THE RESPONSE OF FOLIAR CARBOHYDRATES TO ELEVATED CARBON DIOXIDE CONCENTRATION

Authors: ROGERS, ALISTAIR - BROOKHAVEN NATIONAL LAB; Ainsworth, Elizabeth - Lisa

Submitted to: Springer Verlag
Publication Type: Book / Chapter
Publication Acceptance Date: 4/28/2005
Publication Date: 6/1/2006
Citation: Rogers, A., Ainsworth, E.A. 2006. The response of foliar carbohydrates to elevated carbon dioxide concentration. In: Springer. Managed Ecosystems and CO2, Nosberger, J. Long, S.P., Stitt, G.R., Hendrey, G.R. Blum H., editors. Heidelberg, Germany: Springer. p.296-310.

Interpretive Summary: One of the most common responses of plants to elevated atmospheric carbon dioxide concentration is an increase in leaf sugar concentration. We reviewed the response of different plant species to growth at elevated atmospheric carbon dioxide concentration and found that plants with limited “sink” capacity, or those with smaller energy demands, showed large accumulation of carbohydrates. Elevated atmospheric carbon dioxide experiments in the field confirmed results from growth chamber and greenhouse studies; sink capacity is an important factor determining the extent and timing of increase in leaf carbohydrate concentration. In order to more fully understand the effect of elevated carbon dioxide on leaf sugars, we also need to consider leaf age or developmental stage and nitrogen metabolism.

Technical Abstract: Accumulation of foliar carbohydrates is one of the most pronounced and universal changes observed in the leaves of C3 plants grown at elevated CO2 concentration ([CO2]). Carbohydrates are both the product of photosynthetic cells, and the substrate for sink metabolism. However, carbohydrates are not just substrates, and the role of carbohydrates in regulation of the expression of many plant genes, and the activity of many key enzymes, is well established. As Free Air CO2 Enrichment (FACE) technology was emerging, understanding of the link between carbohydrates and plant responses to growth at elevated [CO2] (e [CO2]) was increasing. However, it remained unclear whether the hypotheses that were being refined in model systems would hold up when tested in open-air field experiments. More than a decade of FACE experiments have provided the answer. Despite predictions that foliar carbohydrates would not accumulate in the leaves of plants grown at e [CO2] in the field where roots are free to develop and explore the soil for nutrients, plants grown in the field using FACE technology still accumulated carbohydrate. Even N-fixing species with large sink capacities exhibited exacerbated carbohydrate accumulation at e [CO2] and perennial ryegrass showed evidence of a severe sink limitation. FACE experiments have confirmed the importance of sink capacity in determining the timing and extent of foliar carbohydrate accumulation, and have provided a valuable field test for key indicators of insufficient sink capacity.