Relationship between photosynthesis and respiration in leaves using 13C/12C isotope labelling

Abstract

The relationship between photosynthesis and respiration was studied in four plant species (Ranunculus glacialis, Chamaerops humilis, Phaseolus vulgaris and Fagus sylvatica) using 13C/12C stable isotopes. This study was conducted using an open gas-exchange system coupled to an elemental analyzer and linked to an isotope ratio mass spectrometer (IRMS). We showed that the carbon recently assimilated during photosynthesis accounts for ca. 50% of the carbon in the CO2 lost by dark respiration after illumination in Phaseolus vulgaris and Fagus sylvatica, and less than 10% in Ranunculus glacialis and Chamaerops humilis. Therefore, most of the carbon released by dark respiration after illumination in leaves does not come from ‘new’ photosynthates.