© 1996 Heron Publishing—Victoria, Canada
Effects of elevated CO2 concentration on leaf characteristics and photosynthetic capacity of beech (Fagus sylvatica) during the growing season
Daniel Epron (1, 2), Rodolphe Liozon (1) and Marianne Mousseau (1)
1. Laboratoire d'Ecologie Végétale, CNRS URA 1492, Université Paris Sud, Batîment 362, 91405 Orsay cedex, France / 2. Laboratoire de Sciences Végétales, Institut des Sciences et des Techniques de l'Environnement, Pôle Universitaire, BP 427,
25211 Montbéliard cedex, France / Received April 13, 1995
Summary
Two-year-old beech (Fagus sylvatica L.) saplings were planted directly in the ground at high density (100 per m2), in an experimental design that realistically mimicked field conditions, and grown for two years in air containing CO2 at either ambient or an elevated (ambient + 350 ppm) concentration. Plant dry mass and leaf area were increased by a two-year
exposure to elevated CO2. The saplings produced physiologically distinct types of sun leaves associated with the first and second growth flushes.
Leaves of the second flush had a higher leaf mass per unit area and less chlorophyll per unit area, per unit dry mass and
per unit nitrogen than leaves of the first flush. Chlorophyll content expressed per unit nitrogen decreased over time in plants
grown in elevated CO2, which suggests that, in elevated CO2, less nitrogen was invested in machinery of the photosynthetic light reactions. In early summer, the photosynthetic capacity
measured at saturating irradiance and CO2 was slightly but not significantly higher in saplings grown in elevated CO2 than in saplings grown in ambient CO2. However, a decrease in photosynthetic capacity was observed after July in leaves of saplings grown in CO2-enriched air. The results demonstrate that photosynthetic acclimation to elevated CO2 can occur in field-grown saplings in late summer, at the time of growth cessation.
Keywords:
acclimation, leaf, photosynthesis.
