Abstract: Photosynthetic properties were investigated in two newly-developed high-yield wheat (Triticum aesticum L.) varieties, Ningmai 8 and Ningmai 9, in order to elucidate both photosynthetic decline of flag leaf senescence, and variety differences. The results showed that, after anthesis, with increasing ear mass and specific leaf mass, there were decreases in relative water content, chlorophyll content, light-saturated net photosynthetic rate (P_nmax), light saturation point (LSP), apparent quantum yield (AQY), and electron transfer activities of PSI, PSII and whole electron transport chain, especially significant after yellow ripening, whereas ratio of chl a/b, light compensation point (LCP) and respiration rate (R_d) were gradually increased from anthesis to yellow ripening, and after that rose markedly. The findings here indicated that before yellow ripening, P_nmax decreased slowly with wider range of light availability, and after that P_nmax dropped quickly with less range of light availability. Compared with Ningmai 8, Ningmai 9 with higher yield showed earlier senescence in flag leaves.

Key words: wheat, flag leaf, senescence, photosynthetic light response curve, electron transport