Limitations of Photosynthesis in Lolium perenne after Chilling

Abstract

Photosynthesis was reduced by 85% to 90% in perennial ryegrass (Lolium perenne L. cv. Derby) following a one-day chilling exposure at 8C day (450 μmol·s -1 ·m -2 PPF) and 5C night. Seven days of recovery at 22/17C day/night were required for full recovery of photosynthesis. More than 75% of the limitation in photosynthesis following chilling was due to non-stomatal factors, and reduced initial slopes of CO 2 assimilation vs. intercellular CO, indicate that photosynthetic capacity was reduced for 5 days following chilling. Carbon dioxide assimilation at saturating intercellular CO 2 (>500 μmol·mol -l ) was also reduced by chilling, indicating again that stomatal limitations were a minor contributor to the photosynthetic reduction observed under ambient CO 2 .