Activation of non-photochemical quenching in thylakoids and leaves |
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Authors: | Giles N. Johnson Andrew J. Young Peter Horton |
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Affiliation: | (1) Robert Hill Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, P.O. Box 594, S10 2UH Sheffield, UK;(2) School of Biological and Earth Sciences, John Moores University Liverpool, Byrom Street, L3 3AF Liverpool, UK;(3) Present address: Institut für Botanik, Westfälische Wilhelms-Universität, D-48149 Münster, Germany |
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Abstract: | The mechanism of rapidly-relaxing non-photochemical quenching in two plant species,Chenopodium album L. andDigitalis purpurea L., that differ considerably in their capacity for such quenching has been investigated (Johnson G.N. et al. 1993, Plant Cell Environ.16, 673–679). Illumination of leaves of both species in the presence of 2% O2 balance N2 led to the formation of zeaxanthin. When thylakoids were isolated from leaves of each species that had been so treated it was found that inD. purpurea non-photochemical quenching was “activated” relative to the control; a higher level of quenching was found for a given trans-thylakoid pH gradient. No such activation of non-photochemical quenching was observed inC. album. Similar conclusions were drawn when comparing quenching in intact leaves. It is concluded that light activation of quenching is a process that cannot readily be induced inC. album. Measurement of the sensitivity of non-photochemical quenching in leaves ofC. album andD. purpurea to dithiothreitol (DTT; a reagent that inhibits formation of zeaxanthin) showed differences between the two species. In both cases, feeding leaves with DTT inhibited the light-induced formation of zeaxanthin. InC. album this was accompanied by complete inhibition of reversible non-photochemical quenching, whereas inD. purpurea this inhibition was only partial. Data are discussed in relation to studies on the mechanism of quenching and the role of zeaxanthin in this process. |
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Keywords: | Chlorophyll fluorescence Chenopodium Digitalis Non-photochemical quenching Photosynthesis Xanthophyll cycle Zeaxanthin |
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