Zeaxanthin and the induction and relaxation kinetics of the dissipation of excess excitation energy in leaves in 2% O2, 0% CO2
Demmig-Adams, B. | Winter, K. | Kruger, A. | Czygan, F.C.
The relationship between the carotenoid zeaxanthin, formed by violaxanthin de-epoxidation, and nonphotochemical fluorescence quenching in the light was investigated in leaves of Glycine max during a transient from dark to light in 2% O2, 0% CO2 at 100 to 200 micromoles of photons per square meter per second. (a) Up to a nonphotochemical fluorescence quenching (which can vary between 0 and 1) of about 0.7, the zeaxanthin content of leaves was linearly correlated with nonphotochemical fluorescence quenching as well as with the rate constant for radiationless energy dissipation in the antenna chlorophyll (k(D)). Beyond this point, at very high degrees of fluorescence quenching, only k(D) was directly proportional to the zeaxanthin content. (b) The relationship between zeaxanthin and k(D) was quantitatively similar for the rapidly relaxing quenching induced in 2% O2, 0% CO2 at 200 micromoles of photons per square meter per second and for the sustained quenching induced by long-term exposure of Nerium oleander to drought in high light (B Demmig, K Winter, A Kruger, F-C Czygan [1988] Plant Physiol 87: 17-24). These findings suggest that the same dissipation process may be induced by very different treatments and that this particular dissipation process can have widely different relaxation kinetics. (c) A rapid induction of strong nonphotochemical fluorescence quenching within about 1 minute was observed exclusively in leaves which already contained a background level of zeaxanthin.
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