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Chlorophyll Fluorescence of Lichens Containing Green and Blue‐Green Algae During Hydration by Water Vapor Uptake and by Addition of Liquid Water *
Author(s) -
Lange O. L.,
Bilger W.,
Rimke S.,
Schreiber U.
Publication year - 1989
Publication title -
botanica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 0932-8629
DOI - 10.1111/j.1438-8677.1989.tb00110.x
Subject(s) - chlorophyll fluorescence , photosynthesis , algae , fluorescence , lichen , chemistry , water vapor , yield (engineering) , dehydration , humidity , botany , biology , materials science , organic chemistry , biochemistry , quantum mechanics , physics , metallurgy , thermodynamics
The fluorescence yield at room temperature of the lichens Ramalina maciformis and Peltigera rufescens , containing either green or blue‐green algae (Cyanobacteria) as phycobionts, has been investigated during rehydration of the dry lichens by water vapor uptake or by wetting with liquid water. In the dry state the fluorescence yield with all reaction centers open, F o , was low and no variable fluorescence could be induced with both species. Whereas R. maciformis , containing green algae, regained normal fluorescence behavior during water vapor uptake, the photosynthetic apparatus of the blue‐green algae‐containing P. rufescens stayed inhibited and could be reactivated only by addition of liquid water. During stepwise rehydration at increasing air humidities, a pattern was established for the recovery of the different fluorescence parameters in R. maciformis . At a dry‐weight related water content between 30 and 40%, F o rose sharply. Maximal variable fluorescence yield expressed as (F v ) m /F o , strongly increased in the same range of water content and remained constant above a water content of 50%. Non‐photochemical fluorescence quenching, q NP , determined at the end of a period of actinic illumination, decreased with increasing water vapor uptake. While spraying the lichen with liquid water did not induce a further decrease of q NP , slow dehydration at lowered air humidity led to a minimal value of q NP at a water content of 65 % indicating optimal photosynthetic rate under these conditions. These results extend the conclusions drawn from earlier gas exchange experiments that blue‐green algae‐containing lichens are unable to reactivate photosynthesis by water vapor uptake. During a re‐ and de‐hydration cycle, no hysteresis in the hydration dependence of the fluorescence parameters was found. From this and the presence of a stable and low F o value at prolonged incubation in nearly water vapor saturated air, we conclude that the reactivation of photosynthesis in blue‐green algae‐containing lichens is not prevented through high diffusion resistances for water.