<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Ceacero, Carlos J</style></author><author><style face="normal" font="default" size="100%">Navarro-cerrillo, Rafael M</style></author><author><style face="normal" font="default" size="100%">Díaz-Hernández, José Luis</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Is tree shelter protection an effective complement to weed competition management in improving the morpho-physiological response of holm oak planted seedlings?</style></title><secondary-title><style face="normal" font="default" size="100%">iForest - Biogeosciences and Forestry</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Mulch</style></keyword><keyword><style  face="normal" font="default" size="100%">Oxyfluorfen</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">photosynthesis</style></keyword><keyword><style  face="normal" font="default" size="100%">Tillage</style></keyword><keyword><style  face="normal" font="default" size="100%">tree shelter</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2014</style></year></dates><pages><style face="normal" font="default" size="100%">275-285</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Weed control is a key aspect that influences seedling response in newly-established plantations. Tree shelter protection may be an effective complement to weed control with a positive effect on the overall response of seedlings. Our study focused on assessing the morpho-physiological response of Holm oak (Quercus ilex L. ballota [Desf.] Samp.) plantations to weed control and individual protection as a combined cultural technique on a cropland site in southern Spain. The weed control treatments (cultivation, herbicide and mulch) were also applied in combination with tree shelters. Morpho-physiological variables including survival, aerial and root morphology, water potential, gas exchange and chlorophyll fluorescence were monitored over a 2-year period. Results showed that weed competition management treatments improved the seedling survival rate compared to the control treatment. Moreover, shelter was associated with a greater height growth. At early stages of establishment, and particularly under combined treatments, all plants invested more resources in their aerial parts than in their root system. Seedlings did not regulate water loss as a result of water stress, contrary to what would be expected in Mediterranean areas. Under all treatments, especially those combined with tree shelters, seedlings took up to 2 years to achieve morpho-physiological adaptation (i.e. height and diameter growths, water stress behavior) to site conditions. In addition, tree shelters promoted an increase in net photosynthesis compared to non-shelter treatments during the winter period. The tree shelters also limited the emergence of photo-inhibition phenomena in seedlings so that plants under combined treatments showed greater photo-chemical efficiency. Thus, this study supports the effectiveness of tree shelter protection as a complement to weed control treatments. More specifically, it suggests that combining individual protection (shelter) and weed control around seedlings is an interesting technique for reforestation of forest ecosystems in Mediterranean areas.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Ceacero, Carlos J.</style></author><author><style face="normal" font="default" size="100%">Díaz, José Luis</style></author><author><style face="normal" font="default" size="100%">del Campo, Antonio D.</style></author><author><style face="normal" font="default" size="100%">Navarro-Cerrillo, Rafael M. ª</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Evaluación temprana de técnicas de restauración forestal mediante fluorescencia de la clorofila y diagnóstico de vitalidad de brinzales de encina (Quercus ilex sub. ballota)</style></title><secondary-title><style face="normal" font="default" size="100%">Bosque (Valdivia)</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">control de competencia herbácea</style></keyword><keyword><style  face="normal" font="default" size="100%">fotoinhibición</style></keyword><keyword><style  face="normal" font="default" size="100%">herbaceous competition control</style></keyword><keyword><style  face="normal" font="default" size="100%">photochemical efficiency</style></keyword><keyword><style  face="normal" font="default" size="100%">photochemical eficiency</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">rendimiento fotoquímico</style></keyword><keyword><style  face="normal" font="default" size="100%">tree shelter</style></keyword><keyword><style  face="normal" font="default" size="100%">tubo invernadero</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2012</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2012///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.scielo.cl/scielo.php?script=sci_arttext&amp;pid=S0717-92002012000200009&amp;lng=en&amp;nrm=iso&amp;tlng=en</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">33</style></volume><pages><style face="normal" font="default" size="100%">17 - 18</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Chlorophyll a luorescence has been applied to study the evolution of leaf photoprotection processes