|Estiaarte, Marc - CREAF BELLATERRA SPAIN|
|Penuelas, Josep - CREAF BELLATERRA SPAIN|
|Pinter Jr, Paul|
Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 1998
Publication Date: February 15, 1999
Citation: Estiaarte, M., Penuelas, J., Kimball, B.A., Hendrix, D.L., Pinter Jr, P.J., Wall, G.W., La Morte, R.L., Hunsaker, D.J. 1999. Free-air co2 enrichment of wheat: leaf flavonoid concentration throughout the growth cycle. Physiologia Plantarum 105:423-433. Interpretive Summary: The CO2 concentration of the atmosphere is increasing and is expected to double sometime during the next century. Such an increase in CO2 concentration is expected to stimulate the growth of plants although different species may respond differently or in varying degrees to the elevated CO2. The elevated CO2 may also affect the production of various biochemical compounds within the plants, and in this study, the effects on flavonoid concentrations were determined. Flavonoids are bad-tasting secondary compounds that plants make to help defend themselves from herbivores such as leaf-eating insects. We found that elevated CO2 increased the flavonoids content of wheat leaves slightly. The changes in flavonoid content were correlated with increases in carbohydrate content. Increased carbohydrates are commonly observed in high-CO2-grown plants. Information such as this is needed to help predict the consequences of the future high CO2 concentrations on agricultural productivity and on natural ecosystems.
Technical Abstract: To test the predictions that plants will have a larger flavonoid concentration in a future world with a CO2-enriched atmosphere, wheat (Triticum aestivum L. cv. Yecora Rojo) was grown in a field experiment using (FACE (free-air CO2 enrichment) technology under two levels of atmospheric CO2 concentration: ambient (370 umol mol-1) and enriched (550 umol mol-1). We also studied the effects of CO2 on the concentration of total non-structural carbohydrates (TNC) and nitrogen (N), two parameters hypothesized to be linked to flavonoid metabolism. Throughout the growth cycle the concentration of isoorientin, the most abundant flavonoid, decreased by 62% (from an average of 12.5 mg g-1 on day of year (DOY) 41 to an average of 4.8 mg g-1 on DOY 123), whereas the concentration of tricin, another characteristic flavone, increased by two orders of magnitude (from an average of 0.007 mg g-1 of isoorientin equivalents on DOY 41 to an average of 0.6 mg g-1 of isoorientin equivalents on DOY 123). CO2-enriched plants had higher flavonoid concentrations (14% more isoorientin, an average of 7.0 mg g-1 for ambient CO2 vs an average of 8.0 mg g-1 for enriched CO2), higher TNC concentrations, and lower N concentrations in upper canopy leaves throughout the growth cycle. These results are in accordance with the hypotheses that higher carbon availability promoted by Co2-enrichment provides carbon that can be invested in carbon-based secondary compounds such as flavonoids. The rise in atmospheric CO2 may thus indirectly affect wheat-pest relations, alter the pathogen predisposition, and improve the UV-B protection by changing flavonoid concentrations.