Acclimatory responses of stomatal conductance and photosynthesis to elevated CO 2 and temperature in wheat crops grown at varying levels of N supply in a Mediterranean environment

Abstract

The short and long-term responses of flag leaf stomatal conductance ( g s) and rate of photosynthesis (An) to elevated CO 2 (757 μmol mol −1), 4 °C warmer temperatures and N supply were investigated in spring wheat ( Triticum aestivum L. cv. Alcalá) crops grown in two seasons in field conditions under temperature gradient tunnels in a Mediterranean environment. Plants grown at elevated CO 2 had lower g s and An measured at 700 μmol mol −1 CO 2 than ambient CO 2-grown plants, indicating acclimatory responses to elevated CO 2. N supply, which was lower in 2003 than 2002, reduced this acclimation in both years. Warmer temperatures at high nitrogen supply also decreased An acclimation. Acclimatory responses of An and g s were highly correlated. The analysis of the g s–An relationship indicated that both parameters are probably linked and respond in parallel to elevated CO 2 at ambient temperatures, but non-parallel responses were observed at above-ambient temperatures.