玉米叶片高光谱反射率、吸收率与色素含量的关系比较分析

分析测定了大田试验条件下11个玉米品种的3个氮肥处理、2个密度处理和6个生育期的150张叶片在350～2500nm波段的反射率和吸收率及其叶绿素a、叶绿素b和类胡萝卜素的含量。玉米叶片在叶绿素吸收波段的最大吸收波长位于665nm附近,665nm处叶片的吸收率与反射率间呈高度负相关(R2=-0.7533,n=150),而吸收率较高(>92%)的叶片的相关性明显强于吸收率较低的叶片。基于近红外波段和叶绿素吸收波段(红波段)或叶绿素反射波段(绿波段)构建的8个高光谱参量只有以反射率为基础计算时才与色素含量间存在相关性。mSR705和mND705无论以反射率还是以吸收率为基础计算,均表现出与色素含量间的强相关关系,而以吸收率为基础计算的mSR705和mND705与色素含量间的相关性又稍强于以反射率为基础计算的mSR705和mND705。本研究结果暗示叶片的表面反射是干扰叶片光谱(尤其是吸收光谱)对色素浓度变化响应的主要因子。

Comparison of the Leaf Hyperspectral Reflectance and Absorptance in Relation to the Leaf Pigment Contents in Corn Plants

A field experiment was carried out to investigate the relationship between leaf hyperspectral data including reflectance and absorptance and the leaf pigment(chlorophyll a,b and carotenoid) contents in corn plants.One hundred and fifty leaves were analyzed from eleven corn cultivars,three nitrogen level treatments and two population treatments at six growth stages.The wavelength of maximum absorptance value in the chlorophyll-absorbing region lay near 665 nm for the corn leaves.The leaf reflectance at 665 nm was robustly negatively correlated with the leaf absorptance at 665 nm with R2=0.753 3,n=150,and the better relationship was observed when the leaf absorptance at 665 nm was greater than 92%.The eight spectral indices constructed from the near infrared and red or green were not correlated with the leaf pigment if calculated based on the leaf absorptance.The mSR705 and mND705 indices either based on the leaf reflectance or on the leaf absorptance,appeared to be the strongest as related to the leaf pigments.The mSR705 and mND705 based on the absorptance were slightly better related to the leaf pigments than that based on the absorptance.The results in this study implicated that the leaf surface reflectance was the main factor interfering the response of the leaf spectra,especially that of the absorptance spectra,to the change in the leaf pigment content.