Spatiotemporal Dynamic Research For Summer Corn Canopy's Photosynthetic-physiological Characteristics

It is an important research aspect of modern agriculture to improve the efficiency of plant light,and its core content is the efficiency of the plant's light energy.This paper is based on summer corn as the research object,and the photosynthetic characteristics of summer corn were discussed from several aspects,providing theoretical basis for improving the efficiency of summer maize photosynthetic and data support.The main research content and results of the paper are as follows:In order to have a better option for photosynthetic model,rectangular hyperbola,non-rectangular hyperbola,exponential function and Ye Zi-piao model were used to make photosynthetic light response curve fitting with the measured data of huge bellbottom period upper leaf,ear leaf,the lower leaf and the period of cupping,the mouth of the trumpet,and the period of maturity in two years.The fitting curve of each model and the reflection of the measured data were compared,and fitting residual errors of each model in three photosynthetic effective radiation segments were analyzed.The results showed that,the fitting result of Ye Zi-piao model is optimal,whether it is the fitting curve or the photosynthetic characteristic parameter.The fitting values for the maximum net photosynthetic rate of the rectangular hyperbola and the non-orthogonal hyperbolic model were much larger than the measured value,and the deviation increased with the plant's photosynthetic intensity,but the fitting results of satuation light intensity were far less than the measured value.Using Ye Zi-piao model to do photosynthetic-light response curves for summer corn,the photosynthetic response curve and the photosynthetic characteristic parameters of various fertility periods were obtained.According to net photosynthetic rate,the photosynthesis-light response curves of corns could be divided into 3 stages: the rapid growth phase,the weak growth phase and stationary phase,but the location of inflection points were different for each growth stage and different leaf positions.The leaf age has a great influence on photosynthetic characteristics during the whole growth period of corns.At the elongation stage of corns,photosynthetic rate and dark respiration rate increase gradually with the development of stem and leaf,which achieved the maximum values at the bell stage as the corns transform into physiological growth and the development of stem and leaf are stopped,and then its substantial decline for leaves senescence at the milk stage and full ripening stage.Moreover,the key photosynthetic parameters such as apparent quantum yield,photosynthetic rate and dark respiration rate at the upper leaves are larger than those at the bottom in the same growth period.The mechanism of stomatal conductance model and coupling mode that were put forward by Ye Zi-piao had been verified by measured data of summer maize in jointing stage multiple and milk-ripe stage.According to the analysis of the response curve of net photosynthetic rate-stomatal conductance,photosynthetic active radiation-net photosynthetic rate and photosynthetic active radiation-stomatal conductance,We concluded that the stomatal conductance in jointing stage is bigger than milk-ripe stage?s,summer maize jointing stage blades of net photosynthetic rate and stomatal conductance were positively correlated,but stomatal conductance and net photosynthetic rate didn?t synchronize with the change of photosynthetic active radiation.