to dissipate excess absorbed energy that can not be fully utilized in photochemical reactions, and relects the plants ability to adapt to environmental conditions. Plants environmental conditions can be modiied by forest restoration techniques to ensure successful seedlings establishment, hence chlorophyll a luorescence can be a useful tool for assessing plant response to planting stress. The objective of this paper was to analyze the chlorophyll a luorescence as an early indicator of oak seedling response to the establishment stress and as a useful tool for the assessment of different competition control and individualized protection techniques (tillage, herbicide, mulch, tree shelter) used in forest restoration. A ield experimental plot with these restoration treatments was established and a monthly monitoring of chlorophyll a luorescence and a vitality analysis were carried out between August 2003 and October 2004 on oak seedlings. Results showed that luorescence parameters were sensitive to stress conditions prevailing in each analysed period. On the evaluation of herbaceous competition control techniques, no signiicant results on the chlorophyll a luorescence were observed. However, tree shelters exercised a protection effect on seedling limiting the photoinhibition processes during spring and winter periods. Finally, protected plants showed major photochemical eficiency than that showed by unprotected ones according to vitality tests. Therefore, the chlorophyll a luorescence analysis was proved to be a useful tool for early assessment of oak seedlings establishment stress and for the assessment of certain forest restoration techniques, such as those that combine control of herbaceous competition and individualized seedling protection.</style></abstract><issue><style face="normal" font="default" size="100%">2</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Holland, V.</style></author><author><style face="normal" font="default" size="100%">Brüggemann, W.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Photosynthetic properties of Quercus × hispanica Lam. and Q. suber L. under harsh Central European winter conditions</style></title><secondary-title><style face="normal" font="default" size="100%">Photosynthetica</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">evergreen</style></keyword><keyword><style  face="normal" font="default" size="100%">frost stress</style></keyword><keyword><style  face="normal" font="default" size="100%">oak</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">xanthophyll cycle</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2011</style></year></dates><volume><style face="normal" font="default" size="100%">49</style></volume><pages><style face="normal" font="default" size="100%">459-465</style></pages><isbn><style face="normal" font="default" size="100%">1109901100</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In search for new forestation tree species for future Central European climate conditions, Mediterranean evergreen oak taxa are investigated for their summer drought- and winter frost-hardiness. Here we report on the winter performance of the photosynthetic apparatus of Quercus × hispanica Lam. and its evergreen parental species Q. suber L. under extraordinary harsh winter conditions. Both taxa showed a strong decline of photosystem II (PSII) quantum efficiency (Fv/Fm) with a concomitant increase in the deepoxidation state (DES) of the xanthophyll pigments depending on (severe) frost events during winter, and these parameters significantly correlated with minimum air temperatures during periods of chronic photoinhibition at mid-winter, but not at the onset of winter in response to the first frost nights. Fv/Fm and DES correlated with each other in both taxa throughout the winter.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Brüggemann, Wolfgang</style></author><author><style face="normal" font="default" size="100%">Bergmann, Michael</style></author><author><style face="normal" font="default" size="100%">Nierbauer, Kai-Uwe</style></author><author><style face="normal" font="default" size="100%">Pflug, Ellen</style></author><author><style face="normal" font="default" size="100%">Schmidt, Carlo</style></author><author><style face="normal" font="default" size="100%">Weber, Daniel</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Photosynthesis studies on European evergreen and deciduous oaks grown under Central European climate conditions: II. Photoinhibitory and light-independent violaxanthin deepoxidation and downregulation of photosystem II in evergreen, winter-acclimated Euro</style></title><secondary-title><style face="normal" font="default" size="100%">Trees</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">á downregulation of ps</style></keyword><keyword><style  face="normal" font="default" size="100%">chlororespiration</style></keyword><keyword><style  face="normal" font="default" size="100%">chlororespiration á photoinhibition á</style></keyword><keyword><style  face="normal" font="default" size="100%">downregulation of ps II</style></keyword><keyword><style  face="normal" font="default" size="100%">ii</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus</style></keyword><keyword><style  