Improving respiration measurements with gas exchange analyzers

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 (ΔCO₂) 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 ΔCO₂. Therefore, it can be concluded that leaf position is important to guarantee the improvement of respiration measurements increasing ΔCO₂ 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.

Keywords: Amphistomatous leaf; Dark respiration; Gas exchange analyzer; Hypostomatous leaf; Overlapping leaves.