Changes in SPAD Value and Photosynthetic Rate during Grain Filling of Oryza glaberrima Strains and Oryza sativa Cultivars

Young Hwan YOON, Akihiro ISODA, Hiroshi NOJIMA and Yasuo TAKASAKI

Abstract : The process of the senescence in Oryza glaberrima Steud. strains and Oryza sativa L. cultivars were examined in terms of SPAD value(chlorophyll content) and photosynthetic rate. SPAD values and photosynthetic rates of flag leaves for 10 genotypes of each species was measured at the 1, 3 and 5 weeks after heading. SPAD values and photosynthetic rates of O. glaberrima strains tended to decrease rapidly after heading. O. sativa cultivars showed slower decrease as compared to O. glaberrima strains, in particular during the period from I to 3 weeks after heading. Although there was no significant difference between the two species in the mean value of photosynthetic rate and SPAD value at I weeks after heading, O. glaberrima had lower values after 3 weeks after heading. There were significant positive correlation coefficients between the photosynthetic rate and the SPAD value at I and 3 weeks after heading for O. glaberrima strains, and at 1 and 5 weeks after heading for O. sativa cultivars. There were significant positive correlations between the decreasing rates of the photosynthetic rates and the decreasing rates of the SPAD values at the period from the 1 to 3 weeks after heading for both species. At the period from 3 to 5 weeks after heading, only O. glaberrima showed a significant correlation between two traits, indicating that rapid decrease in chlorophyll content would affect the photosynthesis in O. glaberrima.

Key words : Oryza glaberrima Steud., Oryza sativa L., Photosynthesis, Senescence, SPAD value (chlorophyll content).