Abstract
The photoprotection reaction of the photosynthetic system under excessive sun light has been resolved for the first time by femtosecond absorption spectroscopy from the visible to near-infrared in intact leaves of Arabidopsis thaliana . The light-adaptation process was measured and a prominent non-photochemical quenching (npq) behavior located in photosystem II was observed. Among the various npq quenching mechanisms which have been discussed so far the most likely is the formation of chlorophyll-chlorophyll charge-transfer states which create a powerful energy dissipation pathway for the quenching.
Highlights
Photosynthetic systems in natural environment are exposed to a wide range of incident light intensities which may change within seconds
The photoprotection reaction of the photosynthetic system under excessive sun light has been resolved for the first time by femtosecond absorption spectroscopy from the visible to near-infrared in intact leaves of Arabidopsis thaliana
In vivo femtosecond absorption measurements on intact leaves face a variety of severe technical obstacles: a) Scattering by coarse inhomogeneous structure inside leaves with their veins and chloroplast bodies virtually destroying laser beams, b) xy-scanning for averaging over a wider leaf area necessary to avoid local heating and photodamage, c) variations in the optical density from 0.1 to 2.0 in the leaf from spot to spot, d) production of oxygen bubbles leading to varying scatter during the measurements
Summary
Photosynthetic systems in natural environment are exposed to a wide range of incident light intensities which may change within seconds. The photoprotection reaction of the photosynthetic system under excessive sun light has been resolved for the first time by femtosecond absorption spectroscopy from the visible to near-infrared in intact leaves of Arabidopsis thaliana. The lightadaptation process was measured and a prominent non-photochemical quenching (npq) behavior located in photosystem II was observed.
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