摘 要 ：运用导数光谱分析技术，研究了不同氮肥水平下不同品种油菜(Brassica napus)的 叶面积指数（Leaf area index， LAI）及角果皮面积指数 （Pod area index，PAI ）与冠层导数光谱及其衍生参数的定量关系。结果表明，油菜导数光谱与花前LAI和花后PAI均有良好的相关关系，在 750 nm附近相关关系最好，相关系数达到0.9左右。三边参数与油菜LAI和PAI的相关性顺序为：红边＞黄边＞蓝边，面积参数＞振幅参数＞位置 参数。油菜红边导数光谱的双峰现象降低了红边位置对油菜LAI和PAI的敏感程度，利用线性外推法拟合红边位置能 提高其对油菜LAI和PAI的敏 感程度。在三边参数及其衍生参数中，红边面积及其与蓝边面积的差与LAI及PAI的相关性最好,且适用于该研究中使用的不同品种。因此，750 nm 处的一阶导数光谱、红边面积及其与蓝边面积的差可用于有效地监测油菜的光合器官面积。
Abstract:Aims Crop canopy reflectance, especially derivative spectrum, is a promising prospect for nondestructive rapid estimation of crop photosynthetic organ area and evaluation of crop growth status and yields. The purpose of our experiment was to investigate the quantitative relationships between derivative spectral parameters and photosynthetic organ area. Methods We used field experiments to study leaf area index (LAI), pod area index (PAI) and canopy hyperspectra reflectance of rapeseed (Brassica napus) under different nitrogen levels and in different cultivars and determined quantitative relationships between derivative spectral parameters and photosynthetic organ area. Important findings The correlation coefficient between photosynthetic organ area and derivative spectra was higher than that of canopy spectral reflectance of single band, with the best correlation at 750 nm (r=0.9). The correlation sequence of “three-edge parameters" to photosynthetic organ area was red edge＞yellow edge＞blue edge, area parameters＞amplitude parameters＞position parameters. Phenomenon of “two peak" at red edge of rape canopy spectra weakened the sensitivity of red edge position (REP) to changes of biophysical parameters, but REP extracted from linear extrapolation method (REP(le) ) strengthened it. Red edge area (SDr) and difference of SDr and blue edge area (SDb) (DSDr,b) from “three-edge parameters" and their derived parameters had the best correlation with LAI and PAI, and they were suitable for the different cultivars used in this study. Therefore, derivative spectral parameters, i.e., first derivative spectrum at 750 nm, SDr and DSDr,b could be used to effectively monitor area of photosynthetic organs in rapeseed.