THE UPTAKE OF GASEOUS SULFUR-DIOXIDE BY NONGELATINOUS LICHENS

In two open, flow-through systems 11 lichen species were fumigated wit h concentrations between 0.036 and 2.0 ppm (c. 94.3-5240 mu g m(-3)) S O2. Sulphur dioxide uptake was monitored concurrently as a mass balanc e between incoming and outgoing SO, concentrations. The rate of uptake ranged from 0.025 (+/-0.006) to 0.7 (+/-0.16) nmol SO2 g(-1) d. wt s( -1), for all species. After the first hour of fumigation the uptake ra te was almost constant during the following 5 h for concentrations up to 1.0 ppm SO2. At higher concentrations the uptake declined over time continuously. Within the range of measured SO2 concentrations the upt ake rate was linearly correlated with SO2 concentrations (r(2) = 0.90) . Thalli which were killed by heat treatment or in which respiration w as inhibited by azide treatment did not show significantly different S O2 uptake from living thalli. No differences in uptake were found duri ng fumigation in the light versus in the dark.