Chain correlation between variables of gas exchange and yield potential indifferent winter wheat cultivars

Variables of gas exchange of flag leaves and grain yield potentials of five representative winter wheat (Triticum aestivum L.) cultivars varied greatl y across different development stages under the same management and irrigat ion. The cultivars with high yield potential had higher net photosynthetic rate (P-N), PPFD (photosynthetic photon flux density) saturated photosynthe tic rate (P-sat), stomatal conductance (g(s)), and maximum apparent quantum yield of CO2 fixation (Phi (m,app)) than those with low grain yield, but t heir dark respiration rate (RD) and compensation irradiance (I-c) were rema rkably lower. Compared with overall increase of yield potential of 71% from low yield cultivars to high yield ones, PN, Psat, Phi (m,app), and g(s) we re 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 anthe sis stage (e.g., PN by 33 %), which indicated that this period could be the best for assisting further selection for better cultivars. However, transp iration rate (E) and water use efficiency (WUE) differed only little. At di fferent development stages, especially at anthesis, P-N and P-sat were posi tively correlated with Phi (m,app), g(s) and yield potential, and negativel y correlated with R-D and I-c. Thus the high-yield-potential winter wheat c ultivars possess many better characters in photosynthesis and associated pa rameters than the low-yield cultivars.