A powerful research technique is to simultaneously measure chlorophyll fluorescence and gas exchange to obtain a full picture of the response of plants to their environment. One technique is to simultaneously measure CO fixation and PSII photochemistry at different light intensities, in non-photorespiratory conditions. A plot of CO fixation and PSII photochemistry indicates the electron requirement per molecule CO fixed. From this estimation, the extent of photorespiration may be estimated. This has been used to explore the significance of photorespiration as a photoprotective mechanism during drought.
Fluorescence analysis can also be applied to understanding the effects of low and high temperatures.
* Sobrado (2008) investigated gas exchange and chlorophyll a fluorescence responses to high intensity light, of pioneer species and forest species. Midday leaf gas exchange was measured using a photosynthesis system, which measured net photosynthetic rate, gs, and intercellular CO concentration (). In the same leaves used for gas exchange measurements, chlorophyll a fluorescence parameters (initial, ; maximum, ; and variable, ) were measured using a fluorometer. The results showed that despite pioneer species and forest species occupying different habitats, both showed similar vulnerability to midday photoinhibition in sun-exposed leaves.