A Leaf Layer Spectral Model for Estimating Protein Content of Wheat Grains 27 radiation balances are likely to occur if the internal variability of derived surface products,the typical distances that photons may travel horizontally within such 3-D media extend to spatial scales that are similar to or larger than those of the measuring sensor In order to maintain the energy balance of the overal forest domain,lacal canopy volumes with rather large positive net horizontal fluxes must also exist,thus underscoring the importance of properly locating local flux measurement equipment(Jean-Lu Widlo si.2006.Th ergy ed for measure the vertical and spatial distrib ution of ra r prct forest vertical using the resun showed the multi-angle spectral provided a relatively direct measure of vertical structure(D.S.Kimes 2006).The anisotropic scattering of both the vegetation canopy and the background is taken into consideration in a two-layer model of the bidirectional reflectance of homogeneous vegetation canopies(S.Liangrocapart,2002). In this study,two wheat varieties differing in plant- re studied using the leaf layer slice hod b anal ges for erent leaf layers at different The spectral characteristics varied in 300-700nm 800-1300 am and 1400-1800nm wave bands because of removal of leaf layers and differences in view angle.The change in the visible wave bands was less than that in near infrared wave bands and that in Jingdong&was less than that in Zhongyou9507. (2)Compared with the traditional 90 view angle,the spectral information of under leaves wer more at 30 and 60 than other view angles;for upper leaves the information at oo view angle.The ral in e of upp of Zho u9507a angle was that of Jingdong8. .The upper aves hxaeedwhe captured much radiation because of their horizontal orientation,the proportion of upward leaves was bigger than that of downwards leaves.In contrast,the radiation characteristics were complicated in the erect leaf plant-type. (3)The predicted GPC model by leaf layer spectra using 0 view angle were feasible.the RMSE was 0.7500 for Jingdong8 and 0.6461 for Zhongyou9507.The determinant coefficie nts Rbetween m red and estimated grain otein contents were0.7467and0.759 9.Thus,the leaf layer model would be relia for predicting grain protein content. In precision agriculture,it is important to accurately measure the state of a crop's growth using remote sensing techniques.In this study,we analyzed the canopy spectral characteristics of two wheat types and observed that canopy spectra were influenced by leaf layers and view angles;the spectral response of under leaves varied with different view angles.A quantitative study of different leaf layers and their spectra is needed for precise anag m en t Sinc sults were obtained only in Peking region,more experiments sho uld done in other regions Acknowledgments This work was ted with grants (2006AA10Z207.2006AA10A302)from the &D (30760109) the Nati andation of Chin and (2007BAHI2B02 National Kev Tschnolosy R&D Pro ona al ScienceA Leaf Layer Spectral Model for Estimating Protein Content of Wheat Grains 27 radiation balances are likely to occur if the internal variability of derived surface products, the typical distances that photons may travel horizontally within such 3-D media extend to spatial scales that are similar to or larger than those of the measuring sensor In order to maintain the energy balance of the overal forest domain, lacal canopy volumes with rather large positive net horizontal fluxes must also exist,thus underscoring the importance of properly locating local flux measurement equipment(Jean-Luc Widlowski, 2006). The more accurate modeling of energy are required for remotely measure the vertical and spatial distribution of forest structure. The potential of using a multi-angle spectral sensor to predict forest vertical structure were researched, the results showed the multi-angle spectral provided a relatively direct measure of vertical structure(D.S.Kimes 2006). The anisotropic scattering of both the vegetation canopy and the background is taken into consideration in a two-layer model of the bidirectional reflectance of homogeneous vegetation canopies(S.Liangrocapart, 2002). In this study, two wheat varieties differing in plant-type were studied using the leaf layer slice method by analyzing the spectral changes for different leaf layers at different view angles in the plane of vertical wheat line. We noted that: (1) The spectral characteristics varied in 300-700nm, 800-1300nm and 1400-1800nm wave bands because of removal of leaf layers and differences in view angle. The change in the visible wave bands was less than that in near infrared wave bands and that in Jingdong8 was less than that in Zhongyou9507. (2) Compared with the traditional 90° view angle, the spectral information of under leaves were more at 30 and 60° than other view angles; for upper leaves the information was more at 0° view angle. The spectral influence of upper leaves of Zhongyou9507 at 0° view angle was less than that of Jingdong8. The upper leaves of the lax-leafed wheat captured much radiation because of their horizontal orientation, the proportion of upward leaves was bigger than that of downwards leaves. In contrast, the radiation characteristics were complicated in the erect leaf plant-type. (3) The predicted GPC model by leaf layer spectra using 0° view angle were feasible, the RMSE was 0.7500 for Jingdong8 and 0.6461 for Zhongyou9507. The determinant coefficients, R2 between measured and estimated grain protein contents were 0.7467 and 0.7599. Thus, the leaf layer model would be reliable for predicting grain protein content. In precision agriculture, it is important to accurately measure the state of a crop’s growth using remote sensing techniques. In this study, we analyzed the canopy spectral characteristics of two wheat types and observed that canopy spectra were influenced by leaf layers and view angles; the spectral response of under leaves varied with different view angles. A quantitative study of different leaf layers and their spectra is needed for precise crop management. Since results were obtained only in Peking region, more experiments should done in other regions. Acknowledgments This work was supported with grants (2006AA10Z207, 2006AA10A302) from the National High Tech R&D Program and (30760109) from the National Natural Science Fundation of China and (2007BAH12B02) National Key Technology R&D Program