Based On The Canopy Photosynthetic Active Radiation To Research Cotton Water Stress Condition Of Hyperspectral Monitoring

Object:Analysis of correlationship between canopy spectra and absorption photosynthetic active radiation(APAR),photosynthetic active radiation intercepted quantity(FAPAR,)and leaf net photosynthetic rate(Pn)of cotton Xinluzao 45 and Xinluzao 62 under different water treatments.Establishing spectrum and APAR,FAPAR,Pn model and screening sensitive wave band,and FAPAR and Pn can be derived by vegetation indice,for fast,large area monitoring the growth of cotton and water conditions,provide theoretical basis for the application of hyperspectral.Methods:Canopy hyperspectral reflectance data,photosynthetically active radiation(PAR)and leaf net photosynthetic rate of cotton Xinluzao 45 and Xinluzao 62 with different irrigation treatments were recorded in a field experiment by the ASD Fieldspec Pro FR 2500 spectroradiometer,LI-190 SA linear quantum sensor and LI-6400 portable photosynthesis system at cotton key growth stages.Results:Studies have shown that cotton Xinluzao 45 and Xinluzao 62 in the diurnal variation of the canopy,middle APAR trend similar in four stage to that of a bimodal curve,the change trend of the lower,parabolic.The diurnal variation of the cotton canopy,middle FAPAR performance first decrease and then increase trend,at 14:00 appear the lowest of the day,the change trend of the lower,and the change tendency of the canopy,middle is just the opposite.Two varieties of cotton APAR,FAPAR are all in flowering and boll-forming stage reached the highest value in life,their minimum values at the boll opening period.The changing trends of Pn is consistent with APAR,FAPAR in growth stage,but the Pn in the boll period reached the highest value in life.Establish function model of heavy normalized difference vegetation index(RDVI),difference vegetation index(DVI),enhanced vegetation index(EVI),photochemical reflection vegetation index(PRI)and FAPAR,Pn,reached extremely significant correlation.EVI of Xinluzao 45 and RDVI of Xinluzao 62 exponential correlation are best(rEVI-FAPAR =0.8749**,RMSE=0.07949,rRDVI-FAPAR =0.8098**,RMSE=0.03060,n=24),DVI of Xinluzao 45 and EVI of Xinluzao 62 are best correlation with the exponential function of the Pn(rDVI-Pn=0.6705**,RMSE=0.1711,r EVIPn=0.7985**,RMSE=0.2306,n=24).Multivariate statistical analysis showed that cotton canopy spectral reflectance and FAPAR in350-412,592-693 nm wavelength range significantly negative correlation,in 736-1151 nm band was significantly positively correlated,using 660 nm and 758 nm make up the normalized difference vegetation index(NDVI)and the ratio vegetation index(RVI)to establish a model of power function relationship between FAPAR,the correlation between RVI and FAPAR(r=0.7719**,RMSE=0.06661,n=40)is higher than the correlation between NDVI and FAPAR(r=0.7508**,RMSE=0.5861,n=40).Cotton canopy spectral reflectance and Pn in 350-708 nm wavelength range significantly negative correlation,in 737-1145 nm wavelength range wassignificantly positively correlated,674 nm and 806 nm for sensitive wave band,making up NDVI,RVI to establish a model of power function relationship between Pn,the correlation between NDVI(r=0.6688**,RMSE=0.04867,n=40)and Pn was higher than the correlation between RVI and Pn(r=0.6955**,RMSE=2.5631,n=40).Conclusion:Through correlation analysis and multivariate statistical analysis showed that the correlation between vegetation index,spectral reflectance and FAPAR significantly higher than the correlation of Pn.It showed that photosynthetic parameters information could be nondestructive acquisition by using hyperspectral data,in order to real-time monitor the cotton growth.