face="normal" font="default" size="100%">quercus á winter acclimation</style></keyword><keyword><style  face="normal" font="default" size="100%">winter acclimation</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><volume><style face="normal" font="default" size="100%">23</style></volume><pages><style face="normal" font="default" size="100%">1091-1100</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In the context of the search for future forestry species in Central Europe under climate change scenarios, the evergreen Mediterranean Quercus taxa Q. ilex ssp. ilex and Q. suber and the semideciduous hybrids. Q. 9 turneri and Q. 9 hispanica were studied in relation to their photochemical efﬁciency of photosystem II and to the activity of the xanthophyll cycle under Central European winter conditions. The evergreen taxa were remarkably insensitive to winter stress in the ﬁeld and reacted towards frost periods with the phenomenon of ‘‘chronic photoinhibition’’, i.e. a decrease in pre-dawn Fv/Fm and an increase in the deepoxidation state of the xanthophylls. Under dark and warmer conditions (room temperature), winter-acclimated leaves of the evergreen taxa except for Q. 9 turneri produced zeaand antheraxanthin and decreased Fv/Fm, possibly by creation of a chlororespiratory pH-gradient. It is suggested that the ability for dark violaxanthin deepoxidation may contribute to the winter hardiness of the evergreen taxa.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Brüggemann, Wolfgang</style></author><author><style face="normal" font="default" size="100%">Bergmann, Michael</style></author><author><style face="normal" font="default" size="100%">Nierbauer, Kai-Uwe</style></author><author><style face="normal" font="default" size="100%">Pflug, Ellen</style></author><author><style face="normal" font="default" size="100%">Schmidt, Carlo</style></author><author><style face="normal" font="default" size="100%">Weber, Daniel</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Photosynthesis studies on European evergreen and deciduous oaks grown under Central European climate conditions: II. Photoinhibitory and light-independent violaxanthin deepoxidation and downregulation of photosystem II in evergreen, winter-acclimated Euro</style></title><secondary-title><style face="normal" font="default" size="100%">Trees</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">á downregulation of ps</style></keyword><keyword><style  face="normal" font="default" size="100%">chlororespiration</style></keyword><keyword><style  face="normal" font="default" size="100%">chlororespiration á photoinhibition á</style></keyword><keyword><style  face="normal" font="default" size="100%">downregulation of ps II</style></keyword><keyword><style  face="normal" font="default" size="100%">ii</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus</style></keyword><keyword><style  face="normal" font="default" size="100%">quercus á winter acclimation</style></keyword><keyword><style  face="normal" font="default" size="100%">winter acclimation</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2009///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://link.springer.com/10.1007/s00468-009-0351-yhttp://www.springerlink.com/index/10.1007/s00468-009-0351-y</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">23</style></volume><pages><style face="normal" font="default" size="100%">1091 - 1100</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In the context of the search for future forestry species in Central Europe under climate change scenarios, the evergreen Mediterranean Quercus taxa Q. ilex ssp. ilex and Q. suber and the semideciduous hybrids. Q. 9 turneri and Q. 9 hispanica were studied in relation to their photochemical efﬁciency of photosystem II and to the activity of the xanthophyll cycle under Central European winter conditions. The evergreen taxa were remarkably insensitive to winter stress in the ﬁeld and reacted towards frost periods with the phenomenon of ‘‘chronic photoinhibition’’, i.e. a decrease in pre-dawn Fv/Fm and an increase in the deepoxidation state of the xanthophylls. Under dark and warmer conditions (room temperature), winter-acclimated leaves of the evergreen taxa except for Q. 9 turneri produced zeaand antheraxanthin and decreased Fv/Fm, possibly by creation of a chlororespiratory pH-gradient. It is suggested that the ability for dark violaxanthin deepoxidation may contribute to the winter hardiness of the evergreen taxa.