Parmelia tinctorum of epiphitic lichens were fumigated for 48 hr with sulfur dioxide (0.1-0.3 ppm) and nitrogen dioxide (0.06-0.88 ppm) singly and in combinations. The effects on chlorophyll content, catalase activity and peroxidase activity of the fumigated frond were compared with those of the control.
Catalase activity and chlorophyll content decreased markedly by the fumigation with SO
2, and increased by the fumigation with NO
2.
Peroxidase activity increased by the lower level of SO
2 (0.1-0.2 ppm), and decreased in the higher level of SO
2 (0.3 ppm), and decreased by NO
2.
In the case of lower concentrations of the SO
2 and NO
2 mixtures, the effects of one gas on the chlorophyll content and enzyme activity were counteracted in the presence of another gas.
In the higher concentrations of the mixtures, the effects of SO
2 on chlorophyll content and catalase activity were accelerated synergistically by NO
2 mixed with SO
2, and the effects of NO
2 on peroxidase activity were enhanced by SO
2 mixed with NO
2.
Visual symptoms of damage were observed at the higher level of SO
2 and NO
2. SO
2 and NO
2 caused bleaching or necrotic areas and pinkish spots on the thallus respectively.
Visual injury was enhanced by SO
2×NO
2, and the symptom was more analogous to that of SO
2 than NO
2.
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