Chain Correlation between Variables of Gas Exchange and Yield Potential in Different Winter Wheat Cultivars

Variables of gas exchange of flag leaves and grain yield potentials of five representative winter wheat (Triticum aestivum L.) cultivars varied greatly across different development stages under the same management and irrigation. The cultivars with high yield potential had higher net photosynthetic rate (P_N), PPFD (photosynthetic photon flux density) saturated photosynthetic rate (P_sat), stomatal conductance (g_s), and maximum apparent quantum yield of CO₂ fixation (_m,app) than those with low grain yield, but their dark respiration rate (R_D) and compensation irradiance (I_c) were remarkably lower. Compared with overall increase of yield potential of 71 % from low yield cultivars to high yield ones, P_N, P_sat, _m,app, and g_s were 13, 19, 57, and 32 % higher, respectively; but R_D and I_c decreased by 19 and 76 %, respectively. Such difference was evidently large during anthesis stage (e.g., P_N by 33 %), which indicated that this period could be the best for assisting further selection for better cultivars. However, transpiration rate (E) and water use efficiency (WUE) differed only little. At different development stages, especially at anthesis, P_N and P_sat were positively correlated with _m,app, g_s, and yield potential, and negatively correlated with R_D and I_c. Thus the high-yield-potential winter wheat cultivars possess many better characters in photosynthesis and associated parameters than the low-yield cultivars.