</style></abstract><issue><style face="normal" font="default" size="100%">5</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gómez-Aparicio, LORENA</style></author><author><style face="normal" font="default" size="100%">Valladares, Fernando</style></author><author><style face="normal" font="default" size="100%">Zamora, Regino</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Differential light responses of Mediterranean tree saplings: linking ecophysiology with regeneration niche in four co-occurring species</style></title><secondary-title><style face="normal" font="default" size="100%">Tree Physiology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Acer opalus subsp. granatense</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">photosynthetic light response</style></keyword><keyword><style  face="normal" font="default" size="100%">Pinus nigra</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus ilex</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus pyrenaica</style></keyword><keyword><style  face="normal" font="default" size="100%">shade tolerance</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2006</style></year></dates><volume><style face="normal" font="default" size="100%">26</style></volume><pages><style face="normal" font="default" size="100%">947-958</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The ecophysiological mechanisms underlying plant–plant interactions and forest regeneration processes in Mediterranean ecosystems are poorly understood, and the experimental evidence for the role of light availability in these processes is particularly scant. We analyzed the effects of high and low irradiances on 31 ecological, morphological and physiological variables in saplings of four late-successional Mediterranean trees, two deciduous (Acer opalus subsp. granatense (Boiss.) Font Quer &amp; Rothm. and Quercus pyrenaica Willd.) and two evergreen (Pinus nigra Arnold subsp. salzmannii (Dunal) Franco and Quercus ilex L.), which coexist in mature montane forests. Species differed in both their capacity to withstand high radiation and in their shade tolerance. The two deciduous species were the least tolerant to high radiation, exhibiting both dynamic and chronic photoinhibition in full sunlight, with severe implications for gas exchange and photosynthetic performance. Excess light severely limited the survival of A. opalus subsp. granatense, even minor reductions of excessive radiation (from full sunlight to 80% sunlight) being crucial for sapling survival. Among species, P. nigra was the most tolerant of high irradiances but showed the poorest shade acclimation. Interspecific differences in the mechanisms of response to light provide a partial explanation of the differential regeneration patterns previously reported for these species, with shade-tolerant plants (i.e., deciduous broadleaf species) benefiting the most from associations with nurse plants. We conclude that light availability is an important environmental factor defining the regeneration niche of Mediterranean woody species.</style></abstract><notes><style face="normal" font="default" size="100%">10.1093/treephys/26.7.947</style></notes><research-notes><style face="normal" font="default" size="100%">10.1093/treephys/26.7.947</style></research-notes></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Oliveira, G.</style></author><author><style face="normal" font="default" size="100%">Penuelas, J.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of winter cold stress on photosynthesis and photochemical efficiency of PSII of the Mediterranean Cistus albidus L. and Quercus ilex L.</style></title><secondary-title><style face="normal" font="default" size="100%">Plant Ecology</style></secondary-title><short-title><style face="normal" font="default" size="100%">Plant Ecol</style></short-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">evergreen</style></keyword><keyword><style  face="normal" font="default" size="100%">Fv/Fm</style></keyword><keyword><style  face="normal" font="default" size="100%">Mediterranean winter</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">semi-deciduous</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2005</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2005/01/01</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://dx.doi.org/10.1007/s11258-005-4876-x</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Kluwer Academic Publishers</style></publisher><volume><style face="normal" font="default" size="100%">175</style></volume><pages><style face="normal" font="default" size="100%">179-191</style></pages><isbn><style face="normal" font="default" size="100%">1385-0237</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><issue><style face="normal" font="default" size="100%">2</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Oliveira, G</style></author><author><style face="normal" font="default" size="100%">Penuelas, J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of winter cold stress on photosynthesis and photochemical efficiency of PSII of the Mediterranean Cistus albidus L. and Quercus ilex L.</style></title><secondary-title><style face="normal" font="default" size="100%">Plant Ecology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">evergreen</style></keyword><keyword><style  face="normal" font="default" size="100%">Fv/Fm</style></keyword><keyword><style  face="normal" font="default" size="100%">Mediterranean winter</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">semi-deciduous</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2004</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2004///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/index/GV5P7326829Q0GK6.