In vivo thermal energy dissipation was photoacoustically monitored in pea leaves before and after strong light treatment. Concomitant with the conversion of the carotenoid violaxanthin into zeaxanthin, a marked increase in the heat emission signal was observed in the light-stressed leaves. However, when the xanthophyll cycle was blocked by dithiothreitol, the photothermal signal still increased, indicating that there was no causal relationship between these two phenomena. Increased heat emission was shown to result from pigment uncoupling, which caused the inhibition of the energy transfer from carotenoids to chlorophyrs. It was also observed that the maintenance of a very low zeaxanthin level by dithiothreitol led to an increase in both the oxygen evolution and the photothermal components of the photoacoustic signal in control leaves and to a strong increase in lipid degradation in light-stressed leaves. These results may suggest that a possible function of the xanthophyll cycle is to provide an accessory pigment (violaxanthin) in weak light and to furnish the hpid matrix of the thylakoid membranes with an efficient photoprotector (zeaxanthin) in strong light.
|Original language||English (US)|
|Number of pages||10|
|Journal||Journal of Photochemistry and Photobiology, B: Biology|
|State||Published - Mar 1991|
- Heat emission
- xanthophyll cycle.
ASJC Scopus subject areas
- Plant Science
- Physical and Theoretical Chemistry