effect of subambient to elevated atmospheric CO2 concentration on vascular function in Helianthus annuus: Implications for plant response to climate change

• Published in: New phytologist Vol. 199; pp. 956 - 965
• Main Authors: Rico, Christopher W, Pittermann, Jarmila, Polley, H. Wayne, Aspinwall, Michael J, Fay, Philip A
• Format: Publication
• Language: English
• Published: 2013
• Subjects: carbon dioxide; carbon dioxide enrichment; climate change; evolution; gas exchange; Helianthus annuus; leaves; plant development; plant response; shoots; stomata; stomatal conductance; stomatal movement; translocation (plant physiology); xylem

Plant gas-exchange is regulated by stomata, which co-ordinate leaf-level water loss with xylem transport. Stomatal opening responds to internal levels of CO2 in the leaf but changing CO2 can also lead to changes in stomatal density that influence transpiration. Given that stomatal conductance increases under sub-ambient levels of CO2 and conversely, that plants lose less water at elevated levels, can downstream effects of atmospheric CO2 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 CO2 regimes ranging from pre-industrial to elevated levels. Xylem transport, conduit size and stomatal density all increased at 260 ppm relative to ‘ambient’ and elevated CO2 levels. The shoots of the 260-ppm grown plants were most vulnerable to cavitation whereas xylem cavitation resistance did not differ in 370 and 480-ppm grown plants. Our data indicate that even as an indirect driver of water loss, CO2 can affect xylem structure and water transport by coupling stomatal and xylem hydraulic function during plant development. This plastic response has implications for plant water-use under variable levels of CO2, as well as the evolution of efficient xylem transport.