Abstract
This experiment was undertaken to determine the effect of sulfur dioxide on the respiration rate at the flowering stage of rape plants. The respiration rate was measured in the laboratory under the controlled temperature of l0°C, 20°C and 30°C, respectively, exposing the plants to various concentrations of SO2, which were determined with a SO2-analyzer of self recording system. The results obtained were as follows: 1. The respiration rate at the flowering stage of rape plants was accelarated by exposing the plants to SO2 at the concentrations of 5, 10, 15 and 20 ppm under the condition of 30°C. At 20°C, the respiration rate was generally suppressed for five hours af ter exposing the plants to SO2, excepting SO2-20 ppm. At l0°C, it was depressed by the fumigation of sulfur dioxide, as seen in fig. 1, ftg. 2 and fig. 3. 2. In the relation between the concentration of sulfur dioxide and treatment hours by the gas, the respiration rate increased linearly with increasing concentration of SO2 under the condition of 30°C. At 20°C, it was supressed for 0∼4 hours after expoing the plant to SO2, but for 5∼8 hours, it was accelarated by the treatment of SO2 at the concentrations of 5 and l0 ppm, without SO2-20 ppm. At 10°C, it was always retarted by the treatment of SO2, as seen in ftg. 4, fig. 5 and fig. 6. 3. The mean Q10 values at the flowering stage of rape plants showed 1.60 and 1.65, by temperature ranging from l0°C to 20°C and from 20°C to 30°C, respectively. The mean Q10 value was higher in the plant treated by SO2 gas at the concentrations of 5, 10, 15 and 20 ppm, as seen in fig. 7 and table 1. From all these facts, it may be concluded that the respiration rate at the flowering stage of rape plants was affected by the concentration of sulfur dioxide, the treatment hours of SO2 and the different air-temperature.
