用反射率、透射率和吸收率分析玉米叶片水分含量时的峰值波长选择

通过测定田间试验条件下11个玉米品种、3个氮肥处理、2个密度处理和4个生育期的100张叶片的反射、透射和吸收光谱(350～2500 nm)，发现玉米叶片在近红外和短波红外的水分吸收区域的反射/透射/吸收的中心峰值波长实际发生在974 nm、1160 nm和1440 nm，在这3个峰值波长，叶片反射率、吸收率与叶片水分含量之间的相关性好于透射率。在这3个峰值波长中，反射率、透射率和吸收率相互之间的关系以1440 nm为最紧密，在此波长光谱与叶片水分含量之间的相关性也相对较强。因此，1440 nm是用叶片反射率和吸收率反演植物的水分状况的最佳峰值波长。

Selection of the wavelengths of peak values in analyzing leaf water status by using leaf reflectance, transmittance and absorptance in corn plants

A field experiment consisting of eleven corn cultivars, three nitrogen level treatments and two population treatments to investigate the relationships among the leaf water content to leaf reflectance, transmittance and absorptance in different spectral regions of water absorption. One hundred leaves from four growth stages were analyzed. It was observed that the central wavelengths of peak values of leaf reflectance, transmittance and absorptance were at 974 nm, 1160 nm and 1440 nm in the water absorption regions. The leaf reflectance and absorptance at 974 nm, 1160 nm and 1440 nm were better related to the leaf water content than the leaf transmittance.The relationships among the leaf reflectance, transmittance and absorptance tended to be stronger at 1440 nm than that at 974 nm or at 1160 nm, and the leaf reflectance, transmittance and absorptance appeared to be slightly better related to the leaf water content than that at 974 nm or at 1160 nm. The results indicated that 1440 nm was the best wavelength of peak values in analyzing plant water status by using reflectance and absorptance.