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Low-light recovery effects on assessment of photoinhibition with chlorophyll fluorescence in lichens

Abstract Chlorophyll a fluorescence is often used to estimate various types of damage in lichens. In order to optimize the output and improve interpretations of such measurements the protocol for pretreatment and measuring is important. To study the effects of measurement conditions, the lichens Lobaria pulmonaria, L. scrobiculata, Xanthoria parietina and Parmelia sulcata were first stressed by high light intensities at 600 or 1000 µmol photons m−2 s−1 for 4 h. Then various conditions during recovery or pretreatment were used to optimize the detection of more lasting damage. Recovery from photoinhibition was incomplete in darkness, whereas light as low as 0·2 or 1·0 µmol m−2 s−1 resulted in complete recovery if the recovery period was long enough. Additionally, low intensity light given for1·5 h after one day in darkness caused rapid and complete recovery. In conclusion, before measuring maximal PSII efficiency (F v/F m) with chlorophyll fluorescence, it is important to let lichens recover in low intensity light and not in darkness, to optimize recovery from photoinhibition; dark adaptation can only be recommended if the photoinhibition status of the lichens is of interest.