title: Responses to desiccation stress in lichens are different from those in their photobionts.
abstract: In order to clarify the role of symbiotic association in desiccation tolerance of photosynthetic partners in lichens, responses to air-drying and hypertonic treatments in a green-algal lichen (a chlorolichen, Ramalina yasudae Räsänen) and its green algal photobiont (freshly released and cultured Trebouxia sp.) were studied. Responses to dehydration in the isolated Trebouxia sp. were different from those in the lichen, R. yasudae, i.e. (i) the PSII reaction was totally inhibited in R. yasudae when photosynthesis was completely inhibited by desiccation, but it remained partially active in isolated Trebouxia sp; (ii) dehydration-induced quenching of PSII fluorescence was less in the isolated Trebouxia sp. compared with that in R. yasudae, suggesting that a substance(s) or a mechanism(s) to dissipate absorbed light energy to heat was lost by the isolation of the photobiont; and (iii) the air-dried isolated Trebouxia sp. showed a higher sensitivity to photoinhibition than R. yasudae. These results support the idea that association of the photobionts with the mycobionts increases tolerance to photoinhibition under drying conditions.
authors.affiliation: Department of Life Science, School of Life Science, University of Hyogo, Harima Science Garden City, Hyogo 678-1297, Japan.
authors.forename: Makiko
authors.initials: M
authors.lastname: Kosugi
authors.forename: Maiko
authors.initials: M
authors.lastname: Arita
authors.forename: Ryoko
authors.initials: R
authors.lastname: Shizuma
authors.forename: Yufu
authors.initials: Y
authors.lastname: Moriyama
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kashino
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Koike
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Satoh
mesh_terms: D000460:Chlorophyta / Q000502:physiology* / Q000528:radiation effects; D003890:Desiccation; D005453:Fluorescence; D008011:Lichens / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D013559:Symbiosis
chemical_list: D045332:Photosystem II Protein Complex