The effect of subambient to elevated atmospheric CO 2 concentration on vascular function in Helianthus annuus : implications for plant response to climate change

• Published in: The New phytologist Vol. 199; no. 4; pp. 956 - 965
• Main Authors: Rico, Christopher, Pittermann, Jarmila, Polley, H. Wayne, Aspinwall, Michael J., Fay, Phillip A.
• Format: Journal Article
• Language: English
• Published: 01.09.2013
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.12339

Summary Plant gas exchange is regulated by stomata, which coordinate leaf‐level water loss with xylem transport. Stomatal opening responds to internal concentrations of CO 2 in the leaf, but changing CO 2 can also lead to changes in stomatal density that influence transpiration. Given that stomatal conductance increases under subambient concentrations of CO 2 and, conversely, that plants lose less water at elevated concentrations, can downstream effects of atmospheric CO 2 be observed in xylem tissue? We approached this problem by evaluating leaf stomatal density, xylem transport, xylem anatomy and resistance to cavitation in Helianthus annuus plants grown under three CO 2 regimes ranging from pre‐industrial to elevated concentrations. Xylem transport, conduit size and stomatal density all increased at 290 ppm relative to ambient and elevated CO 2 concentrations. The shoots of the 290‐ppm‐grown plants were most vulnerable to cavitation, whereas xylem cavitation resistance did not differ in 390‐ and 480‐ppm‐grown plants. Our data indicate that, even as an indirect driver of water loss, CO 2 can affect xylem structure and water transport by coupling stomatal and xylem hydraulic functions during plant development. This plastic response has implications for plant water use under variable concentrations of CO 2 , as well as the evolution of efficient xylem transport.