SUMMARYIn two open, flow-through systems 11 lichen species were fumigated with concentrations between 0-036 and 2-0 ppm {c. 94-3-5240//^g m~^) SOg. Sulphur dioxide uptake was monitored concurrently as a mass balance between incoming and outgoing SOg concentrations. The rate of uptake ranged from 0-025 (±0-006) to 0-7 (±0-16) nmol SO^ g"^ d. wt s~\ for all species. After the first hour of fumigation the uptake rate was almost constant during the following 5 h for concentrations up to 1-0 ppm SOg. At higher concentrations the uptake declined over time continuously. Within the range of measured SOg concentrations the uptake rate was linearly correlated with SO^ concentrations (r^ = 0-90). Thalli which were killed by heat treatment or in which respiration was inhibited by azide treatment did not show significantly different SOg uptake from living thalli. No differences in uptake were found during fumigation in the light versus in the dark.
Comparisons of whole-lichen physiology to the respective photobionts have often been unclear due to inherent differences in isolated photobiont culturing techniques. The use of 13-mm-diameter cellulose-acetate discs allows photobiont cultures access to nutrient agar medium, while improving ease of manipulation and distinct separation from the agar. Adequate culture growth for experimentation is reached in approximately three weeks, a time comparable to standard nutrient agar and liquid cultures. These discs are then available for use in a variety of manipulative techniques. Chlorophyll determination of an entire algal disc culture is obtainable because the discs readily dissolve in dimethylsulphoxide (DMSO), with no interference in the 400–700 nm range. Photosynthesis and respiration may be measured with standard gas exchange equipment. Photobiont discs allow for fumigation in the gas phase with no increase in external ⊂pH reported to occur during gaseous fumigations in liquid media. The disc system is also useful for fluorescence studies. Trebouxia erici cultures exhibited a CO⊂2 gas exchange on a gram dry weight basis similar to whole lichen systems. The ease with which photobionts can be cultured and manipulated using this system allows for expanded experimentation and comparisons.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.