© 2007 Heron Publishing—Victoria, Canada
Water-use efficiency in cork oak (Quercus suber) is modified by the interaction of water and light availabilities
Ismael Aranda (1,2), Marta Pardos (1), Jaime Puértolas (3), Maria Dolores Jiménez (4) and Jose Alberto Pardos (4)
1. Centro de Investigación Forestal (CIFOR), Instituto Nacional de Investigación Agraria y Tecnología Agroalimentaria, Carretera
Coruña Km., 7´5, 28040 Madrid, Spain / 2. Corresponding author (aranda@inia.es) / 3. Centro Nacional de Mejora Forestal. “El Serranillo”, DGB, Ministerio de Medio Ambiente, Apdo 249 19004, Guadalajara, Spain / 4. Unidad de Anatomía, Fisiología y Genética Forestal, Escuela Técnica Superior Ingenieros de Montes, Universidad Politécnica
de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain / Received November 15, 2005; accepted May 10, 2006; published online February 1, 2007
Summary
We studied the interaction of light and water on water-use efficiency in cork oak (Quercus suber L.) seedlings. One-year-old cork oak seedlings were grown in pots in a factorial experiment with four light treatments (68,
50, 15 and 5% of full sunlight) and two irrigation regimes: well watered (WW) and moderate drought stress (WS). Leaf predawn
water potential, which was measured at the end of each of two cycles, did not differ among the light treatments. Water-use
efficiency, assessed by carbon isotope composition (δ13C), tended to increase with increasing irradiance. The trend was similar in the WW and WS treatments, though with lower δ13C in all light treatments in the WW irrigation regime. Specific leaf area increased with decreasing irradiance, and was inversely
correlated with δ13C. Thus, changes in δ13C could be explained in part by light-induced modifications in leaf morphology. The relationship between stomatal conductance
to water vapor and net photosynthesis on a leaf area basis confirmed that seedlings in higher irradiances maintained a higher
rate of carbon uptake at a particular stomatal conductance, implying that shaded seedlings have a lower water-use efficiency
that is unrelated to water availability.
Keywords:
carbon isotope composition, uptake, drought, specific leaf area, photosynthesis, shade, stomatal conductance, water potential.
