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Zaragoza, Spain

Forest trees in Mediterranean continental areas undergo both summer and winter stress. Recent large-scale studies of regeneration patterns of pine and oak species have reported the expansion of Quercus ilex to the detriment of pine species. To asses this trend from a physiological point of view, we compared the effect of summer and winter stress on the photochemical apparatus of the co-occurring species Pinus pinaster and Q. ilex ssp. ballota. We measured P. pinaster net photosynthetic rates and photosystem II (PS II) photochemical efficiency after summer and compared them with previous results obtained for P. pinaster after winter and for Q. ilex after summer and winter. Pinus pinaster and Q. ilex displayed contrasting photochemical efficiencies and heat dissipation after winter and summer. Pinus pinaster showed a lower fraction of photochemically active PS II reaction centres and lower effective quantum yield of the PS II photochemistry, accompanied by a higher dissipation of absorbed light energy as heat in the PS II antenna complexes. Quercus ilex showed the opposite, which was reflected in its higher photosynthetic rates. Our results support the advance of Q. ilex to the detriment of P. pinaster under the climate change scenario in Mediterranean areas. We discuss the results in the context of forest succession and climate change. The second objective of this study was to evaluate the effectiveness of the chlorophyll fluorescence technique to detect intraspecific differences in P. pinaster photochemical efficiency after summer stress. PS II photochemical parameters discriminated among families and populations, especially under limiting conditions (xeric site). Most of the genetic variation was explained by the family and its interaction with the environment and was higher in the xeric site. The significant heritabilities and differences among families within populations in actual photochemical efficiency (ΦPSII) and non-photochemical quenching (NPQ) and their interaction with the environment suggest that photochemical responses to summer stress are genetically inherited and that adaptive variation is maintained within populations due to local selection. Consequently, these parameters could be used for the selection of more tolerant genotypes to summer photoinhibition. © 2015 © Institute of Chartered Foresters, 2015. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com. Source

Corcuera L.,Forest Resources Unit | Gil-Pelegrin E.,Forest Resources Unit | Notivol E.,Forest Resources Unit

As part of a program to select maritime pine (Pinus pinaster Ait.) genotypes for resistance to low winter temperatures, we examined variation in photosystem II activity by chlorophyll fluorescence. Populations and families within populations from contrasting climates were tested during two consecutive winters through two progeny trials, one located at a continental and xeric site and one at a mesic site with Atlantic influence. We also obtained the LT 50, or the temperature that causes 50% damage, by controlled freezing and the subsequent analysis of chlorophyll fluorescence in needles and stems that were collected from populations at the continental trial site. P. pinaster showed sensitivity to winter stress at the continental site, during the colder winter. The combination of low temperatures, high solar irradiation and low precipitation caused sustained decreases in maximal photochemical efficiency (F v/F m), quantum yield of non-cyclic electron transport (Φ PSII) and photochemical quenching (qP). The variation in photochemical parameters was larger among families than among populations, and population differences appeared only under the harshest conditions at the continental site. As expected, the environmental effects (winter and site) on the photochemical parameters were much larger than the genotypic effects (population or family). LT 50 was closely related to the minimum winter temperatures of the population's range. The dark-adapted F v/F m ratio discriminated clearly between interior and coastal populations. In conclusion, variations in F v/F m, Φ PSII, qP and non-photochemical quenching (NPQ) in response to winter stress were primarily due to the differences between the winter conditions and the sites and secondarily due to the differences among families and their interactions with the environment. Populations from continental climates showed higher frost tolerance (LT 50) than coastal populations that typically experience mild winters. Therefore, LT 50, as estimated by F v/F m, is a reliable indicator of frost tolerance among P. pinaster populations. © 2011 Corcuera et al. Source

Corcuera L.,Forest Resources Unit | Gil-Pelegrin E.,Forest Resources Unit | Notivol E.,Forest Resources Unit | Tognetti R.,Forest Resources Unit
Tree Physiology

We studied the intraspecific variability of maritime pine in a set of morphological and physiological traits: soil-to-leaf hydraulic conductance, intrinsic water-use efficiency (WUE, estimated by carbon isotope composition, d13C), root morphology, xylem anatomy, growth and carbon allocation patterns. The data were collected from Pinus pinaster Aiton seedlings (25 half-sib families from five populations) grown in a greenhouse and subjected to water and water-stress treatments. The aims were to relate this variability to differences in water availability at the geographic location of the populations, and to study the potential trade-offs among traits. The drought-stressed seedlings demonstrated a decrease in hydraulic conductance and root surface area and increased WUE and root tip number. The relationships among the growth, morphological, anatomical and physiological traits changed with the scale of study: within the species, among/within populations. The populations showed a highly significant relationship between the percentage reduction in whole-plant hydraulic conductance and WUE. The differences among the populations in root morphology, whole-plant conductance, carbon allocation, plant growth and WUE were significant and consistent with dryness of the site of seed origin. The xeric populations exhibited lower growth and a conservative water use, as opposed to the fast-growing, less water-use-efficient populations from mesic habitats. The xeric and mesic populations, Tamrabta and San Cipriano, respectively, showed the most contrasting traits and were clustered in opposite directions along the main axis in the canonical discriminant analysis under both the control and drought treatments. The results suggest the possibility of selecting the Arenas population, which presents a combination of traits that confer increased growth and drought resistance. © 2012 The Author 2012. Source

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