This thesis employs two techniques to investigate the influence of carbon dioxide concentration on carbon assimilation in tropical tree species. To investigate the response of tropical tree species to elevated CO<SUB>2</SUB> concentration, seedlings of <I>Cedrela odorata</I> L. (Meliaceae) were grown in open-top chambers and exposed to atmospheric CO<SUB>2</SUB> at either ambient or twice ambient concentrations. Nutrient supply rate was also altered to investigate its interaction with elevated CO<SUB>2</SUB> concentration. This experiment was repeated on different seedlings over two years, 1995 and 1996, with <I>C. odorata</I> showing an acclimation response to elevated CO<SUB>2</SUB> concentration in the second year of the experiment but not in the first. Plants grown in elevated CO<SUB>2</SUB> concentration were larger than those grown in ambient CO<SUB>2</SUB> concentration in 1995 only with a high rate of nutrient supply. It is hypothesised that high vapour pressure deficits restricted stomatal conductance and consequent photosynthesis in both years but that this effect was particularly pronounced in 1996 when combined with a nutrient regime of excessively high concentration for the rate of growth. These effects are hypothesised to have triggered acclimation, or a reduction in CO<SUB>2</SUB> fixation capacity, as indicated by changes in derived values for the enzyme kinetic parameters of the carboxylation enzyme, ribulose 1,5 bisphosphate carboxylase-oxygenase (Rubisco). A biochemical model of photosynthesis was used to assess photosynthetic acclimation to elevated CO<SUB>2</SUB> concentration. The derived parameters for maximum rate of electron transport (<I>J<SUB>max</SUB></I>) and maximum velocity of the Rubisco enzyme (<I>V<SUB>max</SUB></I>) were compared between treatment CO<SUB>2</SUB> concentrations and both were significantly lower (<I>p</I> < 0.05) in plants that had been grown in elevated CO<SUB>2</SUB> concentration in 1996. Whole-plant gas exchange was monitored in 1996, where a decrease in net CO<SUB>2</SUB> uptake of plants grown in elevated CO<SUB>2</SUB> concentration was observed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:642644 |
| Date | January 1998 |
| Creators | Carswell, F. E. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13328 |
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