Author : Rungtavan Pushpavesa

Summary : Two varieties and seven new selections of rice were planted in 1971 dry season to determine how flag leaf characters and photosynthetic efficiency contribute to grain yield and dry matter production. Photosynthesis of attached flag leaves were measured at flowering stage by infrared gas analyzer using the leaf chamber. Angle, length, width, area and thickness of the flag leaves of the selections were measured. Grain yield was closely associated with and strongly dependent upon flag leaf width and leaf area index at flowering stage. There were indications that flag leaf angle and area are associated with grain yield, although the correlation coefficients were not significant. No association was observed between grain yield and leaf length, and grain yield and leaf thickness. Dry matter production was independent of all flag leaf characters. There were significant differences in photosynthetic rate among the selections. Photosynthetic rate and grain yield seemed uncorrelated, however, dry matter production tended to be inversely related to photosynthetic rate. Strong association between photosynthetic rate and leaf thickness was found, and the former was significantly influenced by the latter.