Inhibition of photosynthetic processes in foliose lichens induced by temperature and osmotic stress.
| Authors | |
|---|---|
| Year of publication | 2006 |
| Type | Article in Periodical |
| Magazine / Source | Biologia Plantarum |
| MU Faculty or unit | |
| Citation | |
| Field | Botany |
| Keywords | photosynthesis; water potential; dehydration; Lasallia pustulata; Umbilicaria hirsuta; sucrose; chlorophyll fluorescence; thallus anatomy |
| Description | Negative effects of osmotically-induced dehydration of two foliose lichen species, Lasallia pustulata and Umbilicaria hirsuta, was studied at physiological (22 deg C), low (5 deg C) and freezing temperature (-10 deg C), using chlorophyll (Chl) fluorescence. In both species, exposition to increasing sucrose concentrations led to a pronounced decrease in potential (FV/FM), and actual (Fi2) quantum yields of photochemical processes in photosystem 2. Lasallia pustulata was more sensitive to osmotic stress, because comparable osmotic dehydration inhibited FV/FM, Fi2 more than in Umbilicaria hirsuta. In our study, critical concentration of sucrose that fully inhibited photochemical processes of photosynthesis was 2.5 M, which represented water potential (ŁZ) of ĄV18.8 MPa. Decrease in background Chl fluorecsence (F0) and increase in non-photochemical quenching (qN) revealed two phases of osmotic stress in lichens: phase I with no change (ŁZ 0 to -6.6 MPa) and phase II (ŁZ -11.3 to -18.8 MPa) typical by substantial change in Chl fluorescence parameters. Effects of thallus anatomy on species-specific response to osmotic dehydration is discussed and attributed to results obtained by optical microscopy and Chl fluorescence imaging technique. |
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