Thermoimaging as a tool for studying light-induced heating of leaves : Correlation of heat dissipation with the efficiency of photosystem II photochemistry and non-photochemical quenching
2008
Kaňa, Radek | Vass, Imre
Thermoimaging - a highly sensitive and non-invasive method of temperature measurement - was applied to explore the role of changing photosynthetic efficiency in light-induced heating of tobacco (Nicotiana tabacum cv. Samsun) leaves. In the absence of evaporative cooling through the stomata, which was achieved by covering leaves with Vaseline, illumination with 50-1400μMphotonsm⁻² s⁻¹ intensity of photosynthetically active radiation resulted in [almost equal to]1-5°C leaf temperature increase in about 2min. The heating effect showed a non-linear correlation with the extent of non-photochemical quenching (NPQ) resulting in higher leaf temperatures at higher NPQ values. When leaves were adapted to excessive irradiance (1300μMphotonsm⁻² s⁻¹ for 6h), which resulted in reduction of photosynthetic efficiency and amplification of NPQ the light-induced heating effect was enhanced. The experimental results have been explained on the basis of a simple theoretical model characterizing the balance of energy fluxes in leaves in relation to the efficiency of photosystem II photochemistry and non-photochemical quenching. The role of alternative energy dissipation pathways outside of PSII in the phenomenon of light-induced leaf heating is also discussed.
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