Zeaxanthin synthesis, energy dissipation, and photoprotection of photosystem II at chilling temperatures
1989
Demmig-Adams, B. | Winter, K. | Kruger, A. | Czygan, F.C.
When leaves of a mangrove, Rhizophora mangle, were exposed to an excess of light at chilling temperatures, synthesis of zeaxanthin through violaxanthin de-epoxidation as well as nonphotochemical fluorescence quenching were markedly reduced. The results suggest a protective role of energy dissipation against the adverse effects of high light and chilling temperatures: leaves of R. mangle that had been preilluminated in 2% O2, 0% CO2 at low photon flux density and showed a high level of zeaxanthin, and leaves that had been kept in the dark and contained no zeaxanthin, were both exposed to high light and chilling temperatures (5 degrees C leaf temperature) in air and then held under control conditions in low light in air at 25 degrees C. Measurements of chlorophyll a fluorescence at room temperature showed that the photochemical efficiency of PSII and the yield of maximum fluorescence of the preilluminated leaf recovered completely within 1 to 3 hours under the control conditions. In contrast, the fluorescence responses of the predarkened leaf in high light at 5 degrees C did not recover at all. During a dark/light transient in 2% O2, 0% CO2 in low light at 5 degrees C, nonphotochemical fluorescence quenching increased linearly with an increase in the zeaxanthin content in leaves of R. mangle. In soybean (Glycine max) leaves, which contained a background level of zeaxanthin in the dark, a similar treatment with excess light induced a level of nonphotochemical fluorescence quenching that was not paralleled by an increase in the zeaxanthin content.
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