Using a reaction‐diffusion model to estimate day respiration and reassimilation of (photo)respired CO₂ in leaves

Abstract

Summary Methods using gas exchange measurements to estimate respiration in the light (day respiration ) make implicit assumptions about reassimilation of (photo)respired CO 2 ; however, this reassimilation depends on the positions of mitochondria. We used a reaction‐diffusion model without making these assumptions to analyse datasets on gas exchange, chlorophyll fluorescence and anatomy for tomato leaves. We investigated how values obtained by the Kok and the Yin methods are affected by these assumptions and how those by the Laisk method are affected by the positions of mitochondria. The Kok method always underestimated . Estimates of by the Yin method and by the reaction‐diffusion model agreed only for nonphotorespiratory conditions. Both the Yin and Kok methods ignore reassimilation of (photo)respired CO 2 , and thus underestimated for photorespiratory conditions, but this was less so in the Yin than in the Kok method. Estimates by the Laisk method were affected by assumed positions of mitochondria. It did not work if mitochondria were in the cytosol between the plasmamembrane and the chloroplast envelope. However, mitochondria were found to be most likely between the tonoplast and chloroplasts. Our reaction‐diffusion model effectively estimates , enlightens the dependence of estimates on reassimilation and clarifies (dis)advantages of existing methods.

The Kok effect revisited

“…Berghuijs et al . (2019) showed that R d estimated by the Kok method was closer to the estimate made by their model (that accounted for the refixation) under nonphotorespiratory than under photorespiratory conditions. The experiment of Loreto et al .…”

Unravelling mechanisms and impacts of day respiration in plant leaves: an introduction to a Virtual Issue

“…Berghuijs et al . (2019) elaborated on the 2D model of photosynthetic cells described in Berghuijs et al . (2017) and used observed values of A to predict maximal carboxylation ( V cmax ) and R light by fitting.…”

“…One advantage of this technique is that it is independent of g m , thus providing a way of estimating R light , and in turn, assisting in calculating values of g m and c c . Berghuijs et al (2019) elaborated on the 2D model of photosynthetic cells described in Berghuijs et al (2017) and used observed values of A to predict maximal carboxylation (V cmax ) and R light by fitting. This technique assumes a certain geometry of the…”

“…(2018), Abadie & Tcherkez (2019), Berghuijs et al . (2019), Dusenge et al . (2019), Kumarathunge et al .…”

The Impact of Photorespiratory Glycolate Oxidase Activity on Arabidopsis thaliana Leaf Soluble Amino Acid Pool Sizes during Acclimation to Low Atmospheric CO2 Concentrations

“…Photorespiration has been seen as a wasteful process since it leads to a potential loss of assimilated carbon and nitrogen and it has an energetic cost since released CO 2 can diffuse to the chloroplast to be re-assimilated [ 6 ] and photorespiratory NH 3 can be re-assimilated by the glutamine synthase/glutamine:2-oxoglutarate aminotransferase (GS/GOGAT) cycle [ 7 ]. However, photorespiration is crucial for plant growth in air as seen from studies of photorespiratory mutants that exhibit various deleterious symptoms including dwarfism, chlorosis, and plant death [ 8 ].…”