© 2004 Heron Publishing—Victoria, Canada
Genotypic variation in drought response of silver birch (Betula pendula): leaf water status and carbon gain
Stella Aspelmeier (1, 2, 3) and Christoph Leuschner (4)
1. 32 Craighall Avenue, Manchester M19 2BR, United Kingdom / 2. Uferweg 2, 37077 Gottingen, Germany / 3. Corresponding author (stella@aspelmeier.de) / 4. Plant Ecology, Albrecht-von-Haller-Institute for Plant Sciences, University of Göttingen, Untere Karspüle 2, 37073 Göttingen,
Germany / Received March 24, 2003; accepted September 28, 2003; published online March 1, 2004
Summary
To assess genotypic variation in drought response of silver birch (Betula pendula Roth), we studied the plasticity of 16 physiological traits in response to a 12–14-week summer drought imposed on four clones
in two consecutive years. In a common garden experiment, 1-year-old clonal trees from regions with low (550 mm year–1) to high rainfall (1270 mm year–1) were grown in 45-l pots, and leaf gas exchange parameters, leaf water potentials, leaf osmotic potentials and leaf carbon
isotope signatures were repeatedly measured. There were no clonal differences in leaf water potential, but stomatal conductance
(gs), net photosynthesis at ambient carbon dioxide concentration, photosynthetic water-use efficiency, leaf carbon isotope composition
(δ13C) and leaf osmotic potentials at saturation (Π0) and at incipient plasmolysis (Πp) were markedly influenced by genotype, especially gs and osmotic adjustment. Genotypes of low-rainfall origin displayed larger osmotic adjustment than genotypes of high-rainfall
origin, although their Π0 and Πp values were similar or higher with ample water supply. Genotypes of low-rainfall origin had higher gs than genotypes of high-rainfall
origin under both ample and limited water supply, indicating a higher water consumption that might increase competitiveness
in drought-prone habitats. Although most parameters tested were significantly influenced by genotype and treatment, the genotype
× treatment interactions were not significant. The genotypes differed in plasticity of the tested parameters and in their
apparent adaptation to drought; however, among genotypes, physiological plasticity and drought adaptation were not related
to each other. Reduction of gs was the first and most plastic response to drought in all genotypes, and allowed the maintenance of high predawn leaf water
potentials during the drought. None of the clones exhibited non-stomatal limitation of photosynthesis. Leaf gs, photosynthetic capacity, magnitude of osmotic adjustment and δ13C were all markedly lower in 2000 than in 1999, indicating root limitation in the containers in the second year.
Keywords:
δ13C, drought stress, gas exchange, leaf conductance, osmotic adjustment, phenotypic plasticity.
