Analysis of the Reflection Spectra of Pine Needles by the Method of Numerical Differentiation

The influence of aqueous solutions of H₂SO₄ on the spectral indices of pine needles has been investigated. It is shown that the first derivatives of the coefficients of reflection in the range 712.5–740.0 nm are most sensitive to changes in the content of chlorophyll and in the number of air spaces of mesophyll on exposure to acid solutions.     

不同病虫害危害程度下云南松针叶光谱模拟及其生化参数敏感性分析

明确植被叶片反射率对生化参数敏感程度是遥感定量反演生化参数含量的前提。本文以不同健康状态下的云南松针叶光谱为例,基于查找表法(LUT)对针叶光谱模型LIBERTY的叶绿素和水分吸收系数进行了标定。提出了一种新的光谱合成方法和枯黄指数YI,解决LIBERTY模型不能有效拟合严重受害程度的云南松针叶反射光谱曲线的问题。并应用EFAST全局敏感性分析方法,利用标定后的LIBERTY模型定量分析了不同受害程度的针叶生化参数敏感性变化。结果表明:(1)标定后的LIBERTY模型能有效拟合健康针叶光谱(R~2=0.999,RMSE0.01)、轻度(R~2=0.991,RMSE0.02)和中度受害针叶光谱(R~2=0.992,RMSE0.03);但是严重受害针叶光谱模拟能力很差(R~2=0.803,RMSE0.1)。(2)新光谱合成方法能有效拟合严重受害光谱(R~2=0.991,RMSE0.03);枯黄指数(YI)能够定量分析受害程度。(3)随着受害程度加深,针叶反射率对叶绿素、水分参数敏感度降低,而基吸收、白化吸收等参数敏感度增大,且存在敏感波段。如在505~565和705~850 nm范围白化吸收对针叶反射率作用明显;对于严重受害针叶,除了叶绿素之外白化吸收对可见光区针叶反射率影响也非常显著;通过引入白化吸收先验知识,发现如果能进一步确定白化吸收情况,能够提高严重受害针叶叶绿素反演的精度。     

松材线虫自然侵染后松树不同感病阶段针叶光谱特征变化

采用ASD野外光谱仪测量了黑松和马尾松在松材线虫自然侵染后不同感病阶段的反射光谱,分析了其中光谱特征参数及叶绿素变化情况.研究表明:(1)中红外波段反射光谱曲线对松树发病初期有一定的指示作用;(2)红边位置、绿峰高度、红谷反射率、红边斜率、水分胁迫波段反射率等参数的动态变化趋势与松材线虫侵染后两种松树的病害特征是一致的;(3)随病害程度加深两种松树叶绿素含量逐渐降低,且与光谱特征参数之间存显著线性关系.研究结果为利用高光谱遥感技术进行松材线虫病监测与预警提供参考,同时为针对不同发病阶段采用不同的措施治理松材线虫病提供新的实验依据.     

Method of Principal Components and Fourier Analysis of Brightness-Coefficient Spectra for Diagnostics of Pine Needles

The spectral brightness coefficients of pine needles exposed to aqueous solutions of sulfuric acid have been analyzed by the method of principal components and fast Fourier transform. Wavelengths informative for control of changes in the needles have been selected.     

