Involvement of xanthophyll cycle pigments and glutathione in photoprotection of lichen <i>Umbilicaria antarctica<i>
| Authors | |
|---|---|
| Year of publication | 2004 |
| Type | Article in Proceedings |
| Conference | 14th International congress on photobiology, June 10-15, 2004, Program & Abstracts |
| MU Faculty or unit | |
| Citation | |
| Field | Botany |
| Keywords | high light stress; lichens; zeaxanthin; glutathione; chlorophyll fluorescence |
| Description | High light (HL) stress could be expected even in HL-adapted lichens when their thalli, cells of symbiotic photobiont in particular, are exposed to HL in wet state. Among several physiological photoprotective mechanisms activated during such situations, conversion of violaxanthin to zeaxanthin (Z) and capacity of glutathione (GSH) pool are of major importance. Until now, however, changes in GSH pool and its redox state have been studied in lichens only in relation to water stress. Our experiments focused on changes in Z (expressed as de-epoxidation state of xanthophyll cycle pigments - DEPS) and GSH during HL stress imposed on Umbilicaria antarctica. HL stress was induced by applying a strong light of 1800 umol m-2 s-1 for 30 min on hydrated thalli of U. antarctica at 20degC. Timecourse of HL stress and recovery was monitored by chlorophyll fluorescence (maximal quantum yield, Fv/Fm, non-photochemical quenching, NPQ). HL stress led to a photoinhibition demonstrated as a decrease of Fv/Fm and an increase in NPQ. During subsequent 10 h recovery under low light, Fv/Fm and NPQ recovered almost to pre-photoinhibitory levels. HL-induced increase in DEPS, maximum of which was recorded immediately after HL exposure. Then, DEPS decreased during 10 h to initial level. Total GSH strongly decreased after HL and proportion of its oxidised to reduced form slightly increased. During 10 h recovery, total GSH did not increase to initial value indicating that re-synthesis of GSH was not completed. |
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