LAUSR

Th e vitality of 64 lichen species (107 individual lichen thalli) growing under diff erent light climates in an Araucaria forest in South Brazil was analyzed by chlorophyll fl uorescence. Study sites were grouped according to their local light availability under full sunlight (about 2200 μmol m-2 s-1): 1 = low light, up to 20 μmol m-2 s-1; 2 = medium light, 20 to 100 μmol m-2 s-1; and 3 = high light, more than 100 μmol m-2 s-1. Maximum quantum yield of photosystem II, as shown by Fv/Fm of dark-adapted samples, was mainly between 0.3 and 0.7, with extremes of below 0.1 and up to 0.85. On average, yields were highest with low light availability (0.66). Groups 1 and 2 were not signifi cantly diff erent from each other, but groups 1 and 3, as well as groups 2 and 3 were. After dark adaptation, lichens were exposed to diff erent light intensities by means of a chlorophyll fl uorometer. Th e results show that low light-adapted lichens exhibit the highest sensitivity to excess light, as was also indicated by the data for non-photochemical quenching. Th us, shade-adapted lichens are obviously well protected from possible damage caused by excess light, which is important when exposed to sun fl ecks.