黑松冠层反射光谱方向特征分析

松萎蔫病是松属树种的一种毁灭性病害，小范围甚至单木水平的森林病虫害的早期诊断对森林资源保护与可持续发展尤为重要。以感染松萎蔫病的黑松为研究对象，通过采集不同感病时期的黑松冠层的多角度光谱数据，分析不同特征波段的方向反射特征，总结不同感病程度黑松的冠层特征波段反射率的变化规律。结果显示：(1）在俯视观测时，在主平面方向的后向散射方向的反射率大于前向散射方向的反射率，并且在后向散射方向，四个波段的四个感病时期约在40°的观测天顶角出现热点效应；无论在主平面还是主垂面，蓝光波段（450 nm）与近红外波段（810 nm）的黑松冠层0°天顶角反射率呈现出感病初期＞健康＞感病中期＞感病末期的变化规律，红光波段（680 nm）和绿光波段（560 nm）的黑松冠层0°天顶角反射率呈现出健康≈感病初期＞感病中期≈感病末期的变化规律。在所有方位角，冠层反射率随着观测天顶角的增加而增大。(2）在仰视观测时，在主平面方向的后向散射方向的反射率小于前向散射方向的反射率，并且在方位角为0°时，4个波段反射率都是较大的；无论在主平面还是主垂面，蓝光波段（450 nm）绿光波段（560 nm）和红光波段（680 nm）的冠层反射率的大小呈现出感病初期＞健康>感病末期>感病中期的变化规律，近红外波段（810 nm）冠层反射率的大小呈现出感病初期＞健康>感病中期>感病末期的变化规律；在所有方位角，冠层反射率随着观测仰角的增加而减小。(3）黑松冠层反射光谱在俯视和仰视观测时，各个特征波段的二向性反射率的各向异性最强的是主平面，最弱的是主垂面，且主垂面的前向和后向反射率会呈现对称性，即“镜面反射”；各个特征波段在感病末期，黑松冠层反射率随观测天顶角的变化幅度较大，其他几个时期反射率随观测天顶角的变化幅度不明显。研究结果显示的树冠的不同角度的波段反射方向性特征为以后不同尺度的无人机监测的准确性与可靠性奠定基础，也为发展近地面便携式森林病虫害实时监测系统打下了基础。     

Application of NMR spectroscopy for analysis of the composition of pine needle essential oil

We have used ¹H and ¹³C NMR spectroscopy to analyze the chemical composition of essential oils of pine needles grown in different regions of the Republic of Belarus. We consider the change in the composition of the oils depending on the area where the pines were grown. We suggest using pine essential oil as a biological indicator of environmental conditions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 246–249, March–April, 2006.     

C-band scattering simulation of a Scots pine shoot

Scots pine (Pinus sylvestris L.) has the widest distribution of any pine and is one of the most important timber trees in Europe and one of the main species of boreal forest, which have an important role in climate change studies. The leaf area index (LAI) is one of the key input parameters for the climate change models. Recently a relationship between C-band backscattering and the LAI has been detected for Scots pine. To understand the C-band microwave characteristics of Scots pine shoots the backscattering is simulated using the so-called discrete dipole approximation (DDA), which is the only possible, nearly exact method for this problem. The backscattering of the shoot is dominated by the needles. The VV/HH backscattering ratio of closely spaced parallel and perpendicular shoots averages to that of a single shoot. For a simulated whole Scots pine crown the VV/HH backscattering ratio is related to the total orientation distribution of the needles. The variation range of the VV/HH backscattering ratio was 0.95-1.25, which is close to empirical values.     

土壤氧化铁的高光谱响应研究

通过分析野外采集的13个土种的不同氧化铁含量原始土样和人工配制不同氧化铁含量土样的高光谱特征,研究了氧化铁对土壤反射率、土壤线参数、土壤有机质高光谱特征、土壤反射率光谱曲线形态的影响。研究结果表明,随氧化铁含量的增加,350～570 nm波段反射率降低,570～2 500 nm波段的反射率增加,氧化铁去除量与反射率变化量之间的相关性不明显;氧化铁含量与土壤线斜率呈线性负相关,与截距呈线性正相关,且均达到极显著相关水平,表明利用土壤线参数反演氧化铁含量具有可行性;在622～851 nm波段,氧化铁对有机质的高光谱特征具有明显的抑制作用;通过去包络线和统计F值与光谱角值表明,氧化铁对土壤反射光谱曲线形态有影响。     

Effects of clear-cutting and soil preparation on natural 15N abundance in the soil and needles of two boreal conifer tree species

