Home

Editors

Contents

Contribute

Subscribe

Contact

Leaf photosynthetic characteristics of beech (Fagus sylvatica) saplings during three years of exposure to elevated CO₂ concentration

Rodolphe Liozon (1), Franz-Werner Badeck (2), Bernard Genty (1), Sylvie Meyer (1) and Bernard Saugier (1)

1. Laboratoire d'Ecophysiologie Végétale, UPRESA 8099, Université de Paris Sud, Bât. 362, 91405 Orsay Cedex, France / 2. Potsdam Institute for Climate Impact Research (PIK), PF 60 12 03, 14412 Potsdam, Germany / Received March 3, 1999

Summary

Beech (Fagus sylvatica L.) seedlings were cultivated from seeds sown in pots or directly in the ground in outdoor chambers that were transparent to solar radiation, and provided either ambient air or CO₂-enriched air (ambient + 350 μmol mol^–1). The rooting volume was high in all experiments. In the short-term experiment, potted plants were assigned to a factorial CO₂ × nutrient treatment (optimal nutrient supply and severe nutrient shortage) for 1 year. In the long-term experiment, plants were grown directly in the ground and received an optimal supply of water and nutrients in both CO₂ treatments for 3 years. 

Nutrient stress caused carboxylation capacity (V_m) to decrease in the potted seedlings exposed to CO₂-enriched air during their first growing season. In the long-term experiment with optimal nutrient supply, CO₂-enriched air did not affect V_m, but caused an upward acclimation of maximum electron transport rate (J_m). Consequently, there was a 14% increase in the J_m/V_m ratio, indicating nitrogen reallocation to maintain an equilibrium between RuBP consumption and RuBP regeneration. Both V_m and J_m decreased during the growing season in both CO₂ treatments. Although upward acclimation of J_m was no longer apparent at the end of the third growing season, plants in CO₂-enriched air maintained a higher J_m/V_m ratio than plants in ambient air, indicating that photosynthetic acclimation always occurred. Second flush leaves appeared during each growing season. When expressed on the basis of foliar nitrogen concentration, their photosynthetic characteristics (V_m and J_m) were enhanced compared with other leaves. Because the number of second flush leaves was also increased in the elevated CO₂ treatment, this response should be taken into account when modeling the effects of elevated CO₂ concentration on canopy photosynthesis. Stomatal conductance decreased in response to atmospheric CO₂ enrichment; however, the stomatal response to irradiance followed a single relationship based on two stomatal conductance models.

Keywords: carbon dioxide, CO₂ acclimation, leaf photosynthesis, nutrient supply, stomatal conductance.

---

ISSN 0829-318X Copyright © 2002–2008 Heron Publishing