Photosynthetic Characteristics of a Super High Yield Cultivar of Winter Wheat During Late Growth Period

The mechanism of high yield of winter wheat in the field at late growth period was investigated by measuring the photosynthetic characteristics of photosystem II (PSII) and xanthophylls cycle, which could provide physiological reference for breeding. Weimai 8 (W8), a super high yield cultivar, and Lumai 14 (L14), a control cultivar were object. The photosynthetic rate (Pn), parameters of chlorophyll fluorescence and chlorophyll content were measured. The Pn, maximum photochemical efficiency of PSII (Fv/Fm), quantum yield of PSII electron transport (ΦPSII), efficiency of excitation energy capture by open PSII reaction centers (Fv′/Fm′), and photochemical quenching coefficient (qP) were higher in Weimai 8 compared to that in Lumai 14, a commercial high yield cultivar. Furthermore, Weimai 8 showed a lower nonphotochemical quenching coefficient and a lower de-epoxidized ratio of the xanthophyll cycle pigments than of Lumai 14 at late growth period. At mature stage, chlorophyll content of different leaves decreased both in Weimai 8 and Lumai 14. Chlorophyll content in flag, second and third leaf from the top of plant decreased more in Lumai 14 than in Weimai 8. These results suggested that Weimai 8 had more antenna pigments to absorb light energy, and had higher photosynthetic capability and photochemical efficiency of PSII. The yield of Weimai 8 was also higher than that of Lumai 14.