<?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%">Gabriel, Reinhard</style></author><author><style face="normal" font="default" size="100%">Kesselmeier, Jürgen</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Apoplastic Solute Concentrations of Organic Acids and Mineral Nutrients in the Leaves of Several Fagaceae</style></title><secondary-title><style face="normal" font="default" size="100%">Plant and Cell Physiology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Anions</style></keyword><keyword><style  face="normal" font="default" size="100%">Apoplast</style></keyword><keyword><style  face="normal" font="default" size="100%">cations</style></keyword><keyword><style  face="normal" font="default" size="100%">Fagaceae</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf</style></keyword><keyword><style  face="normal" font="default" size="100%">organic acids</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://pcp.oxfordjournals.org/content/40/6/604.abstract</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">40</style></volume><pages><style face="normal" font="default" size="100%">604 - 612</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Ion chromatographic methods determined organic acids and main nutrient minerals in the apoplastic solution from leaves of several Fagaceae (Quercus ilex L., Quercus cerris L., Quercus virgiliana (Ten.) Ten, and Fagus sylvatica L.). The anions of organic acids found in high amounts (250 to 650 μM) were quinate, malate, and oxalate. Lactate, pyruvate, formate and acetate were detected in relatively low amounts with concentrations between 20 and 200 μM. The total concentration of organic acids in the apoplastic sap ranged between 1.5 and 2 mM. The total concentration of inorganic cations (K+, Mg2+, NH4+, Ca2+, Na+) and anions (C1−, NO3−, SO2−4 and PO3−4) in the apoplastic sap varied between 5 and 10 mM, and 0.35 and 1.8 mM, respectively. We conclude that the concentration of organic acid ions in the leaf apoplast depends mainly on the exchange with the leaf cells and is influenced by the electrochemical gradient between the symplast and the apoplast in relation to the water potential of the leaf. The determination of formate and acetate in the apoplastic compartment of leaves lend weight to the argument that the production of these acids by trees is a important emission source to the atmosphere.</style></abstract><issue><style face="normal" font="default" size="100%">6</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%">Gabriel, R.</style></author><author><style face="normal" font="default" size="100%">Schäfer, L.</style></author><author><style face="normal" font="default" size="100%">Gerlach, C.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Factors controlling the emissions of volatile organic acids from leaves of Quercus ilex L.(Holm oak)</style></title><secondary-title><style face="normal" font="default" size="100%">Atmospheric Environment</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">aba abscisic acid</style></keyword><keyword><style  face="normal" font="default" size="100%">Gas exchange</style></keyword><keyword><style  face="normal" font="default" size="100%">organic acids</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus ilex</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/S1352231098003690</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">33</style></volume><pages><style face="normal" font="default" size="100%">1347 - 1355</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Direct emissions and emission of precursor compounds of acetic and formic acid from higher plants are a signiÞcant source of these acids in the atmosphere. To travel from the plant cell to the atmosphere, a gas molecule must Þrst leave the liquid phase and then enter the internal leaf gas phase. The apoplast (cell wall) is the last barrier before the molecule can escape through the stomata. During Þeld experiments we monitored the gas exchange (H 2 O, CO 2 , organic acids) of Quercus ilex L. leaves. The exchange rates of acetic and formic acid under Þeld conditions followed a typical diurnal pattern and ranged between!10 (uptake) and 52 (emission) nmol m~2 leaf area min~1 with the maximum around noon. Growth chamber experiments indicate that the emission is related to the stomatal conductance. We discussed the exchange rate of organic acids between the cell wall and the atmosphere in connection with HenryÕs law, and the physicochemical conditions in the cell wall. The evaluation showed that for apoplastic pH values between 4 and 5, 26Ð130% of the measured acetic acid emission based on leaf area could be predicted. ( 1999 Elsevier Science Ltd. All rights reserved.</style></abstract></record></records></xml>