<?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%">Tenhunen, J D</style></author><author><style face="normal" font="default" size="100%">Lange, O L</style></author><author><style face="normal" font="default" size="100%">Gebel, J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Changes in photosynthetic capacity, carboxylation efficiency, and CO 2 compensation point associated with midday stomatal closure and midday depression of net</style></title><secondary-title><style face="normal" font="default" size="100%">Planta</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Carboxylation efficiency</style></keyword><keyword><style  face="normal" font="default" size="100%">Compensation point (CO2)</style></keyword><keyword><style  face="normal" font="default" size="100%">Photosynthesis (temperature- humidity)</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus</style></keyword><keyword><style  face="normal" font="default" size="100%">Sclerophyll</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1984</style></year></dates><volume><style face="normal" font="default" size="100%">162</style></volume><pages><style face="normal" font="default" size="100%">193-203</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The carbon-dioxide response of photo- synthesis of leaves of Quercus suber, a sclerophyl- lous species of the European Mediterranean re- gion, was studied as a function of time of day at the end of the summer dry season in the natural habitat. To examine the response experimentally, a &quot;standard&quot; time course for temperature and hu- midity, which resembled natural conditions, was imposed on the leaves, and the CO 2 pressure exter- nal to the leaves on subsequent days was varied. The particular temperature and humidity condi- tions chosen were those which elicited a strong sto- matal closure at midday and the simultaneous de- pression of net CO 2 uptake. Midday depression of CO 2 uptake is the result of i) a decrease in CO2- saturated photosynthetic capacity after light satu- ration is reached in the early morning, ii) a de- crease in the initial slope of the CO 2 response curve (carboxylation efficiency), and iii) a substantial in- crease in the CO 2 compensation point caused by an increase in leaf temperature and a decrease in humidity. As a consequence of the changes in pho- tosynthesis, the internal leaf CO 2 pressure re- mained essentially constant despite stomatal clo- sure. The effects on capacity, slope, and compensa- tion point were reversed by lowering the tempera- ture and increasing the humidity in the afternoon. Constant internal CO 2 may aid in minimizing photoinhibition during stomatal closure at midday. The results are discussed in terms of possible tem- perature, humidity, and hormonal effects on pho- tosynthesis.</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%">Tenhunen, J D</style></author><author><style face="normal" font="default" size="100%">Lange, O L</style></author><author><style face="normal" font="default" size="100%">Braun, M</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Midday Stomatal Closure in Mediterranean Type Sclerophylls Under Simulated Habitat Conditions in an Environmental Chamber II. Effect of the Complex of Leaf Temperature and Air Humidity on Gas Exchange of Arbutus unedo and Quercus ilex</style></title><secondary-title><style face="normal" font="default" size="100%">Oecologia</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">midday stomatal closure</style></keyword><keyword><style  face="normal" font="default" size="100%">net photosynthetic rate (voyant)</style></keyword><keyword><style  face="normal" font="default" size="100%">transpiration rate</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">50</style></volume><pages><style face="normal" font="default" size="100%">5-11</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Shrubs of the Mediterranean sclerophyllous species Arbutus unedo and Quercus ilex were studied under simulated habitat conditions in an environmental chamber. Temperature, humidity, and light intensity were altered stepwise to simulate diurnal changes in conditions similar to those measured in an evergreen macchia in Sobreda, Portugal. Leaves were enclosed in cuvettes which reproduced the growth chamber climate and which allowed measurement of gas exchange. Increasing atmo- spheric stress in the form of higher temperature and lower humid- ity on successive days gradually results in midday depression of transpiration rate and net photosynthesis rate of leaves due to midday stomatal closure.</style></abstract></record></records></xml>