Abstract

During three rice generations in Asominori (Japonica) and IR24 (Indica), the yield and its components — namely grain yield per plant, fertile tillers, 1000-grain weight, grain number per panicle — were greater under Free Air CO₂ Enrichment (FACE,200 µmol CO₂ · mol^-1 above current levels) than those under current CO₂concentration (Ambient, about 370 µmol CO₂ · mol^-1). And significant difference in generations, varieties, and CO₂ concentrations existed in the yield and its components of Asominori and IR24. For the third generation planted under FACE, the dry matter weight of a single main stem and its components in Asominori and IR24 were higher under FACE than those under Ambient from the date of anthesis to maturation. As compared with that under Ambient, dry weight per day, filling power and remobilized C reserve under FACE increased in Asominori and IR24, but the transfer ratio of assimilate and harvest index (HI) declined under FACE. The degree of response to FACE in Asominori and IR24 showed that a positive response to long term treatment of elevated CO₂.

Key words: CO₂ concentration, Indica rice, Japonica rice, yield, yield components.