Summary

The impact of elevated CO2 (1000µmol/mol) was assessed on the common weed, Arabidopsis tha-liana (Landsberg erecta), which is used as a model plant system. Elevated CO2 stimulated relative growth rate (RGR) and leaf area gain of Arabidopsis beginning from the cotyledon stage and contin-uing through the juvenile stage. This early advantage in growth enabled the plants grown in elevated CO2 to gain more DW despite similar RGRs throughout the latter stages of development. The greater accumulation of DW in leaves grown in elevated CO2 resulted in a lower specific leaf area (SLA). However, the amount of cell wall investment per unit of leaf area, specific “wall ” area (SWA), was similar indicating that elevated CO2 did not affect the distribution of cell carbon to the cell wall of leaves beyond that needed for cell and leaf expansion. Furthermore, cell wall composition changed with time due to developmental changes and was not affected by elevated CO2. Associated with the increase in RGR by elevated CO2 was a concomitant increase in the activity of UDP-Glc dehydro-genase (E.C. 1.1.1.22), a key enzyme in the nucleotide–sugar interconversion pathway necessary for biosynthesis of many cell-wall polysaccharides. Key words: Arabidopsis thaliana – cell wall – elevated carbon dioxide – growth – UDP-Glc dehydro-genas