ADAPTATION OF GRASSES TO LONG-TERM SULFUR-DIOXIDE POLLUTION

To study the adaptation of grass species to long-term SO2 pollution, seeds of Poa pratensis L., Dactylis glomerata L., Holcus lanatus L., and Arrhenatherum elatius (L.) P. Beauv. were collected from four sites in Germany differing in their SO2 pollution climate. Plants were grown from these seeds and exposed to SO2 at 0.25, 47.2, and 85.8 nl 1(-1) in open-top chambers (OTC) for 11 or 14 weeks. Growth (height, number of tillers, shoot and root biomass), stomatal conductance, leaf sulphur content, and compounds of the antioxidative system (non-specific peroxidases and glutathione) were determined. Controlled exposure to SO2 in OTC did not lead to any visible injury, however, growth was affected in some of the populations. Where there were effects, populations from polluted sites showed increased growth and those from less polluted sites showed decreased growth. Stomatal conductance was not affected in any of the populations by SO2. Leaf sulphur content was significantly raised by SO2 fumigation, however, no clear correlation between seed origin and sulphur content was found. A more pronounced increase in peroxidase activity was found in response to SO2 in populations from less polluted sites, suggesting that populations from polluted sites were more tolerant to SO2. Clear differences between populations were also detectable with respect to glutathione levels which were higher in populations from polluted sites when no SO2 was added in OTC. However, at higher SO2 fumigation levels, populations from all sites had comparable levels of glutathione.