Combined Gas Exchange
& Fluorescence

With the LI-6400XT and Leaf Chamber Fluorometer you can simultaneously measure gas exchange and fluorescence over the same leaf area.

Gas exchange and fluorescence measurements quantify the gross CO2 assimilation (AG) and the quantum efficiency of photosystem (PS) II-mediated electron transport (ΦPSII). When combined with measurements of irradiance (i), leaf absorbance (α), and the fraction of light partitioned to PSII (fII), ΦPSII can be used to quantify the process of electron transfer that produces the chemical energy (ATP and NADPH) needed to assimilate CO2 and power other biochemical processes.

Application Page:

chlorophyll fluorescenceChlorophyll

Application Note:
Stressed Plants?

The Importance of Measuring Leaf Fluorescence

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Comparison of electron transfer rate (ETR) and AG provides quantitative information about the energy used to assimilate CO2 (Figure 1). Deviations from the theoretical coupling between ETR and AG indicate the consumption of chemical energy or the diversion of electrons into processes other than CO2 assimilation that may occur under certain environmentally stressful conditions.

Gas Exchange & Fluorescence graphs

Figure 1. Electron transfer rate (ETR) as a function of gross CO2 assimilation (AG) for leaves in 2% oxygen and 21% oxygen. The low oxygen level (2%) suppresses photorespiration (slope=5.0; R2=0.99), resulting in greater CO2 fixation per electron than high oxygen levels (slope=6.9; R2=0.99).

6400-40 Leaf Chamber Fluorometer

The Leaf Chamber Fluorometer is a pulse-amplitude modulated (PAM) fluorometer that can be used to take measurements on both dark- and light-adapted leaves. Measured parameters include Fo, Fm, F, Fs, Fm′, and Fo′, and calculated parameters include Fv, Fv/Fm, Fv′/Fm′, ΦPSII, ΔF/Fm′, qP, qN, NPQ, and ETR.
The unique design of the Leaf Chamber Fluorometer eliminates the need for fiber optic light guides. The system features portability and low power consumption so one person can gather data quickly and easily.


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