Interspecific Differences in Responses of Transpiration to SO2

The effect of SO2 on transpiration of various plant species was tested. The pattern of changes in transpiration rate during the course of SO2 fumigation was significantly different between plant species. Fumigation with 2.0 ppm SO2 induced the rapid decline of transpiration rate of rice and tomato. In other plant species, the transpiration gradually decreased with or without initial increase. Those plant species with rapid decline of transpiration rate were generally more tolerant to SO2 than the species with gradual decrease of transpiration rate. However, this speculation is not always true. For ginkgo plant, the increase in transpiration rate was observed for about 3 hours with no visible injury.