| In recent years,with the global climate warmed up gradually,southern region of China especially in the middle and lower reaches of the Yangtze river valley's paddy rice production area presented high temperature frequently in summer,which inevitablely have certain influence on the rice production.Therefore,a dynamic high-temperature monitoring,early warning,assessment and defense become the emphasis of rice heat damage study.Since remote sensing data could be acquired from different sensors and has non-destructive to crop,which makes disaster assessment possible,and there has been an increasing amount of international interest in rice monitoring.In this study,the data were obtained in different places of Jiangsu province in 2007 and 2008.Setting different temperature gradient and stress in the key growth stages of rice to simulate the growth of rice high-temperature environment to study the response of physiological and canopy hyperspectral characteristics of rice under high temperature stress,and the reverse mechanism of rice to avoid the stress was investigated.A radiative transfer simulation,linking leaf and canopy models was conducted and named PROSAIL model in this study,the feasibility and sensitivity analysis of PROSAIL model were carried on in the meantime.In this coupled model, input a large number of different values of some key parameters to simulate MODIS canopy reflectance,and then obtained statistical models between canopy water content(EWT,Equivalent water thickness) and spectral index(SRWI,Simple ratio water index),combined the model of EWT and canopy temperature,established the model of canopy temperature and SRWI.Canopy temperature in Jiangsu province at booting and heading stages was estimated using the statistical model and MODIS data. The main conclusions are as follows:1) The MDA(Malonaldehyde)content,as well as the osmolyte content and endogenous antioxidants and antioxidant system have no obvious change under 35℃ high temperature stress ld and 3d,and 39℃high temperature stress 1d,which may be the critical temperature and time of rice high temperature injury.With the deepening of coercion,lipid peroxidation exacerbated,MDA content and electrolyte penetration increased dramatically,while the content of osmotic adjustment substance,such as proline,soluble sugar and soluble protein decreased.Meanwhile,high temperature stress led to SOD(Super oxide dismutase) activity and the content of antioxidants such as AsA(Ascorbic acid) and Glutathione(GSH) decrease greatly.In addition,high temperature stress led to rice pollen viability and germination rate,seed-setting rate has dropped drastically.High temperature stress had damaged the membrane structure of rice cell,which inevitablely affected the physiological activities.Other things be equal,the response amplitude of the above mentioned physiological parameters of Yangdao 6 are obvious than Nanjing 43.The tolerance ability under high temperature stress of Nanjing 43 are higher than that of Yangdao 6.2) Rice canopy reflectances have different spectral response under different growth stages and temperature stress.Near-infrared reflectance,as well as the red edge parameters,reached their peak values at booting stage,and decreased with the deepening of the degree of temperature stress.Under the same condition,the difference of spectral reflectance among the same observation date of distinctive high temperature stress treatment are more obvious than Nanjing 43.3) A model simulation is conducted with the real parameters of Yangdao 6 of different development stages and the PROSAIL model,the results shows that:analog value and the measured R~2 values greater than 0.97,RMSE less than 0.05,which demonstrating that the radiative transfer model could be used for simulating spectrum of rice canopy.Combing the simulation of SRWI and EWT with the statistical model of temperature and EWT,The applicability of radiative transfer model inversion methods to MODIS is carried on,investigating its capability for canopy temperature retrieving.
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