Characteristics of Photosynthesis and Chlorophyll Fluorescence of Different Position Leaves at Booting Stage in Rice Genotypes with Different Leaf Colors

Four rice genotypes with different leaf colors were examined at booting stage for investigating the photosynthesis and chlorophyll fluorescence properties of different position leaves. The dark-green leaf rice genotype had the highest SPAD value, but not highest net photosynthetic rate(Pn), which suggested that the genotype with the highest chlorophyll content didn't mean the highest Pn. There were no significant differences in fluorescence parameters between dark-green leaf color and light leaf color genotypes.The Pn, stomatal conductance(Gs), transpiration rate(Evap) of the first leaf were significantly lower than that of the second leaf, while the intercellular CO2concentration(Ci) had little change, which indicated that the decrease of Pn did not result from the decrease of Gs. The decrease of SPAD value that has a close correlation with chlorophyll content was one of the apparent reasons resulted in decease of Pn. Further evidence from chlorophyll fluorescence showed that the Fo, Fm, Fv/Fm and PI changed with the leaf position but the Fm of the first leaf in the four genotypes was bigger than that of the second leaf, which showed that PSⅡelectron transport potential of the first leaf was stronger than that of the second leaf. The absorption per active reactions centers(ABS/RC), dissipation per active reaction centers(DIo/RC) and happing per active reaction centers(TRo/RC) in the first leaf were higher than those in the second leaf in three rice genotypes except Shennong07015, which showed that the remainder energy dissipation efficiency in per active reaction centers in the first leaf was higher than that of the second leaf.