This study presents the impacts of clear-cutting and site preparation on soil and needle 15N-fractionation of Scots pine (Pinus sylvestris, L.) and Norway spruce (Picea abies (L.), Karst). Three microsites on different methods of site preparation were used: (i) mound (broken O/E/B horizons piled upside down over undisturbed humus), (ii) deep (exposed C-horizon) and (iii) shallow (exposed E/B horizon). We found significant differences between species, between closed forest and clear-cuts as well as between different site preparations. For instance, in the context of interspecific variations, the mean needle nitrogen concentrations of both seedlings (1.15,+/-0.10 %) and mature (1.09,+/-0.07 %) pine trees were significantly higher compared to corresponding needle concentrations of seedlings (0.88,+/-0.06 %) and mature trees (0.79,+/-0.02 %) of spruce. Similarly, we observed significantly more 15N-enriched needles of mature spruces (-4.0,+/-0.20 per thousand) as well as of seedlings (-5.0,+/-0.11 per thousand) relative to that of mature pine needles (-5.6,+/-0.10 per thousand) and seedlings (-6.0,+/-0.31 per thousand). These variations were assumed to be caused by the variation in mycorrhizal associations between the species. We assume that the proportion of mycorrhizal N-uptake of pines might have been larger than that of spruce. Regarding the clear-cut effects on N and 15N of both tree species, we observed that, in the mature natural stand, needle N concentrations of both pine (1.09,+/-0.07 %) and spruce (0.79,+/-0.02 %) tree species did not change significantly after clear-cutting (pine: 1.01,+/-0.06 %; spruce: 0.74,+/-0.04 % ). However, clear-cutting resulted in the significant increase in needle 15N natural abundance of both pine (-2.70,+/-0.06 per thousand) and spruce (-2.09,+/-0.05 per thousand) in comparison to that of natural stand (pine:-5.60,+/-0.10 per thousand; spruce:-4.00,+/-0.20 per thousand), which is assumed to be due to the increased level of nitrification and leaching of nitrate after clear-cutting. In the context of site preparation methods, soil and needle N were observed to be more 15N-enriched in deep and shallow treatment sites compared to that of closed forest site and untreated clear-cut site, which indicated that the main source of N uptake seems to be mainly directly from the soil of the corresponding horizons of mineral soil with higher delta15N.     

Spectral reflectance characteristics of different snow and snow-covered land surface objects and mixed spectrum fitting

The field spectroradiometer was used to measure spectra of different snow and snow-covered land surface objects in Beijing area.The result showed that for a pure snow spectrum,the snow reflectance peaks appeared from visible to 800 nm band locations;there was an obvious absorption valley of snow spectrum near 1 030 nm wavelength.Compared with fresh snow,the reflection peaks of the old snow and melting snow showed different degrees of decline in the ranges of 300～1 300,1 700～1 800 and 2 200～2 300 nm,the lowe...     

应用MXRF分析技术测定植物叶片中环境元素

应用一种使用X光透镜的微束X射线荧光(MXRF)分析技术, 对北京不同地区的松针中重金属元素及S元素含量进行了测定和分析, 探讨了它们与大气污染之间的关系; 根据受损松针与正常松针检测结果的比较, 确定了污染元素。 对小叶黄杨叶片中部进行了二维微区自动扫描, 得出了小叶黄杨叶片对各种金属元素的抗污染能力。 研究结果从方法学上验证了使用X光透镜的MXRF分析技术在测量环境样品中的应用, 为环境科研、 污染治理和环境管理提供了科学依据。     

