Research And Application Of The Optimal Stomatal Regulation Mechanism Based On The Crop Efficient Water Use At Leaf Scale

For efficient,accurate regulation of crop transpiration,typical C3 crops(soybean and grape)and C4 crop(maize)in the northwestern arid area were studied in this paper.Field experiments and model simulations were used to study the optimal stomatal regulation mechanism based on the crop efficient water use at leaf scale.The two experiments:the relationship of stomatal conductance-photosynthesis-transpiration in the field and the effect of new anti-transpirant FZ on soybean were carried out at Shiyanghe Experimental Station for Water-saving in Agriculture and Ecology of China Agricultural University in Gansu Province of Northwest China.The relationships between transpiration rate,photosynthetic rate and stomatal conductance were analyzed,and the occurrence condition of luxury transpiration were discussed.The optimal stomatal conductance model(OSR)was modified under water-stressed condition based on the linear relationship between the marginal water consumption of carbon assimilation and the soil water content,as OSRM1 and OSRM2 model.The three optimal stomatal conductance models and two traditional stomatal conductance models Jarvis and Ball-Berry-Leuning(BBL)were used to simulate the stomatal conductance of soybean,grape and maize from 2012 to 2015.The optimal stomatal conductance-photosynthesis-transpiration model(OSRJ)based on environmental factors was derived,and the regulating intervals of luxury transpiration were quantified under different environmental conditions by this model.In order to guide the practical production,the regulation effect of new anti-transpirant FZ was explored on soybean in an arid area.The main results are as follows:(1)The diurnal variation of stomatal conductance,photosynthetic rate and transpiration rate of soybean,grape and maize leaves were similar under different soil water content and radiation conditions.Under the high soil water content condition,the diurnal variation of stomatal conductance,photosynthetic rate and transpiration rate were synchronized and all single-peak curves.And the peaks were at the strongest radiation stage.During the stable radiation stage,the stomatal oscillation occurred,and the oscillation frequency was at 7?16 min.Under the low soil water content condition,the diurnal variation of stomatal conductance,photosynthetic rate and transpiration rate of soybean and grape leaves were not synchronized,and no stomatal oscillation occurred.(2)The regulation of luxury transpiration was clarified,and the existence of crops luxury transpiration was closely related to soil water content and photosynthetically active radiation.The luxury transpiration appeared only under the high both soil water content and photosynthetically active radiation.Under the high soil water content condition,the luxury transpiration appeared during 9:00?15:00 in the typical sunny day.(3)And the estimation accuracy of leaf stomatal conductance on soybean,grape and maize by the optimal stomatal conductance models(OSR,OSRM1,OSRM2)were improved compared with Jarvis model and BBL model.The OSRM1 and OSRM2 models performed more stable on simulationg the stomatal conductance of soybean,grape and maize in different years compared with Jarvis model and BBL model.Compared with OSR model,the accuracy of Jarvis model and BBL model was increased by 8%,37%and 56%respectively.The diurnal variation of stomatal conductance of soybean,grape and maize leaves was the highest,and the OSRM1 and OSRM2 models were most accurate.(4)The optimal stomatal conductance-photosynthesis-evapotranspiration model(OSRJ)based on environmental factors was established to quantify the regulating intervals of stomatal conductance of soybean and grape leaves under different environmental conditions.Under severe water deficit condition,for both soybean and grape,leaf stomatal conductance during the day had been basically in the optimal state.Under moderate water deficit condition,the luxury transpiration generally appeared during the 11:00-14:00.Under sufficient water deficit condition,luxury transpiration appeared during 9:00-17:00.If the stomatal conductance of soybean leaves in the whole day is reduced by 23.4%by applying the exogenous hormones,the transpiration rate will decrease by 19.1%,the photosynthetic rate will decrease by 0.9%,and WUEi increased by 41.5%.(5)The effect of spraying FZ on soybean under different irrigation rates was evaluated.Under the low irrigation rate,leaf stomatal conductance(gs)and transpiration rate(Tr)decreased significantly by 7 d after spraying,but the photosynthesis(Pn)and instantaneous water use efficiency(WUEin)were not significantly affected.Applying FZ three times during pod bearing and pod filling stages did not significantly affect the final biomass,water consumption,seed yield and WUE of soybean.Under the local irrigation rate,applying FZ increased the activities of superoxide dismutase and peroxidase in the leaves by 38%and 33%,respectively,but did not significantly affect gs,Tr,Pn,stomatal aperture and stomatal frequency.Applying FZ three times during pod bearing and pod filling stages enhanced seed yield and WUE by 24%and 21%,respectively.