Photoacoustic study of non-photochemical quenching in methylviologen treated dandelion leaves

The potential of photoacoustic (PA) spectroscopy for monitoring non-photochemical quenching was investigated. Intact and methylviologen treated selected dandelion (Taraxacum officinale ) leaves, previously adapted to darkness, were suddenly illuminated with light. The PA signals of intact leaves were shown to remain constant during induction of photosynthesis at low intensity of light. Under high light conditions,a noticeable decrease in the heat emission yield was observed, resulting from progressive activation of photochemical processes. The photothermal signals in methylviologen treated leaves were shown to substantially decrease during induction of photosynthesis. The large variability in PA signal kinetics allowed us to determine the "decrease ratio and the characteristic time of non-photochemical quenching. The results, obtained under varyiation of illuminating light, were compared to the data from fluorescence quenching of photosynthesis induction.