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">175</style></volume><pages><style face="normal" font="default" size="100%">179 - 191</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">This study examined the photosynthetic and growth performances of potted plants of Cistus albidus L. and Quercus ilex L. submitted either to natural Mediterranean winter conditions or to mild greenhouse conditions. Plants grown outdoors exhibited lower light and CO2 -saturated CO2 assimilation rates Asat and apparent quantum yield i than those indoors. Until mid-winter, C. albidus had higher Asat than Q. ilex, but differences disappeared after a period of severe cold. Maximal photochemical efficiency of PSII Fv/Fm measured predawn was higher in C. albidus than in Q. ilex, and decreased throughout the season in outdoor plants. Fv/Fm also decreased at light saturation Asat in both species. Fv/Fm was correlated with photosynthetic capacity and efficiency quantum yield, but the resulting regression slopes were different between the two species. At the physiological level, C. albidus seemed to cope better with cold stress than Q. ilex. However, winter stress induced reduction of leaf absorptance, increased leaf mass per area, extensive leaf damage and high plant mortality in C. albidus. This suggests that the high performance of C. albidus leaves is not likely to be maintained for long periods of cold stress, and may therefore depend on continuous leaf replacement. Quercus ilex showed a conservative behaviour, with low net assimilation rates but greater leaf and plant survival than C. albidus.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Oliveira, G</style></author><author><style face="normal" font="default" size="100%">Penuelas, J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Comparative photochemical and phenomorphological responses to winter stress of an evergreen ( Quercus ilex L.) and a semi-deciduous ( Cistus albidus</style></title><secondary-title><style face="normal" font="default" size="100%">Acta Oecologica</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Chlorophyll ﬂuorescence</style></keyword><keyword><style  face="normal" font="default" size="100%">evergreens</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf characteristics</style></keyword><keyword><style  face="normal" font="default" size="100%">Mediterranean winter</style></keyword><keyword><style  face="normal" font="default" size="100%">Phenology</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">semi-deciduous</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2000///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science/article/pii/S1146609X00001211</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">21</style></volume><pages><style face="normal" font="default" size="100%">97 - 107</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The impact of winter stress on plants from a Mediterranean area was evaluated through comparison of photosystem II (PS II) efficiencies and phenomorphological characteristics of two Mediterranean woody species – Quercus ilex (evergreen) and Cistus albidus (semi-deciduous). The studies were carried out in NE Spain, at two sites with different mean winter temperatures. The results showed that reductions of the efficiency of PS II may occur in Mediterranean plant communities during winter, and are especially remarkable on colder days. The extent and duration of the decrease in PS II efficiency (photoinhibition) depended not only on the climatic conditions, but also on the site, on the species considered and on the position of leaves in the plant canopy. Increased photoinhibition at the colder site was only clear for C. albidus. Nevertheless, the efficiencies of PS II were always higher in C. albidus than in Q. ilex. Phenological patterns, morphology and leaf inclination may protect C. albidus leaves from potentially photoinhibitory conditions in winter. Morphological and structural photoprotection is apparently not so well developed in Q. ilex, which probably relies more on increased protection at the photochemical level of its long-lived leaves. As has been reported in relation to summer-drought stress, Q. ilex has possibly developed a strategy of tolerance to photoinhibition, whereas C. albidus relies preferentially on avoidance features</style></abstract><issue><style face="normal" font="default" size="100%">2</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Garcia-Plazaola, J I</style></author><author><style face="normal" font="default" size="100%">Artetxe, Unai</style></author><author><style face="normal" font="default" size="100%">BECERRIL, J M</style></author><author><style face="normal" font="default" size="100%">Garcı, Ignacio</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Diurnal changes in antioxidant and carotenoid composition in the Mediterranean schlerophyll tree Quercus ilex(L) during winter</style></title><secondary-title><style face="normal" font="default" size="100%">Plant Science</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Holm oak</style></keyword><keyword><style  face="normal" font="default" size="100%">low-temperature stress</style></keyword><keyword><style  face="normal" font="default" size="100%">Mediterranean evergreens</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">photoprotection</style></keyword><keyword><style  face="normal" font="default" size="100%">xanthophyll cycle</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><volume><style