Evaluation of the potential to measure photosynthetic rates in C3 plants (Flaveria pringlei and Oryza sativa) by combining chlorophyll fluorescence analysis and a stomatal conductance model

Abstract

ABSTRACTThe response curves of leaf photosynthesis to varying light, temperature and leaf‐to‐air vapour pressure deficit were measured in the C3 plants Flaveria pringlei and Oryza sativa in normal air with a computerized open infrared gas analysis (IRGA) system, and the photochemical efficiency of photosystem II, described as (1–F,/F′m) after Genty. Briantais & Baker (1989, Biochimica et Biophysica Acta 990, 87–92), was simultaneously measured with a modulated fluorometer. A model was written for rates of CO2 fixation as a function of the true rate of O2 evolution measured by fluorescene analysis (Jo2), mesophyll conductance and intercellular CO2 partial pressure. A second model was developed for rates of CO2 fixation as a function of Jo2, mesophyll conductance and stomatal conductance. In the latter case, leaf stomatal conductance was simulated using the stomatal model proposed by Leuning (1995, Plant, Cell and Environment18, 339–355). The rates of CO2 fixation predicted from the models were similar to rates measured by IRGA. The results indicate that there is potential to measure CO2 fixation in C3 plants by combining the non‐invasive measurement of Jo2 by chlorophyll fluorescence analysis with the stomatal conductance model.