烤烟冠层光谱参数与叶片叶绿素含量的相关分析

Correlations between canopy reflectance spectrum parameters and leaf chlorophyll content of flue-cured tobacco (Nicotiana tabacum L.)

为了明确烤烟冠层光谱参数与叶片叶绿素含量的相关性,测定了不同氮肥施用量条件下烤烟冠层光谱特征和烤烟鲜烟叶片叶绿素a(Chl-a)、叶绿素b(Chl-b)、类胡萝卜素(Cars)含量,并对光谱参数与叶绿素含量进行了相关分析和回归分析。结果表明:随着氮肥施用量增加,团棵期和旺长期鲜烟叶片的Chl-a、Chl-b和Cars含量均增加,可见光波段反射率降低、近红外波段反射率增加;而打顶期叶片的3种色素含量和光谱特征的变化规律不明显。可见光460～670nm范围内,460nm反射率与叶片叶绿素含量呈显著正相关,其他波段反射率与叶片叶绿素的含量呈显著负相关;近红外780～1260nm范围内,所有波段与叶片叶绿素含量的都呈显著正相关,1480nm反射率与叶片叶绿素含量呈显著负相关。反映Chl-a、Chl-b、Cars含量与光谱参数——比值植被指数(ratio vegetation index,RVI)定量关系的最佳回归方程分别为幂函数、幂函数和指数函数:Chl-a=0.250RVI(730,550)1.511,Chl-b=0.049RVI(730,550)1.841,Cars=0.0998e0.379RVI(730,550)。

To determine the correlativity between canopy reflectance parameters and leaf chlorophyll content of flue-cured tobacco, this paper measured the canopy reflectance spectrum and the contents of leaf chlorophyll a （Chl-a）, chlorophyll b （Chl-b）, and carotenoid （Cars） under different N application rate, and analyzed the correlations between the spectrum parameters and the chlorophyll contents. With the increase of N application rate, the contents of fresh leaf Chl-a, Chl-b, and Cars at spherical plant stage and fast growing stage all increased, and the reflection in near infrared bands enhanced but that in visible bands decreased. At topping stage, the contents of Chl-a, Chl-b, and Cars and the canopy reflectance did not present notable changing trend. Within the visible bands, the reflection of 460 nm was significantly positively correlated with the contents of Chl-a, Chl-b, and Cars, while the reflection of other bands was significantly negatively correlated with the contents of the three pigments. Within the near infrared bands, the reflection of 1480 nm was significantly negatively correlated with the contents of Chl-a, Chl-b, and Cars, while the reflection of other bands was significantly positively correlated with the contents of the three pigments. The best regression equations to determine the quantitative relations between the contents of fresh leaf Chl-a, Chl-b, and Cars and the spectrum parameter （ratio vegetation index, RVI） were power function, power function, and exponential function respectively, i.e., Chl-a=0.250RVI（730,550）^1.511, Chl-b=0.049RVI（730,550）^1.841, and Cars=0.0998e^0.379 RVI（730,550）.