Evidence for Dark Repair of Far Ultraviolet Light Damage in the Blue‐green Alga, Gloeocapsa Alpicola

The inactivating effect of far UV light on the unicellular blue‐green alga Gloeocapsa alpicola could be totally reversed by exposure to blue light immediately after irradiation. However, if the irradiated cells were held in the dark before exposure to blue light, reversal became progressively less efficient and almost disappeared after 60–80 h holding. Caffeine and acriflavine inhibited loss of photoreversibility, suggesting an involvement of excision functions. Chloramphenicol and rifampicin slightly increased the rate of loss of photoreversibility, indicating that inducible functions play only a minor role. Split UV dose experiments indicated that light‐dependent repair remained operational during dark liquid holding. These results provide preliminary evidence for dark repair in G. alpicola .