Responses to desiccation stress in bryophytes and an important role of dithiothreitol-insensitive non-photochemical quenching against photoinhibition in dehydrated states.

Abstract

The effects of air drying and hypertonic treatments in the dark on seven bryophytes, which had grown under different water environments, were studied. All the desiccation-tolerant species tested lost most of their PSII photochemical activity when photosynthetic electron transport was inhibited by air drying, while, in all the sensitive species, the PSII photochemical activity remained at a high level even when photosynthesis was totally inhibited. The PSI reaction center remained active under drying conditions in both sensitive and tolerant species, but the activity became non-detectable in the light only in tolerant species due to deactivation of the cyclic electron flow around PSI and of the back reaction in PSI. Light-induced non-photochemical quenching (NPQ) was found to be induced not only by the xanthophyll cycle but also by a DeltapH-induced, dithiothreitol-insensitive mechanism in both the desiccation-tolerant and -intolerant bryophytes. Both mechanisms are thought to have an important role in protecting desiccation-tolerant species from photoinhibition under drying conditions. Fluorescence emission spectra at 77K showed that dehydration-induced quenching of PSII fluorescence was observed only in tolerant species and was due to neither state 1-state 2 transition nor detachment of light-harvesting chlorophyll protein complexes from PSII core complexes. The presence of dehydration-induced quenching of PSI fluorescence was also suggested.

• Authors: Hayase Nabe, Ryoko Funabiki, Yasuhiro Kashino, Hiroyuki Koike, Kazuhiko Satoh
• Journal: Plant & cell physiology (Plant Cell Physiol) Vol. 48 Issue 11 Pg. 1548-57 (Nov 2007) ISSN: 0032-0781 [Print] Japan
• PMID: 17908696 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Photosystem II Protein Complex
• Plant Proteins
• Water
• Chlorophyll
• Dithiothreitol

Topics

• Bryophyta (drug effects, metabolism, physiology)
• Chlorophyll (metabolism)
• Dithiothreitol (pharmacology)
• Electron Transport (drug effects, physiology, radiation effects)
• Fluorescence
• Photosynthesis (drug effects, physiology, radiation effects)
• Photosystem II Protein Complex (chemistry, metabolism)
• Plant Proteins (chemistry, metabolism)
• Water (metabolism, pharmacology)