Chinese cabbage was rapidly characterized using techniques of mid-infrared spectroscopy (diffusion reflectance spectroscopy,attenuated total reflectance spectroscopy and photoacoustic spectroscopy).The results show that the characteristics of different infrared spectra of Chinese cabbage are significantly different,which are demonstrated by the appearance,position and relative intensity of absorption bands.For the mid-infrared diffusion spectra,the main absorption bands are 2800-3800 cm-1 2200-2500 cm-1 1500-1700 cm-1and 1000-1500cm-1,for the attenuated total reflectance spectra there is only useful wavenumber region of 1200-1500 cm-1due to the strong interference of water,and for the photoacoustic spectra the main absorption bands are 2800-3800 cm-1,1500-1700 cm-1,1200-1500 cm-1 and 1000-1200 cm-1.The principal components analysis of infrared spectra indicates the principal component distributions are related to the nitrogen application rate,and there are linearly correlations between the first principal component and the nitrogen application rate,the regression coefficients (R)for diffusion reflectance spectra,attenuated total reflectance spectra and photoacoustic spectra are 0.9103、O.852 and 0.9366,respectively.Therefore,these three infrared techniques can be used in the rapid diagnosis of nitrogen nutrition of Chinese cabbage combining principal component analysis,and photoacoustic spectroscopy is more promising in the diagnosis of plant nutrition due to the convenient in situ measurement as well as depth-profiling function.%采用不同中红外光谱(漫反射光谱、衰减全反射光谱和光声光谱)对不同氮处理的小白菜进行表征.结果表明,小白菜不同的红外光谱具有明显不同的光谱特征,主要表现于峰形、峰位以及相对峰强度；中红外漫反射光谱的主要吸收峰分别为2800～3800 cm-1、2200～2500 cm-1、1500～1700 cm-1和1000～1500 cm-1,衰减全反射光谱由于水的强烈干扰可用的吸收峰主要在1200～1500 cm-1,而中红外光声光谱的主要吸收峰分别为2800～3800 cm-1、1500～1700 cm-1、1200～1500 cm-1和1000～1200 cm-1.漫反射光谱、衰减全反射光谱和光声光谱的主成分分析表明,不同氮处理主成分分布特征明显不同,且第一主成分(PCA1)均与施氮量显著相关,相关系数(r)分别为0.9103、0.8527和0.9366.这三种光谱利用主成分分布均可实现小白菜氮营养快速诊断,且光声光谱由于其独特的原位逐层扫描功能而表现出更好的诊断效果,在植物营养诊断中表现出较强的应用潜力.
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