Measurement of Nitrate Concentration Distribution in Vegetables by Near-Infrared Hyperspectral Imaging
Measurement of Nitrate Concentration Distribution in Vegetables by Near-Infrared Hyperspectral Imaging
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DOI：
10.2525/ecb.48.37
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发表时间：
2010-06
期刊：
影响因子：
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通讯作者：
H. Itoh;Shinsuke Kanda;H. Matsuura;N. Shiraishi;K. Sakai;A. Sasao
中科院分区：
文献类型：
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作者：
H. Itoh;Shinsuke Kanda;H. Matsuura;N. Shiraishi;K. Sakai;A. Sasao
本研究的目的是开发一种基于实验室的近红外（NIR）高光谱成像系统来测量二维分布的硝酸盐浓度在蔬菜叶片作为一种工具，精确分析硝酸盐代谢。小松叶片进行了分析，高光谱反射率在607至967 nm的范围内，分辨率为9 nm。通过参考板标准化反射率，并将其转换为相对反射率。结合偏最小二乘（PLS）回归和主成分回归（PCR），提出了一种选择有效波长预测硝酸盐浓度的算法。至于预处理方法的光谱，平均中心和标准的正常变量转换进行了检查。通过标准误加权平均值（WSE）评价模型的估计精度。与全谱模型（41个波长）相比，波长选择模型的估计精度有所提高，且WSE较小。使用21个波长的校准模型实现了1446 ppm的最佳WSE，相关系数为0.870。小松叶片中的硝酸盐分布在空间分辨率为2.5×10−4 mm/像素的数字图像中可视化。这些图像表明，营养物质的运输路线中含有较高的硝酸根离子浓度比其他地区的小松叶片。
The purpose of this research is to develop a laboratory-based near-infrared (NIR) hyperspectral imaging system to measure the two-dimensional distribution of nitrate concentrations in a vegetable leaf as a tool for precisely analysing nitrate metabolism. Komatsuna leaves were analyzed by hyperspectral reflectance in the range from 607 to 967 nm with a resolution of 9 nm. The reflectance was standardized by a reference plate and was converted to relative reflectance. An algorithm to select the effective wavelength to predict the nitrate concentration was developed in conjunction with partial least squares (PLS) regression and principal components regression (PCR). As for preprocessing methods for the spectra, mean-centre and standard normal variate transformations were examined. Estimation accuracy of the developed models was evaluated by the weighted average of standard error (WSE). The estimation accuracy of the wavelength-selected models was improved and the WSE was smaller than that of the full-spectrum model (41 wavelengths). The calibration model that used 21 wavelengths achieved the best WSE of 1446 ppm with a correlation coefficient of 0.870. The nitrate distribution in Komatsuna leaves were visualized in digital images with a spatial resolution of 2.5×10−4 mm/pixel. These images showed that the transporting route of nutrients contains higher nitrate ion concentration than other areas in the Komatsuna leaf.