不同水分处理对烟草叶片高光谱及红边特征的影响

采用ASD Fieldspec HH光谱仪, 测定了不同水分处理下两个烟草品种叶片的光谱特性, 分析其红边特征参数的变化规律及其与烟叶生理指标的相关性。结果表明: 不同水分处理之间的烟草叶片光谱反射率差异明显, 但两个品种的变化规律一致。烟草伸根期和旺长期, 近红外光区的光谱反射率随土壤水分的增加而升高, 成熟期则呈相反趋势, 且光谱反射率在旺长期达到最高值。不同水分处理下烟草叶片一阶微分光谱趋势总体一致, 但红边一阶导数光谱差异显著。红边位置随土壤水分减少向长波方向移动, 发生“红移”现象。红边幅值和红边面积在伸根期和旺长期均随土壤含水量的增加而发生“红移”现象, 成熟期则发生“蓝移”现象。烟草叶片的红边位置同其生理指标的相关性要优于其他参数, 同叶绿素a含量、叶绿素b含量、类胡萝卜素含量、叶绿素总量、叶片鲜重、叶片干重、叶面积和叶片含水率均呈极显著相关关系; 红边幅值和红边面积与叶绿素a含量、叶绿素b含量、类胡萝卜素含量、叶绿素总量和叶片含水率之间均呈极显著性正相关, 红边面积同叶片干重呈极显著性负相关关系。

Effect of water condition on hyperspectral and red-edge characteristics of tobacco leaf

Red-edge characteristics of two cultivars of tobacco under different water treatments were analyzed by measuring leaf spectra with ASD Fieldspec HH. The relationship between red-edge parameters and physiological indices of tobacco was also determined. The results showed notable differences between leaf spectral reflectance of the two cultivars under different water treatments. However, the trend of change in spectral reflectance was similar in the two cultivars. While near-infrared band reflectance increased with increasing soil moisture during root elongation and vigorous growth stages, it decreased at mature stage. Leaf spectral reflectance was highest at vigorous growth stage. Though first differential spectra of red-edge of tobacco leaf showed similar tends, first derivative spectra were significantly different under different treatments. Red-edge position shifted from short to long wavelength with decreasing soil moisture, causing red shift during tobacco entire growth period. While the slope and area of red-edge increased at root elongation and vigorous growth stages (characterized as red shift), they shifted from long to short wavelength at mature stage (characterized as blue shift). The correlations of red-edge position with physiological indices of tobacco leaf were more significant than those with red-edge slope and area. There were significant correlations among red-edge position with contents of chlorophyll a, chlorophyll b, chlorophyll a+b and carotenoid; leaf fresh-weight, leaf dry-weight, leaf area and leaf moisture contents. There were also significant positive correlations among red-edge slope and area with chlorophyll a, chlorophyll b, chlorophyll a+b, carotenoid and leaf moisture contents. The correlation between red-edge area and leaf dry-weight was negative.