在分析冬小麦生长期冠层反射光谱和叶绿素含量变化特征的基础上,对二者之间的相关性进行了研究。 表明从小麦拔节期开始,冠层反射光谱在可见光区(400-750 nm)的反射率先降低而后升高,以孕穗期反射率最低;在近红外区(750-1000 nm)冠层反射率由拔节期至孕穗期反射率降低,然后开始上升。 扬花期上升至最高点后又开始下降,直至乳熟期降至最低。 冬小麦冠层反射率与叶绿素含量相关分析结果表明,冬小麦拔节期和孕穗期二者呈正相关,扬花期二者呈负相关;整个生长期中,孕穗期可见光区552 nm处反射率与叶绿素含量相关系数最大达0.89。 依据冬小麦生长期冠层反射光谱红边拐点位置, 分别建立了拔节期叶绿素含量线性检测模型(R2=0.92)和孕穗期二项式模型(R2=0.91),用于冬小麦叶绿素含量的无损检测是可行的。

The canopy spectral reflectance and chlorophyll content of winter wheat were measured and analyzed in the whole growing season. The characteristics of canopy spectral reflectance indicated that the canopy spectral reflectance changed significantly at different stages. It decreased first and increased later with growth progress in the visible region (400-750 nm) after jointing stage,then the reflectance was lowest at booting stage. In near-infrared region (750-1 000 nm) the spectral reflectance climbed sharply. The canopy reflectance was declined at booting stage and rose to the highest point at flowering stage. It dropped to minimum level subsequently at milk-ripe stage. However,the spectral reflectance characteristics at jointing stage and booting stage were used to detect the chlorophyll content. High correlation was observed between the canopy spectral reflectance and chlorophyll content. The positive correlation of canopy spectral reflectance with chlorophyll content was found at jointing stage and booting stage. Because the plant spectral reflectance was effected by chlorophyll greatly in visible region,the correlation coefficient reached 0.89 at 552 nm in booting stage. On the contrary,there was a negative correlation at flowering stage. Meanwhile,the red edge inflection point as one of the most important spectral parameters was analyzed at winter wheat growth stages based on the first derivative of reflectance spectra. The relation between the red edge inflection point and chlorophyll content was observed in each plot and the analysis results illustrated that the red edge inflection points could help detect the chlorophyll content at jointing stage and booting stage. The linear model of chlorophyll content with red edge inflection points was built at jointing stage (R2=0.92). High correlation was found between thered edge inflection point and chlorophyll content at booting stage. It was showed that the binomial model (R2=0.91) was better than linear model (R2=0.73). It was indicated that using spectral analysis to detect the winter wheat chlorophyll content non-destructively was feasible. The obtained conclusions also provided theoretical basis for further researches on measuring methods of chlorophyll content in the field.