title: Low temperature during winter elicits differential responses among populations of the Mediterranean evergreen cork oak (Quercus suber).
abstract: Populations of cork oak (Quercus suber L.) were assessed for seasonal and inter-population variability in, and temperature responses of, the ratio between light-induced variable and maximum fluorescence of chlorophyll, Fv/Fm, considered a surrogate for the maximum photochemical efficiency of photosystem II (PSII). Seedlings from 10 populations throughout the distribution range of Q. suber in the Mediterranean basin were grown in a common garden in central Spain. The Fv/Fm ratio of dark-adapted leaves was measured at dawn every month for 2 years. Air temperature was recorded at a nearby climatic station. During the summer, when maximum air temperatures reached 40 degrees C, there were no significant differences in Fv/Fm among populations, but significant differences were seen during the winter. In colder months, Fv/Fm ranged in all populations between 0.5-0.6 and 0.2-0.3 in 2001 and 2002, respectively. The variance explained by the population effect was greatest during winter months, especially in 2002, reaching a peak value of 10% when minimum air temperature was below -10 degrees C. Populations originating from warmer sites showed the largest decline in Fv/Fm between the end of 2001 and the beginning of 2002. Thus, a negative linear relationship was established between mean annual temperature at the population source and population mean Fv/Fm recorded in the coldest month in 2002 and normalized by the Fv/Fm spring measurement.
authors.affiliation: Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Carretera de la Coruña Km., 7.5, 28040 Madrid, Spain. aranda@inia.es
authors.forename: I
authors.initials: I
authors.lastname: Aranda
authors.forename: L
authors.initials: L
authors.lastname: Castro
authors.forename: R
authors.initials: R
authors.lastname: Alía
authors.forename: J A
authors.initials: JA
authors.lastname: Pardos
authors.forename: L
authors.initials: L
authors.lastname: Gil
mesh_terms: D003080:Cold Temperature; D017753:Ecosystem; D019083:Mediterranean Region; D010788:Photosynthesis / Q000502:physiology; D045332:Photosystem II Protein Complex / Q000378:metabolism; D029963:Quercus / Q000378:metabolism*; D012621:Seasons; D013997:Time Factors
chemical_list: D045332:Photosystem II Protein Complex