Abstract

Dark respiration measurements with open-flow gas exchange analyzers are often questioned for their low accuracy as their low values often reach the precision limit of the instrument. Respiration was measured in five species, two hypostomatous (Vitis Vinifera L. and Acanthus mollis) and three amphistomatous, one with similar amount of stomata in both sides (Eucalyptus citriodora) and two with different stomata density (Brassica oleracea and Vicia faba). CO2 differential (Delta CO2) increased two-fold with no change in apparent R-d, when the two leaves with higher stomatal density faced outside. These results showed a clear effect of the position of stomata on Delta CO2. Therefore, it can be concluded that leaf position is important to guarantee the improvement of respiration measurements increasing Delta CO2 without affecting the respiration results by leaf or mass units. This method will help to increase the accuracy of leaf respiration measurements using gas exchange analyzers. (C) 2016 Elsevier GmbH. All rights reserved.