Zeaxanthin content and the degree of photoinhibition are linearly correlated in the brown algaDictyota dichotoma
✍ Scribed by S. Uhrmacher; D. Hanelt; W. Nultsch
- Publisher
- Springer-Verlag
- Year
- 1995
- Tongue
- English
- Weight
- 698 KB
- Volume
- 123
- Category
- Article
- ISSN
- 0025-3162
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✦ Synopsis
Photoinhibition of photosynthesis of the brown alga Dictyota dichotoma was studied by measuring changes of photosystem II fluorescence, oxygen production and xanthophyll pool (zeaxanthin, antheraxanthin and violaxanthin). The experiments were carried out with a pulse-amplitude modulation fluorometer (PAM), a homemade oxygen measuring device and high performance liquid chromatography (HPLC) for pigment analysis. Increasing fluences of a photoinhibitory white light caused a decrease of Fv/Fm (ratio of variable to maximal fluorescence), a decrease of oxygen production and concomitantly an increase in the contribution of zeaxanthin to the xanthophyll pool. Fv/Fm and oxygen production rate both showed a negative linear correlation to the zeaxanthinxanthophyll pool ratio of D. dichotoma. Dithiothreitol (DTT), an inhibitor of the de-epoxidase of the xanthophyll-cycle, suppressed the interconversion from violaxanthin to zeaxanthin and the decrease of the initial fluorescence (Fo) during strong-light irradiation. However, DTT was not able to prevent a decrease of Fv/Fm. With DTT, higher fluences of inhibitory white light were necessary to cause the same decrease of Fv/Fm as in the controls without DTT. The results indicate that the xanthophyll-cycle may play an important role in dynamic photoinhibition and recovery of photosynthesis in D. dichotoma.