不同干旱程度胁迫条件下烤烟叶片气孔导度的光谱响应

为了利用光谱信息快速、实时监测烤烟叶片气孔导度状况，以K326和中烟100两个品种为试验材料，分析了正常需水量、轻度干旱、中度干旱和重度干旱4种条件下的烤烟叶片气孔导度与冠层原始光谱及一阶导数光谱间的关系，筛选出烤烟气孔导度最佳敏感波段，并构建烤烟气孔导度状况估算模型。结果表明：(1)随着干旱胁迫程度的加剧，烤烟叶片气孔导度和700～1 350 nm波段处的冠层光谱反射率均呈现降低趋势，旺长期气孔导度高于伸根期和成熟期，两个品种表现规律一致。(2)敏感波段主要聚集在近红外光区域。715～930 nm、963～1 000 nm处的冠层原始光谱与烤烟叶片气孔导度相关系数达0.6以上，712～715 nm和718～719 nm处的光谱一阶导数与烤烟叶片气孔导度相关系数均达0.7以上，相关性均达到极显著水平。(3)利用711～715 nm处光谱一阶导数所构建的BP神经网络模型效果较好，模型决定系数R2为0.908。因此，利用烤烟冠层光谱一阶导数可较精准地反映烤烟叶片气孔导度状况，其建模效果优于冠层原始光谱，其中利用711～715 nm处光谱一阶导数构建的烤烟叶片气孔导度模型效果最优。

Spectral response of stomatal conductance of flue-cured tobacco leaves under different drought stress levels

In order to realize fast and real-time monitoring of stomatal conductance of flue-cured tobacco leaves with spectral information, two varieties, K326 and Zhongyan 100, were used as experimental materials to analyze the relationships between the stomatal conductance of leaves and the original spectra or the first derivative of the canopy spectra under the conditions of regular water needed, mild drought, moderate drought and severe drought. The best sensitive bands for the stomatal conductance of the flue-cured tobacco samples were screened, and the estimation model for the stomatal conductance was established. The results showed that: 1) With the increase of drought stress, the stomatal conductance of flue-cured tobacco leaves and the spectral reflectance of the canopy at 700- 1 350 nm presented a decreasing trend, and the stomatal conductance at the fast growing stage was higher than that at the root extending and maturity stages, and the two varieties had the same performance pattern. 2) The sensitive bands were mainly within the near-infrared region. The correlation coefficient between the original spectra of the canopy and the stomatal conductance of the tested leaves at 715-930 nm and 963-1 000 nm were more than 0.6, and the correlation coefficient between the first derivative of the spectra at 712-715 nm and 718-719 nm and the stomatal conductance of the leaves was more than 0.7, all the correlations reached an extremely significant level. 3) The BP neural network model established with the first derivative of the spectra at 711-715 nm was effective, and the determination coefficient R2 of the model was 0.908. Therefore, the first derivative of the flue-cured tobacco canopy spectra could reflect the stomatal conductance of the tested leaves more accurately, and its modeling effect was better than that of the original canopy spectra, in which the stomatal conductance model of the leaves established with the first derivative of the spectra at 711-715 nm showed the best effect.