Abstract
In order to establish an adequate method of examining the inhibitory effect of SO2 on photosynthesis in rice, we examined the effect of SO2 under various conditions differing in growth stage, CO2 concentration, light intensity, leaf position, leaf age and others. The rate of recovery from the inhibition was also examined. When whole (individual) plants were exposed SO2 between 8 : 00 and 14 : 00, light intensity and CO2 concentration scarcely influenced the inhibitory effect of SO2 on photosynthesis and recovery rate from the inhibition. When only a leaf blade was exposed to SO2, the inhibitory effect was the highest in the latest expanded leaf blade. The photosynthesis-inhibiting effect of SO2 in the flag leaf was higher at the heading stage than at 10 or 20 days after heading. However, the most stable results were obtained when the flag leaf was exposed to SO2 10 days after heading irrespective of the cultivation method.