face="normal" font="default" size="100%">143</style></volume><pages><style face="normal" font="default" size="100%">125-133</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Seasonal changes of pigment composition and antioxidant content were characterized in the Mediterranean evergreen holm oak (Quercus ilex L.). Higher contents of antioxidants and carotenoids, with a photoprotective role during winter, indicated that this period was highly stressful, so a study of diurnal changes in photosynthesis, pigments and carotenoids was conducted during January in sun and shade leaves. Sun and shade leaves were used to compare the effects due only to low temperature separate from those resulting from the interaction of light. During winter, a relatively high rate of CO2 ﬁxation on sun leaves represented an important sink for photosynthetic electrons contributing to the annual carbon balance of the plant. This high rate contrasted with a reduced Fv :Fm, even at predawn. This reduction was correlated with the accumulation of zeaxanthin at the expense of violaxanthin by de-epoxidation. Sun leaves were also protected by a higher concentration of antioxidants (ascorbate, glutathione and tocopherol) and carotenoids (except lutein epoxide). Ascorbate was 10–50-fold greater than the other antioxidants, indicating a central role in protection against photooxidative stress. Nevertheless those mechanisms were unable to avoid a loss of hydrophilic antioxidants (glutathione and ascorbate) and xanthophylls during the initial morning hours after dawn, indicating that the ﬁrst target of photooxidative damage was these molecules</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">García-Plazaola, J. I.</style></author><author><style face="normal" font="default" size="100%">Artetxe, Unai</style></author><author><style face="normal" font="default" size="100%">BECERRIL, J. M.</style></author><author><style face="normal" font="default" size="100%">Garcı, Ignacio</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Diurnal changes in antioxidant and carotenoid composition in the Mediterranean schlerophyll tree Quercus ilex(L) during winter</style></title><secondary-title><style face="normal" font="default" size="100%">Plant Science</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Holm oak</style></keyword><keyword><style  face="normal" font="default" size="100%">low-temperature stress</style></keyword><keyword><style  face="normal" font="default" size="100%">Mediterranean evergreens</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">photoprotection</style></keyword><keyword><style  face="normal" font="default" size="100%">xanthophyll cycle</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1999///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science/article/pii/S0168945299000345</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">143</style></volume><pages><style face="normal" font="default" size="100%">125 - 133</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Seasonal changes of pigment composition and antioxidant content were characterized in the Mediterranean evergreen holm oak (Quercus ilex L.). Higher contents of antioxidants and carotenoids, with a photoprotective role during winter, indicated that this period was highly stressful, so a study of diurnal changes in photosynthesis, pigments and carotenoids was conducted during January in sun and shade leaves. Sun and shade leaves were used to compare the effects due only to low temperature separate from those resulting from the interaction of light. During winter, a relatively high rate of CO2 ﬁxation on sun leaves represented an important sink for photosynthetic electrons contributing to the annual carbon balance of the plant. This high rate contrasted with a reduced Fv :Fm, even at predawn. This reduction was correlated with the accumulation of zeaxanthin at the expense of violaxanthin by de-epoxidation. Sun leaves were also protected by a higher concentration of antioxidants (ascorbate, glutathione and tocopherol) and carotenoids (except lutein epoxide). Ascorbate was 10–50-fold greater than the other antioxidants, indicating a central role in protection against photooxidative stress. Nevertheless those mechanisms were unable to avoid a loss of hydrophilic antioxidants (glutathione and ascorbate) and xanthophylls during the initial morning hours after dawn, indicating that the ﬁrst target of photooxidative damage was these molecules</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fleck, I</style></author><author><style face="normal" font="default" size="100%">Hogan, K P</style></author><author><style face="normal" font="default" size="100%">Llorens, L</style></author><author><style face="normal" font="default" size="100%">Abadía, A</style></author><author><style face="normal" font="default" size="100%">Aranda, X</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Photosynthesis and photoprotection in Quercus ilex resprouts after fire</style></title><secondary-title><style face="normal" font="default" size="100%">Tree Physiology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">chlorophyll fluorescence</style></keyword><keyword><style  