傅里叶变换红外光谱技术评估玉米器官含氮量的可行性研究

A feasibility study on assessing nitrogen content in maize organsusing Fourier transform infrared spectroscopy

探究傅里叶红外光谱(FTIR)技术评估作物器官含氮量的可行性,对快速掌握作物氮素状况、优化氮肥管理具有重要意义。利用低分子量较少的腐植酸(HA1)和低分子量较多的腐植酸(HA2)开展玉米水培试验,通过设置不同的腐植酸浓度短期内获得了器官氮素含量差异较大的植物样品;在测定/采集玉米各器官含氮量与FTIR光谱数据的基础上,利用主成分分析方法探究了玉米各器官含氮量与FTIR特定波数吸光度的相关性,以明确可用于评价玉米样品含氮量的FTIR特征参数。结果显示:(1)不同浓度HA1与HA2对玉米各器官含氮量产生了差异化影响,表现为2.5 mg·L^(–1)HA1显著提高了叶片、茎秆及根系的含氮量(P<0.05),含氮量较对照分别提高20.8%,19.9%以及64.2%,但各器官含氮量随HA1浓度的提高呈降低趋势,当HA1浓度达到25 mg·L^(–1)时,各器官含氮量均低于对照;HA2整体上提高了各器官的含氮量,其中显著提高了根系含氮量,提高幅度达到了35.0%~45.4%。(2)不同浓度HA1与HA2对玉米各器官在1 051.0、1 159.0、1 247.7、1 635.3、1 650.8、1 731.8以及2 919.7 cm^(–1)处FTIR吸光度的影响与含氮量相似,即各浓度HA2与低浓度HA1可提高玉米器官蛋白质、脂类、糖类等有机组分的含量。(3)主成分分析结果表明,与叶片含氮量高度相关的3个特征波数分别为1 635.3、1 247.7以及1 159.0 cm^(–1);茎秆为1 650.8和1 159.0以及1 247.7 cm^(–1);根系为1 635.3、1 650.8以及1 159.0 cm^(–1),即比较玉米各器官上述波数处FTIR的吸光度可用于评估玉米样品的含氮量,吸光度越高,含氮量越高。通过比较玉米各器官FTIR特定波数处的吸光度可以初步评估不同农艺措施对玉米各器官含氮量的影响,这为将来FTIR在植物氮素营养诊断方面的应用提供了重要参考。

It is important to study the feasibility of using Fourier transform infrared spectroscopy(FTIR)to evaluate the nitrogen(N)content in crop organs rapidly and optimize N fertilizer management.In this study,hydroponic experiments were carried out on maize using humic acid with low molecular weight(HA1)and high molecular weight(HA2)as fertilizers.By setting different concentrations of HA1 and HA2,plant samples with significant differences in organ N content in the short term were obtained.On the basis of measuring/collecting the N content and FTIR spectra of different maize organs,the relationship between the N content and the absorbance at the specific wave number of FTIR was investigated by principal component analysis(PCA),and the FTIR characteristic parameters for the evaluation of N content in maize samples were determined.The result showed that:(1)The effects of different concentrations of HA1 and HA2 on the N content of various maize organs were distinguishable.At a concentration of 2.5 mg·L^(–1),HA1 significantly increased the N content of leaves,stems,and roots(P<0.05)by 20.8%,19.9%,and 64.2%,respectively,as compared to the control.However, as the HA1 concentration increased, the N content of each organ showed a downward trend. When theHA1 concentration reached 25 mg·L^(–1), the N content of all organs was lower than the control. On the other hand,HA2 generally increased the N content of all organs, with a significant increase by 35.0% – 45.4% in the roots (P< 0.05). (2) The impact of varying concentrations of HA1 and HA2 on the absorption of FTIR at different wavenumbers (1 051.0, 1 159.0, 1 247.7, 1 635.3, 1 650.8, 1 731.8 and 2 919.7 cm^(–1)) in different organs mirrored theireffects on N content. In other words, higher concentrations of HA2 and low concentrations of HA1 could increasethe contents of organic components, such as proteins, lipids, and carbohydrates in maize organs. (3) The results ofprincipal component analysis revealed that the three characteristic wavenumbers were highly correlated with N content, 1 635.3, 1 247.7 and 1 159.0 cm^(–1)for the leaves, 1 650.8, 1 159.0 and 1 247.7 cm^(–1)for the stems, and 1 635.3,1 650.8 and 1 159.0 cm^(–1)for the roots. Therefore, the absorbance of FTIR at these wavenumbers can be utilized toassess the N content in maize samples, with higher absorbance indicating a higher N content. By comparing theFTIR absorbance at specific wave numbers in different organs of maize, the effects of different agriculturalmeasures on the N content of maize organs can be preliminarily evaluated. The result provides an important reference for the future application of FTIR in the diagnosis of plant N nutrition.