<?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></contributors><titles><title><style face="normal" font="default" size="100%">Thermal optima of photosynthetic functions and thermostability of photochemistry in cork oak seedlings</style></title><secondary-title><style face="normal" font="default" size="100%">Tree Physiology</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2003</style></year></dates><volume><style face="normal" font="default" size="100%">23</style></volume><pages><style face="normal" font="default" size="100%">1031-1039</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Temperature effects on photosynthesis were studied in seedlings of evergreen Mediterranean cork oak (Quercus suber L.). Responses to changes in temperature and the temperature optima of maximal carboxylation rate (Vcmax) and maximal light-driven electron flux (Jmax) were estimated from gas exchange measurements and a leaf-level photosynthesis model. The estimated temperature optima were approximately 34 and 33 °C for Vcmax and Jmax, respectively, which fall within the lower range of temperature optima previously observed in deciduous tree species. The thermostability of the photosynthetic apparatus was estimated according to the temperature at which basal chlorophyll a fluorescence begins to increase (Tc). The Tc was highly variable, increasing from 42 to 51 °C when ambient temperature rose from 10 to 40 °C, and increasing from 44 to 54 °C with decreasing soil water availability while net CO2 assimilation rate dropped to almost zero. When a heat shock was imposed, an additional small increase in Tc was observed in drought-stressed and control seedlings. Maximal Tc values following heat shock were about 56 °C, which, to our knowledge, are the highest values that have been observed in tree species. In conclusion, the intrinsic temperature responses of cork oak did not differ from those of other species (similar Tc under ambient temperature and water availability, and relatively low thermal optima for photosynthetic capacity in seedlings grown at cool temperatures). However, the large ability of cork oak to acclimate to drought and elevated temperature may be an important factor in the tolerance of this evergreen Mediterranean species to summer drought and high temperatures.</style></abstract><notes><style face="normal" font="default" size="100%">10.1093/treephys/23.15.1031</style></notes><research-notes><style face="normal" font="default" size="100%">10.1093/treephys/23.15.1031</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%">Ghouil, Hana</style></author><author><style face="normal" font="default" size="100%">Montpied, Pierre</style></author><author><style face="normal" font="default" size="100%">Epron, Daniel</style></author><author><style face="normal" font="default" size="100%">Ksontini, Mustapha</style></author><author><style face="normal" font="default" size="100%">Hanchi, Belkacem</style></author><author><style face="normal" font="default" size="100%">Dreyer, Erwin</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Thermal optima of photosynthetic functions and thermostability of photochemistry in cork oak seedlings</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%">maximal carboxylation rate</style></keyword><keyword><style  face="normal" font="default" size="100%">maximal light-driven electron flow</style></keyword><keyword><style  face="normal" font="default" size="100%">Regeneration</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2003</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2003///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://treephys.oxfordjournals.org/content/23/15/1031.abstract</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">23</style></volume><pages><style face="normal" font="default" size="100%">1031 - 1039</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Temperature effects on photosynthesis were studied in seedlings of evergreen Mediterranean cork oak (Quercus suber L.). Responses to changes in temperature and the temperature optima of maximal carboxylation rate (Vcmax) and maximal light-driven electron flux (Jmax) were estimated from gas exchange measurements and a leaf-level photosynthesis model. The estimated temperature optima were approximately 34 and 33 °C for Vcmax and Jmax, respectively, which fall within the lower range of temperature optima previously observed in deciduous tree species. The thermostability of the photosynthetic apparatus was estimated according to the temperature at which basal chlorophyll a fluorescence begins to increase (Tc). The Tc was highly variable, increasing from 42 to 51 °C when ambient temperature rose from 10 to 40 °C, and increasing from 44 to 54 °C with decreasing soil water availability while net CO2 assimilation rate dropped to almost zero. When a heat shock was imposed, an additional small increase in Tc was observed in drought-stressed and control seedlings. Maximal Tc values following heat shock were about 56 °C, which, to our knowledge, are the highest values that have been observed in tree species. In conclusion, the intrinsic temperature responses of cork oak did not differ from those of other species (similar Tc under ambient temperature and water availability, and relatively low thermal optima for photosynthetic capacity in seedlings grown at cool temperatures). However, the large ability of cork oak to acclimate to drought and elevated temperature may be an important factor in the tolerance of this evergreen Mediterranean species to summer drought and high temperatures.</style></abstract><issue><style face="normal" font="default" size="100%">15</style></issue><notes><style face="normal" font="default" size="100%">10.1093/treephys/23.15.103110.1093/treephys/23.15.1031</style></notes></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors></contributors><titles><title><style face="normal" font="default" size="100%">Comparaison des effets de la contrainte hydrique sur la croissance, la conductance stomatique et la photosynthèse de jeunes plants de chênes méditerranéens (Quercus suber, Q. faginea, Q. coccifera) en Tunisie</style></title><secondary-title><style face="normal" font="default" size="100%">Ann. For. Sci.</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><volume><style face="normal" font="default" size="100%">55</style></volume><pages><style face="normal" font="default" size="100%">477-495</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Comparison of the water stress effects on stomatal conductance, photosynthesis and growth of Mediterannean oak seedlings (Quercus suber L., Q. faginea, Q. coccifera) in Tunisia. Two evergreen oaks (Quercus suber L., Q. coccifera) and one deciduous oak (Q. faginea Willd.) were subjected to drought in a nursery in Tunis. Six- and 18-month-old seedlings were grown in pots and underwent two cycles of drought by withholding water supply. Predawn and midday leaf water potentials, stomatal conductance, photosynthesis and plant transpiration were recorded. An analysis of root and shoot biomass, shoot-to-root ratio and leaf area was also performed. Our results showed a higher reduction of shoot-to-root biomass ratio of Q. faginea compared to Q. coccifera under water limitation. The stomatal conductance decrease, related to the decrease of predawn leaf water potential, occurred earlier with Q. faginea. Q. coccifera kept its stomata partly open at a water potential of -3.0 MPa. Q. suber behaved somewhat intermediate. Photosynthesis and stomatal conductance were correlated and showed a midday depression. Our results indicate that more ecophysiological studies are required to take into account seedling and leaf ages during the juvenile stage for a better understanding of the water stress responses of these species and regeneration problems of oaks.</style></abstract></record></records></xml>