Degree Name

Master of Science (MS)

Semester of Degree Completion

1981

Thesis Director

Terry M. Weidner

Abstract

Extensive research regarding the effects of sulfur dioxide (SO2) on vascular and nonvascular plants has been reported. Sulfur dioxide has been shown to interrupt normal metabolism, to interrupt normal reproduction, and to alter the plant's morphology.

One hypothesis regarding the lack of bryophytes in urban areas is that the life cycle is being interrupted. It has been shown that moss protonemata are sensitive to SO2 concentrations in urban areas. Several authors noted that sexual reproduction is blocked among many species which do occur in urban environments. Observations on protonemal sensitivity are probably more important than the observations on the blockage of sexual reproduction since reproduction in mosses involves a protonemal stage.

Although mosses have not been studied as extensively as lichens, published research has shown that mosses are at least as sensitive to air pollutants as are lichens. Unfortunately, most studies of air pollutant effects on mosses have utilized unrealistic concentrations of SO2 as compared to those to be encountered in urban areas. In this study, some more realistic SO2 concentrations have been used.

The focus of this research was the investigation of the effects of SO2 on various ages and species of moss protonemata. The mosses used in this investigation were Aulacomnium heterostichum (Hedw.) B.S.G., Bartramia pomiformis Hedw., Leucobryum glaucum Agstr. ex Fr., and Polytrichum ohioense Ren. & Card. The protonemata of these mosses were fumigated under varying SO2 concentrations (0.2 ppm, 1.0 ppm, 5.0 ppm) in a flow-through chamber for eight hours. For each SO2 concentration, three different flowrates (1.0 liters per minute, 2.0 lpm, 4.0 lpm) were used. These flowrates and concentrations resulted in nine different fumigation treatments for each moss. In addition, the protonemata and resulting young gametophytes fumigated, were 2-rnonth, 4-month, and 8-month old cultures.

This research included using different flowrates through the fumigation chamber to allow a comparison of both flowrate effects and SO2 concentrations on chlorophyll destruction.

Chlorophyll analysis, after SO2 fumigation, revealed both a species and age differential response to chlorophyll destruction from SO2. Leucobryum glaucum was found to be the most SO2- sensitive and Bartramia pomiformis somewhat less. Aulacomnium heterostichum and Polytrichum ohioense were found to be more SO2-resistant. Age of the moss gametophyte was shown to be an important factor in SO2-resistance. As reported in the literature, gametophytes were more resistant as age increased.

In addition to the relationship between SO2 concentrations and chlorophyll destruction, there appears to be a correlation between atmospheric turnover in the fumigation chambers and chlorophyll destruction. Data, obtained in this research, indicate that an increase in the amount of SO2 brought in contact with the mosses brings about additional chlorophyll destruction. That is, destruction of chlorophyll is related both to SO2 concentration and to the amount of SO2 to which mosses are exposed. This is a variable that needs to be considered in any future research on SO2 effects on plants.

The four moss species investigated exhibit sufficient SO2 sensitivity in the young gametophyte stages so that their life cycle could be easily interrupted by moderate levels of SO2 pollution. This could lead to an eventual extinction of these species in an area polluted by SO2.

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