Studies On Photosynthetic And Nutrient Physiological Characteristics Of Super-high Yield Summer Maize Hybrids

Erectophile plant type maize hybrids play an important role in crop production in Huanghuaihai region in China nowadays.Three plant type maize hybrids with different compact degree were studied on photosynthetic and nutrient physiological characteristics in the experiment in order to provide basic information for production.Dry matter production and portioning, course of grain filling traits,leaf area index(LAI),gas exchange parameters (including P_n-net photosynthesis rate,Gs-stomatal conductance, C_i-intercellular CO₂ concentration),photosynthetic parameters(including pigment concentration,soluble protein content,RuBPCase and PEPCase activities) were determined to evaluate the photosynthesis performances and mass mineral elements such as nitrogen(N),phosphorus(P) and potassium(K) were determined to estimate the nutrition traits.Three summer maize hybrids(XY335,DH3632 and DH3806) were planted at 78000 plants ha^-1 in National Com Project Technology Research Center(Shandong).Yields of three-type maize hybrids were over 15000 kg ha^-1,and yield of XY335 was higher than that of DH3632 and DH3806 significantly(P＜0.05).Characteristic of grain filling analyzed by Richards equation showed XY335 had the higher grain-filling rate,the longer active growing period,and it reached the maximum grain-filling rate earlier than DH3632 and DH3806.The result indicated grain-filling traits like XY335 was favorable to high yield in the experiment.The leaves' photosynthetic physiology quantity of XY335 was highest of the three-type hybrids.XY335 had high net photosynthetic rate(Pn),PEPCase activity RuBPCase activity and chlorophyll a/b value after anthesis,and the leaf area index(LAI) and soluble protein content decreased slowly from 20d and 30d after flowering, respectively.To obtain 15000 kg ha^-1 of super high-yielding breeding and cultivation in practice,we need to improve the leaves photosynthetic physiology quantity to maintain high grain-filling rate and long active duration after anthesis enhance the solar energy use efficiency.The population density and individual physiological function are the two aspects to obtain super-high yield for summer corn,however,in our findings,it is more important to improve the photosynthetic and nutrient capabilities of individual plant at large population density.The N(P and K) harvest indexes of XY335,DH3632 and DH3806 were higher than other normal corn in practices which was the main reasons to get high grain yield for the three hybrids in the experiment.At maturity, absorption amount of N,P and K of XY335 was maximum,456.48 kg/ha, 150.63 kg/ha and 204.62 kg/ha.The uptake amount of N,P and K of DH3806 was minimum,371.29 kg/ha,127.12 kg/ha,199.90 kg/ha,respectively.The results indicated that higher N,K inputs were necessary to gain super-high yield in maize production.