Photosynthetic Characteristics During Grain Filling Stage of Summer Maize Hybrids with High Yield Potential of 15 000 kg·ha～(-1)

【Objective】A field trial was conducted to reveal the relationship between photosynthetic characteristics during grain filling stage and yield potential of summer maize hybrids with high yield potential of 15 000 kg·ha-1.【Method】Three summer maize hybrids(XY335,DH3632 and DH3806)were randomly planted at 78 000 plants/ha in the farmlands of Denghai Seed Co.Ltd in Laizhou city,Shandong province.Scientists measured above-ground biomass partitioning and photosynthetic characteristics of leaves on ear position to reveal the activities of photosynthesis and the bases of yield formation of three high-yielding maize hybrids during grain filling stage.The characters of grain filling were simulated by Richards' model.【Result】Yields of three hybrids were over 15 000 kg·ha-1,and the yield of XY335 was higher than that of DH3632 and DH3806 significantly(P0.05).Characterization of grain filling by Richards' model showed that XY335 performed the higher grain-filling rate,the longer duration of active growing period(50 d),and it reached the maximum grain-filling rate earlier than DH3632 and DH3806.The results indicated that the grain-filling characteristic like XY335 was favorable to 15 000 kg·ha-1 yield potential in the experiment.The photosynthetic parameters of XY335 were the highest among the three hybrids.Photosynthetic activities of XY335 ware optimal with higher PEPCase and RuBPCase activity and chlorophyll a/b ratio after anthesis.Soluble protein contents decreased slowly from 30 d and 50 d after flowering.Leaf area and net photosynthetic functional duration of XY335 were 60 d and 50 d,respectively.【Conclusion】 In order to develop hybrids with high yield potential of 15 000 kg·ha-1 and develop cultivation practices,it's essential to improve the photosynthetic activities to maintain higher grain-filling rate and longer duration of active growing period.This should be after anthesis under high density conditions to enhance the solar energy use efficiency.