Abstract
Upon termination of watering of plants of Nerium oleander exposed to high light, photochemical efficiency became reduced as leaf water content decreased. Evidence is presented that this type of photoinhibition reflects to a substantial degree radiationless dissipation of excitation energy, probably mediated by the carotenoid zeaxanthin. During the imposition of water stress, the zeaxanthin content of leaves increased at the expense of violaxanthin and β-carotene as a water deficit developed over a period of several days. The increase in zeaxanthin content was linearly related to an increase in the rate of radiationless energy dissipation in the antenna chlorophyll as calculated from the characteristics of chlorophyll a fluorescence measured with a pulse amplitude modulated fluorometer at room temperature. The increase in the rate of radiationless dissipation was also linearly related to a decrease in PSII photochemical efficiency as indicated by the ratio of variable to maximum fluorescence. Leaves of well-watered shade plants of N. oleander exposed to strong light showed a similar increase in zeaxanthin content as sun leaves of the same species subjected to drought in strong light. Shade leaves possessed the same capacity as sun leaves to form zeaxanthin at the expense of both violaxanthin and β-carotene. The resistance of this species to the destructive effects of excess light appears to be related to interconversions between β-carotene and the three carotenoids of the xanthophyll cycle.
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Selected References
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- Demmig B., Winter K., Krüger A., Czygan F. C. Photoinhibition and zeaxanthin formation in intact leaves : a possible role of the xanthophyll cycle in the dissipation of excess light energy. Plant Physiol. 1987 Jun;84(2):218–224. doi: 10.1104/pp.84.2.218. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Siefermann D., Yamamoto H. Y. Light-induced de-epoxidation of violaxanthin in lettuce chloroplasts. IV. The effects of electron-transport conditions on violaxanthin availability. Biochim Biophys Acta. 1975 Apr 14;387(1):149–158. doi: 10.1016/0005-2728(75)90059-6. [DOI] [PubMed] [Google Scholar]
- Weber A., Czygan F. C. Chlorophylle und Carotinoide der Chaetophorineae (Chlorophyceae, Ulotrichales). I. Siphonaxanthin in Microthamnion keutzingianum Naegeli. Arch Mikrobiol. 1972;84(3):243–253. [PubMed] [Google Scholar]
- Winter K., Demmig B. Reduction State of Q and Nonradiative Energy Dissipation during Photosynthesis in Leaves of a Crassulacean Acid Metabolism Plant, Kalanchoë daigremontiana Hamet et Perr. Plant Physiol. 1987 Dec;85(4):1000–1007. doi: 10.1104/pp.85.4.1000. [DOI] [PMC free article] [PubMed] [Google Scholar]