Abstract
The effects of sulfur dioxide on photosynthetic rate at the flag leaf of rice plants at 10 days after the heading stage were studied with various cultivar. Sulfur dioxide was supplied at the rate of 2.6mg SO2 m-3 (about 1.0μL L-1) for 15 min and then was displaced with clean air for 1 hr. The inhibitory rate of photosynthesis widely ranged from 30.1% to 65.3% in 1998 and from 42.8% to 65.9% in 1999, showing a significant cultivar difference. The photosynthesis–inhibiting effects of SO2 in old four varieties (cv. Aikoku, Kamenoo, Kyotoasahi and Takenari) was significantly higher than that in new 10 varieties (cv. Akitakomati, Akibare, Akihikari, Koshihikari, Sasanishiki, Hatsuboshi, Nipponbare, Nourin 29 and Yamahikari). However, the effects of SO2 on the green index in leaf (SPAD value) was not significantly different between old and new cultivars.