不同含水量黑土土壤光谱反射率半经验模型构建

土壤含水量的变化情况与时空分布对热量平衡、农业墒情等具有显著的影响。利用反射率光谱信息反演土壤含水量的研究,可为实现土壤含水量速测、揭示土壤含水量时空变异规律提供科学依据。构建不同含水量黑土土壤反射率光谱半经验模型,深入探究土壤重量含水量与反射率光谱的关系。 制备了12种不同湿度的土壤样品。 采用ASD Field Spec Pro 3地物波谱仪对制备的不同湿度梯度的黑土土壤进行反射率光谱测量。 利用菲涅耳反射率建立土壤表面反射模型;在以往的研究中,Kubelka-Munk (KM)模型中的漫反射率R_∞通常被视为对于给定材料和照明波长的常数或需要反演的参数。通过研究发现,漫反射率R_∞不仅与材料和波长有关,还与土壤含水量相关。利用与土壤含水量相关的吸收系数及散射系数描述了土壤含水量与漫反射率R_∞的关系,并基于KM理论对体散射分量进行建模;进而构建不同含水量黑土土壤反射率光谱半经验模型。 根据实际测量数据选用最小二乘算法对模型参数进行反演,并通过分析反演参数简化模型。最后,将未参与建模的不同含水量梯度的数据代入模型中,验证模型的有效性。结果表明：对比不同含水量土壤反射率光谱的模拟值与实测值在400～2 400 nm波段范围内的模拟精度发现,含水量为200 g·kg-1的土壤反射率光谱的均方根误差最大,为0.008,含水量为40 g·kg-1的土壤反射率光谱的均方根误差最小,为0.000 6,不同含水量下土壤样品反射率光谱的均方根误差的均值是0.005 1。在400～2 400 nm波段范围内,不同波长下黑土土壤反射率光谱的预测均方根误差基本低于0.008,1 920 nm波长处的预测均方根误差最小,为0.002 062。采集长春地区的土壤检验模型的可靠性,配制15个不同含水量样品并对其进行反射率光谱测量。选取9个样品数据用于建模,6个样品数据用于验证。结果表明：在400～2 400 nm波段范围内,不同波长下的长春土壤反射率光谱的预测均方根误差基本低于0.015,525 nm波长处的预测均方根误差最小,为0.000 922 5。综上所述,所建立的模型具有很高的预测精度,可很好地适用于不同含水量黑土土壤反射率光谱的模拟。     

Effect of environment and heat treatment on the optical properties of RF-sputtered SnO2 thin films

Thin films of SnO₂ were deposited by RF-magnetron sputtering on quartz substrates at room temperature in an environment of Ar and O₂. The XRD pattern shows amorphous nature of the as-deposited films. The optical properties were studied using the reflectance and transmittance spectra. The estimated optical band gap (E_g) values increase from 4.15 to 4.3 eV as the Ar gas content decreases in the process gas environment. The refractive index exhibits an oscillatory behavior that is strongly dependent on the sputtering gas environment. The Urbach energy is found to decrease with increase in band gap. The band gap is found to decrease on annealing the film. The role of oxygen defects is explored in explaining the variation of optical parameters.     

基于多角度偏振载荷数据的中国典型地物偏振特性研究

相对于传统的光学遥感, 多角度偏振遥感不仅可以获取辐射强度信息, 而且可以获取偏振强度信息. 基于多角度偏振卫星载荷观测的中国典型地物的偏振反射率数据, 获取了地表偏振双向反射模型——Nadal模型的中国区域模型参数值. 在此基础上, 基于修正的Nadal模型研究了中国区域森林、草地、沙漠三种典型地物的多角度偏振特性. 研究表明: 1)各地物的偏振反射率均随着散射角的增大而减小, 随着太阳天顶角和卫星观测天顶角的增大而增大; 2)森林、草地和沙漠三种典型地表偏振反射率存在明显差别, 森林的偏振反射率最低, 草地的偏振反射率次之, 沙漠的偏振反射率大约为森林的两倍; 3)不同地物之间的偏振反射率差值均随着卫星观测天顶角和太阳天顶角的增大而增大. 研究结果可为基于多角度偏振遥感数据探测地表偏振特性和反演气溶胶参数提供先验知识.     