face="normal" font="default" size="100%">Gas exchange</style></keyword><keyword><style  face="normal" font="default" size="100%">Holm oak</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">Photosystem II</style></keyword><keyword><style  face="normal" font="default" size="100%">zeaxanthin</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><volume><style face="normal" font="default" size="100%">18</style></volume><pages><style face="normal" font="default" size="100%">607-614</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Plants that resprout after fires often have higher rates of photosynthesis than before a fire. To elucidate the mechanism of this response, we studied gas exchange and chlorophyll fluorescence in Quercus ilex L. plants growing on control (unburned) sites and on sites that had been burned the preceding summer. In early July, photosynthetic rates and stomatal conductance were similar in plants on unburned and burned plots, and in young and old foliage within unburned plots. At this time, photochemical efficiency of photosystem II (PSII), nonphotochemical quenching of chlorophyll fluorescence (NPQ), and the de-epoxidation of violaxanthin to zeaxanthin were also similar among leaves of different ages and treatments. In late July, photosynthetic rates and stomatal conductances were much greater in resprouts on the burned areas than in unburned plants. From early to late July, unburned plants showed an increase in NPQ and the de-epoxidation of violaxanthin to zeaxanthin, indicating increased photoprotection as a result of enhanced nonradiative dissipation of excess light energy. Plants on the burned plots did not show these changes. Leaves of all ages and treatments showed no substantial reduction in potential quantum yield of PSII (Fv/Fm) at midday or predawn, indicating that there was little or no photoinhibition. Leaf nitrogen and soluble protein contents varied with leaf age during July, but did not vary between treatments. We conclude that the primary effect of burning is an increase in water availability to resprouting plants that eliminates the need for photoprotection, at least in the short term. The decrease in photosynthetic rates of unburned leaves in late July was the result of reduced stomatal conductance. We suggest that lowered stomatal conductance is the primary limiting factor in Q. ilex leaves, governing the regulation of carboxylation activity and energy dissipation processes.</style></abstract><notes><style face="normal" font="default" size="100%">10.1093/treephys/18.8-9.607</style></notes><research-notes><style face="normal" font="default" size="100%">10.1093/treephys/18.8-9.607</style></research-notes></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Faria, T</style></author><author><style face="normal" font="default" size="100%">Garcia-Plazaola, J I</style></author><author><style face="normal" font="default" size="100%">Abadía, A</style></author><author><style face="normal" font="default" size="100%">Cerasoli, S</style></author><author><style face="normal" font="default" size="100%">Pereira, J S</style></author><author><style face="normal" font="default" size="100%">Chaves, M M</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Diurnal changes in photoprotective mechanisms in leaves of cork oak (Quercus suber) during summer</style></title><secondary-title><style face="normal" font="default" size="100%">Tree Physiology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">antioxidants</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">photosynthesis</style></keyword><keyword><style  face="normal" font="default" size="100%">Stomatal conductance</style></keyword><keyword><style  face="normal" font="default" size="100%">xanthophylls</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><volume><style face="normal" font="default" size="100%">16</style></volume><pages><style face="normal" font="default" size="100%">115-123</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Daily variations in photoprotective mechanisms were studied in sun and shade leaves of 40-year-old cork oak (Quercus suber L.) trees during early summer in Portugal. Although trees were not severely water stressed because predawn leaf water potentials remained high, photosynthesis and stomatal conductance decreased at midday. The midday depression in gas exchange was not reversed by short-term exposure to “optimal” conditions of temperature, light and vapor pressure deficit. Chlorophyll a fluorescence, maximum photochemical yield of photosystem II and the quantum yield of noncyclic electron transport showed midday depressions, but recovered by the evening. Both short-term changes in the components of the xanthophyll cycle (reversible de-epoxidation of violaxanthin during the day) as well as long-term changes (higher xanthophyll content in sun compared with shade leaves) were detected and may play a role in the dissipation of excess energy at midday. Because the activities of enzymes of the antioxidant system, superoxide dismutase and ascorbate peroxidase, were high enough to cope with the increase in oxygen reactive species likely to arise under the stressful conditions of midday, we conclude that these enzymes may provide an additional mechanism for energy dissipation.