A simple alternative approach to assessing the fate of absorbed light energy using chlorophyll fluorescence

We propose a simplified alternative method for quantifying the partitioning of excitation energy between photochemistry, fluorescence and thermal dissipation. This alternative technique uses existing well-defined quantum efficiencies such as _{PS II}, leaving no 'excess' efficiency unaccounted for, effectively separates regulated and constitutive thermal dissipation processes, does not require the use of F _o and F′ _o measurements and gives very similar results to the method proposed by Kramer et al. [(2004) Photosynth Res 79: 209-218]. We demonstrate the use of the technique using chlorophyll fluorescence measurements in grapevine leaves and observe a high dependence on thermal dissipation processes (up to 75%) at both high light and low temperature.