Studies On Photosynthetic Physiological Characteristics And Stomatal Conductance Simulation Of Maize In Semi-arid Area Of Longzhong

Maize is one of the main grain crops in the semi-arid area of Longzhong,which plays an important role in the native national economy.It is of great significance to study the maize photosynthetic physiological characteristics and its response to environmental factors for improving crop yield and building water-saving agriculture.Based on the data of the maize photosynthesis and physiological characteristics,soil moisture and meteorology from the field observation station in the semi-arid area of Huining,Gansu Province,the paper analyzed the photosynthetic physiological characteristics of maize leaves in the semi-arid area of Longzhong,including the light response,CO₂ response and diurnal variation process,and had studied the influence of soil moisture content on the photosynthetic physiological characteristics of maize.The photosynthetic light response model and CO₂ response model of maize leaves as well as stomatal conductance model had been carried on the data analysis and model evaluation in this paper.The main conclusions were as follows:?1?The Ye model was the best model for fitting the photosynthetic light response curve of maize leaves when the relative soil moisture content was 0.92 and 0.25,followed by the non-rectanglar hyperbolic model,the rectanglar hyperbolic model and exponential equation model had the worst simulation effects.When the relative soil moisture content was 0.92,the non-rectangular hyperbolic model was the best model to fit the photosynthetic CO₂ response curve of maize leaves;and the Ye model had the best fitting effect when the relative soil moisture content was 0.25.?2?In the precess of light respons,there was a positive correlation among the stomatal conductance,transpiration rate and net photosynthetic rate of maize leaves,while the intercellular CO₂ concentration was negatively correlated with the three.In the CO₂ response process,the stomatal conductance and transpiration rate were positively correlated,and the net photosynthetic rate was negatively correlated with both.The diurnal variation curves of stomatal conductance of maize leaves under the two soil moisture conditions were bimodal,reaching the peak at 12:00 and 15:00separately.When the relative soil moisture content was 0.92,the diurnal variation of net photosynthetic rate showed the unimodal curve,and the peak value appeared at12:00;when the relative soil moisture content was 0.25,the diurnal variation curve of net photosynthetic rate was bimodal curve,and the peak value appeared at 12:00 and15:00 respectively.The diurnal variation curve of intercellular CO₂ concentration was similar under the two soil water conditions,the density was higher in the morning and evening,and the lowest in the noon.The diurnal variation curve of transpiration rate of maize leaves showed bimodal curve under two soil moisture conditions,and the peak value appeared at 12:00 and 15:00.?3?Under low light intensity,photosynthetic physiological characteristics of maize leaves were nearly not affected by soil moisture;Under the high light intensity,the net photosynthetic rate,stomatal conductance and transpiration rate of maize leaves were positively correlated with relative soil moisture content,and the maize intercellular CO₂concentration was less affected by soil moisture.The stomatal conductance of maize leaves was more sensitive to the change of soil moisture,especially under water stress,along with the decrease of the soil moisture content,the decrease of stomatal conductance of maize leaves will accelerate.?4?During the observation period,the stomatal conductance was greatly affected by soil moisture content.The Ball-Berry-Leuning model?BBL model?was the best simulation effect on the stomatal conductance,followed by the optimal stomatal model?OS model?and Ball-Berry model?BB model?,and the simulation effect of three Jarvis models was poor,among which the simulationg effect of Jarvis3 model was the worst.After introduction of the soil moisture response function,the simulation effect of jarvis2 model becomes worse,and the simulation effect of the other five models was improved in varying degrees;the simulation effect of OS-?model who was modified by soil moisture response function is the best,followed by BBL-?model and BB-?model,jarvis1-?model and jarvis3-?model were poor,and jarvis2-?model has the worst simulation effect.?5?According to comparing the regression curve of stomatal conductance simulation value to relative soil moisture and the confidence interval range of observation value,the paper had determined the applicable soil moisture range of stomatal conductance model.Jarvis3 model,BB model,BB-?model,BBL-?model,OS model and OS-?model were all applicable in the relative soil moisture range of the observation period.It was applicable to the Jarvis1 model when REW<0.72,the Jarvis1-?model was suitable for the condition when REW>0.3,the Jarvis2 model was suitable for the condition when REW>0.22,the Jarvis2-?model was suitable for the condition when 0.27<REW<0.78,and the Jarvis3-?model was for REW>0.3.This study can provide a theoretical basis for promoting the scientific planting of maize and improving the utilization strategy of agricultural water resources in semi-arid area of Longzhong.