Development of the Water Stress Diagnostic Technology of the Citrus using Spectral Measurement and Granier Method

本研究利用光谱测量和Granier法，建立了柑橘水分胁迫诊断技术。在田间试验中，选用了价格低廉、测量速度快的商用传感器。半椭圆模型计算的总叶面积与计算总叶数得到的总叶面积具有非常高的相关性（r=0.897）。利用价格低廉的鱼眼镜头数码相机，提出了一种非接触、无损、高精度估算总叶面积的方法。此外，我们采用Granier法，尝试测量覆膜栽培下柑橘树的蒸腾流量。结果表明，白地膜截雨造成的土壤干燥对树木造成干燥胁迫，降低了树木的蒸腾速率。在此基础上，研究了利用近红外光谱分析仪对柑桔叶片水势进行无损检测的方法。对各波长（1300 ~ 2400nm） 1061个测量值计算的8种主要成分进行PLS回归分析，预测精度R=0.817，差值SEP=0.300MPa，偏差=0.004MPa。由此可见，利用红外光谱法对柑桔叶片水势进行无损估测是可行的。

In this study, water stress diagnostic technology of the citrus using spectral measurement and Granier method was developed. The commercial sensor was selected as one that can measure soil moisture inexpensively and quickly at field experiment. Very high correlation (r=0.897) was acquired between the total leaf area calculated from the half-ellipse model, and the total leaf area obtained by counting the number of total leaves. The technology of estimating the total leaf area by non-contact and non-destructive method with high precision was developed using the inexpensive digital camera with a fish-eye lens. Moreover, we used the Granier method and tried measuring the transpiration flow rate of the citrus tree under the mulch-cultivation. Consequently, it was shown clearly that the soil dryness by rain interception of white mulch sheet gives dryness stress to a tree, and reduces the transpiration flow rate. Furthermore, the non-destructive technique of estimating the leaf water potential of a citrus leaf was examined using near infrared spectral analyzer. In PLS regression analysis of the eight main ingredients which calculated from the all of 1,061 measurements at each wavelength (1300-2400nm), the high prediction accuracy of R=0.817, difference SEP=0.300MPa, and Bias=0.004MPa was acquired. From this, it became clear that the water potential of a citrus leaf could be estimated by non-destructive method using an infrared spectrum method.