Effects of SO2, O3, and SO2 and O3 in combination on photosynthesis and ultrastructure of two lichen species

Flavoparmelia caperata (L.) Hale and Umbilicaria mammulata (Ach.) Tuck, were exposed to 262 μg SO2 m−3, 59 μg O3 m−3, and 262 μg SO2 m−3 in combination with 59 μg O3 m−3 for 20 h over a 5-day period. Photosynthesis and ultrastructural observations were made after 12 and 20 h. At these low concentrations of pollutants, ultrastructural changes preceded and accompanied decreases in photosynthesis rates. Ozone was more phytotoxic than SO2. Ultrastructural damage was least with SO2 and greater and very similar with O3 and the combination of O3 and SO2. Photosynthetic data showed that SO2 ameliorates effects of O3. Electron micrographs showed increased accumulation of starch and cavity space around starch grains in the chloroplast and increased lipids in the cytoplasm in F. caperata; there was some increased starch in U. mammulata, but alterations were primarily in increased chloroplast opacity. Photosynthesis of U. mammulata was more sensitive to the pollutants than that of F. caperata. Ultrastructural damage was greater when samples were stored in the light than when they were stored in the dark between fumigations. The study shows that species vary in their responses to pollutants and that combinations of pollutants may give results different from those obtained with single pollutants.

Constancy of enzyme electrofocusing patterns in a stand of the lichen Umbilicaria mammulata

Thalli of the lichen Umbilicaria mammulata (Ach.) Tuck, were collected from one site, 24 at each of five different sampling times, over a period of 1 year. Protein extracts from each individual thallus were subjected to isoelectric focusing, followed by specific staining for eight enzyme systems (mannitol dehydrogenase, isocitrate dehydrogenase, 6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, glutamate dehydrogenase, superoxide dismutase, esterase, and alkaline phosphatase). A total of 55 bands were resolved, 25 of which were constant in all thalli through all sampling dates. Principal components analysis of the electromorph data showed the existence of groups corresponding to sets of thalli collected at the same times; esterase and alkaline phosphatase variation were primarily responsible for these groupings. Banding patterns of 6-phosphogluconate dehydrogenase and superoxide dismutase were constant regardless of date of collection. Most bands of glucose-6-phosphate dehydrogenase and glutamate dehydrogenase were consistent through all sampling times, but each system exhibited one band that differed in frequency from one collection date to another. Electromorphs of mannitol dehydrogenase and isocitrate dehydrogenase exhibited only minor variability. Dehydrogenase enzymes, since they tended to vary least from one sampling time to the next, can thus be used more readily for taxonomic purposes. If esterases and alkaline phosphatases are to be applied as taxonomic criteria, samples for comparison should be collected simultaneously.

Intraspecific variability of isozymes of the lichen Umbilicaria mammulata

Thalli of the lichen Umbilicaria mammulata (Ach.) Tuck, were collected from six geographically distinct locations and extracts of these were analyzed by isoelectric focusing to test for isozyme variability within and between sites. A total of 58 bands were resolved representing eight different enzyme systems; some enzymes exhibited mostly constant electromorphs, and the remainder were highly polymorphic with many variable bands. Other enzyme systems were not reliably detectable in U. mammulata. Sums of squares agglomeration and principal-components analysis of the molecular data showed the existence of distinct groups corresponding to sets of thalli collected at each of the collection sites. There was a positive correlation between the phenctie distance between sites, based on isozyme distribution, and physical intersite distance.