title: Costs of leaf reinforcement in response to winter cold in evergreen species.
abstract: The competitive equilibrium between deciduous and evergreen plant species to a large extent depends on the intensity of the reduction in carbon gain undergone by evergreen leaves, associated with the leaf traits that confer resistance to stressful conditions during the unfavourable part of the year. This study explores the effects of winter harshness on the resistance traits of evergreen leaves. Leaf mass per unit area (LMA), leaf thickness and the concentrations of fibre, nitrogen (N), phosphorus (P), soluble protein, chlorophyll and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) were determined in three evergreen and two deciduous species along a winter temperature gradient. In the evergreen species, LMA, thickness, and P and structural carbohydrate concentrations increased with the decrease in winter temperatures. Nitrogen and lignin concentrations did not show definite patterns in this regard. Chlorophyll, soluble proteins and Rubisco decreased with the increase in winter harshness. Our results suggest that an increase in LMA and in the concentration of structural carbohydrates would be a requirement for the leaves to cope with low winter temperatures. The evergreen habit would be associated with higher costs at cooler sites, because the cold resistance traits imply additional maintenance costs and reduced N allocation to the photosynthetic machinery, associated with structural reinforcement at colder sites.
authors.affiliation: Departamento de Ecología, Facultad de Biología, Universidad de Salamanca, 37071 Salamanca, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: González-Zurdo
authors.affiliation: Departamento de Ecología, Facultad de Biología, Universidad de Salamanca, 37071 Salamanca, Spain.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Escudero
authors.affiliation: Departamento de Fisiología Vegetal, Facultad de Biología, Universidad de Salamanca, 37071 Salamanca, Spain.
authors.forename: Josefa
authors.initials: J
authors.lastname: Babiano
authors.affiliation: Instituto de Recursos Naturales y Agrobiología (CSIC), 37071 Salamanca, Spain.
authors.forename: Antonia
authors.initials: A
authors.lastname: García-Ciudad
authors.affiliation: Departamento de Ecología, Facultad de Biología, Universidad de Salamanca, 37071 Salamanca, Spain ecomedv@usal.es.
authors.forename: Sonia
authors.initials: S
authors.lastname: Mediavilla
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D003080:Cold Temperature; D005843:Geography; D016014:Linear Models; D009584:Nitrogen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D018515:Plant Leaves / Q000033:anatomy & histology / Q000502:physiology*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D012621:Seasons; D013030:Spain; D013045:Species Specificity; D013696:Temperature; D014197:Trees / Q000502:physiology*
chemical_list: D002734:Chlorophyll; D010758:Phosphorus; D012273:Ribulose-Bisphosphate Carboxylase; D009584:Nitrogen
keywords: Rubisco; leaf fibre content; leaf mass per unit area; leaf thickness; nutrient content; winter temperature gradient