Modeling leaf CO 2 assimilation and Photosystem II photochemistry from chlorophyll fluorescence and the photochemical reflectance index

Abstract

We present a simple model to assess the quantum yield of photochemistry (Φ P ) and CO 2 assimilation rate from two parameters that are detectable by remote sensing: chlorophyll (chl) fluorescence and the photochemical reflectance index (PRI). Φ P is expressed as a simple function of the chl fluorescence yield (Φ F ) and nonphotochemical quenching (NPQ): Φ P  = 1–bΦ F (1 + NPQ). Because NPQ is known to be related with PRI, Φ P can be remotely assessed from solar-induced fluorescence and the PRI. The CO 2 assimilation rate can be assessed from the estimated Φ P value with either the maximum carboxylation rate (V cmax ), the intercellular CO 2 concentration (C i ), or parameters of the stomatal conductance model. The model was applied to experimental data obtained for Chenopodium album leaves under various environmental conditions and was able to successfully predict Φ F values and the CO 2 assimilation rate. The present model will improve the accuracy of assessments of gas exchange rates and primary productivity by remote sensing.