</style></abstract><notes><style face="normal" font="default" size="100%">10.1093/treephys/16.1-2.115</style></notes><research-notes><style face="normal" font="default" size="100%">10.1093/treephys/16.1-2.115</style></research-notes></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Méthy, M</style></author><author><style face="normal" font="default" size="100%">Damesin, C</style></author><author><style face="normal" font="default" size="100%">Rambal, S</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Drought and photosystem II activity in two Mediterranean oaks</style></title><secondary-title><style face="normal" font="default" size="100%">Ann. For. Sci.</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">fluorescence</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">Photosystem II</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus</style></keyword><keyword><style  face="normal" font="default" size="100%">water stress</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><volume><style face="normal" font="default" size="100%">53</style></volume><pages><style face="normal" font="default" size="100%">255-262</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The responses of photosystem II (PS II) to drought were analysed on two Mediterranean oak species, Quercus ilex and Q pubescens, using the chlorophyll fluorescence pulse-amplitude-modulation technique. The maximal PS II photochemical efficiency (Fv/Fm) of the evergreen Q ilex and the deciduous Q pubescens oaks was only affected when leaf predawn water potential was lower than -4 MPa. This value is rarely observed on mature trees growing in the field, but can be undergone by young seedlings during drought periods, hence confirming the stability of PS II. Whatever the irradiance, drought resulted, in both species, in lower values of PS II photochemical efficiency in a light-adapted state (ΔF/F m'), due to stomatal closure and/or a direct inhibition of the dark reactions of photosynthesis. Diurnal decreases of Fv/Fm of 30 min dark-adapted leaves were greater for lower predawn water potential; a recovery was observed in the late afternoon. The reversible decreases in the diurnal time-courses of maximal fluorescence led us to assume the onset of protective mechanisms from permanent photodamages in Q ilex and, to a lesser extent, in Q pubescens.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Epron, D</style></author><author><style face="normal" font="default" size="100%">Dreyer, E</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Stomatal and non stomatal limitation of photosynthesis by leaf water deficits in three oak species: a comparison of gas exchange and chlorophyll a fluorescence data</style></title><secondary-title><style face="normal" font="default" size="100%">Ann. For. Sci.</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Chlorophyll a fluorescence</style></keyword><keyword><style  face="normal" font="default" size="100%">Drought</style></keyword><keyword><style  face="normal" font="default" size="100%">oak</style></keyword><keyword><style  face="normal" font="default" size="100%">photoinhibition</style></keyword><keyword><style  face="normal" font="default" size="100%">photosynthesis</style></keyword><keyword><style  face="normal" font="default" size="100%">Stomatal conductance</style></keyword><keyword><style  face="normal" font="default" size="100%">water stress</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1990</style></year></dates><volume><style face="normal" font="default" size="100%">47</style></volume><pages><style face="normal" font="default" size="100%">435-450</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Net CO2 assimilation (A), stomatal conductance for CO2 (g), intercellular mole fraction of CO2 (Ci), kinetics of chlorophyll a fluorescence, and their half decay time (t1/2), their ratio of fluorescence decrease (Rfd), and their adaptive index (Ap) have been monitored on potted trees from 3 oak species (Quercus petraea, Q pubescens and Q ilex) grown in a climate chamber and submitted to drought. Use of A vs Ci representations for photosynthesis data revealed an apparent impairment of mesophyll photosynthesis, together with reduced CO2 supply to mesophyll due to stomatal closure. But in all species chlorophyll a fluorescence kinetics displayed very similar shapes, constant t1/2 and stable Rfd and Ap values until predawn leaf water potential dropped below -4.0 MPa. These observations led to the conclusion that photochemical energy conversion and photosynthetic carbon reduction cycle could be very resistant to leaf water deficits, and that observed decreases in mesophyll photosynthesis had to be attributed to a possible artefact in Ci calculation. On the other hand, the susceptibility of leaves to photoinhibition increased as a consequence of water shortage, especially in Q petraea and Q pubescens. Differences in drought adaptation between the studied species could probably be related to susceptibility to photoinhibition rather than to a direct sensitivity of photosynthesis to leaf water deficits, at least in the range of stress intensities of ecophysiological significance.</style></abstract></record></records></xml>