.T. (1958) Transpiration and crop yield, Versl. Landbouwk. Onderz. 64.6.Google Scholar
- Evens L., Peterson R., Lee H.S.J., Jarvis P.G. (1993) Effects of elevated CO2 on birch, Vegetatio, 104/105: 452–453Google Scholar
- Gibbs M., Latzko E. (eds.) (1979) Photosysnthesis, vol.2, Photosynthetic carbon metabolism and related processes. Berlin: Springer-Verlag.Google Scholar
- Goudriaan J., de Ruiter H.E. (1983) Plant growth in response to CO2 enrichment, at two levels of nitrogen and phosphorus supply. 1. Dry matter, leaf area and development. Neth. J. Agric. Sci. 31:157–169.Google Scholar
- Goudriaan J., Unsworth M.H. (1990) Implications of increasing carbon dioxide and climatic change for agricultural productivity and water resources. ASA Spec. Publ. 53: 111–130.Google Scholar
- Hatch M.D., Boardman N.K. (eds.), (1981) The biochemistry of plants, vol.3, Photosynthesis. New York: Academic Press.Google Scholar
- Jacobs C.M.J. (1994) Direct impacts of atmospheric CO2 enrichment on regional transpiration. PhD-thesis, Wageningen Agric. Univ., the Netherlands, 179 pp.Google Scholar
- Tanner C.B., Sinclair T.R. (1983) Efficient water use in crop production: Research or re-search? in: H.M. Taylor, W.R. Jordan and T.R. Sinclair (eds.), Limitations to efficient water use in crop production. Am. Soc. Agron.Google Scholar
- Trebst A., Avron M. (eds.), (1977) Photosynthesis, vol.1, Photosynthetic electron transport and photophosphorylation, Berlin: Springer-Verlag.Google Scholar