水胁迫下典型盐生植被梭梭光谱特征分析

荒漠地区由于气候干燥，降水稀少，水分常成为制约植被生长的因素之一，水分胁迫对植物长势和产量的影响比任何其他胁迫都要大。随着高光谱技术的发展，国内外已有众多学者利用高光谱数据研究植被遭受胁迫作用，然而这些研究对象多集中于甜菜、棉花、玉米、水稻等作物，针对干旱区盐生植被遭受胁迫作用的研究较少。梭梭作为荒漠、半荒漠地区的典型盐生植被之一，具有极高的经济和生态效益。选择梭梭作为研究对象，培育一年生梭梭，并设置三个水分梯度，形成受不同水分量胁迫的梭梭。使用原始光谱、红边位置参数，结合植被指数及二维相关光谱研究其叶片光谱特征，为干旱区利用高光谱遥感监测盐生植被提供借鉴。结果表明：(1)分析梭梭叶片反射光谱曲线发现，在可见光至中红外各波段范围内，受不同水分量胁迫作用的梭梭叶片光谱反射率有显著差异。在可见光(350～610 nm)波段，各水分处理的梭梭叶片反射率依次为100 mL>500 mL>200 mL，这是由于100和200 mL水分促进梭梭内部叶绿素合成，使该波段反射率降低，而过多的水分(500 mL)对梭梭内部的叶绿素合成没有更大的促进作用。在红光区(611～738 nm)，随着水分量的增多，受不同水分量胁迫的梭梭叶片光谱反射率依次减小。在738～1 181和1 228～1 296 nm波段，受不同水分量胁迫作用的梭梭叶片光谱反射率为：200 mL>100 mL>500 mL；在1 182～1 227 nm波段，受不同水分量胁迫作用的梭梭叶片光谱反射率为：100 mL>200 mL>500 mL。这是由于植被细胞结构对近红外区域的反射率影响较大，因而受不同水分胁迫作用的梭梭叶片光谱反射率有显著差异。在1 300～1 365和1 392～1 800 nm波段，受各水分胁迫作用的梭梭叶片反射率为：100 mL>200 mL>500 mL。这表明在500 mL水分胁迫量范围内，水分越多，叶子的细胞液、细胞膜对水分的吸收能力越强，使得反射率下降。通过对原始光谱求取一阶导数并提取红边位置参数发现，各水分处理下的梭梭叶片一阶微分光谱曲线中红边位置未发生移动。这是由于梭梭在长期的干旱环境影响下，形成了特殊的适应机制，水分对其红边位置影响不敏感。(2)选取若干植被指数分析各水分处理下的梭梭光谱指数变化。当水分胁迫量由100 mL增至200 mL时，WI/NDWI，MSI和NDII指数值变化显著，可用于研究水分胁迫下梭梭的光谱特征。(3)使用二维相关光谱技术分析受各水分胁迫作用的梭梭光谱特征，得出在100 mL水分胁迫下，在536，643，1 219和1 653 nm波段处，吸收峰对水分的微扰敏感；在200 mL水分胁迫下，在846和1 083 nm波段处，吸收峰对水分的微扰敏感；在500 mL水分胁迫下，在835和1 067 nm波段处，吸收峰对水分的微扰敏感。总之，在近红外波段，与100 mL水分量相比，梭梭受200和500 mL水分量胁迫时，吸收峰对水分的微扰敏感度上升。由100 mL水分胁迫下梭梭的二维同步相关谱图可知，1 044和1 665 nm，1 072和903 nm，903和1 264 nm，1 230和1 061 nm波段处形成正交叉峰，表明这些波段处光谱强度随水分的干扰同时变化。     

Effect of preparation and metal content on the introduction of Fe in BEA zeolite, studied by DR UV-vis, EPR and Mössbauer spectroscopy

Fe-containing SiBEA zeolites were prepared by a two-step postsynthesis method: creation of vacant T-sites by dealumination of tetraethylammonium BEA zeolite with nitric acid and then impregnation of the resulting SiBEA zeolite with an aqueous solution of Fe(NO₃)₃. X-ray diffraction shows that iron is incorporated in SiBEA at lattice sites. The presence of Fe in its oxidation state +3 and at isolated tetrahedral sites for low metal content, was demonstrated by diffuse reflectance UV-vis, EPR and Mössbauer spectroscopy. For high iron content, diffuse reflectance UV-vis and Mössbauer spectra revealed the additional presence of extra-lattice FeO_x oligomers and superparamagnetic Fe-oxyhydroxide. Mössbauer spectroscopy identified superparamagnetic Fe-oxyhydroxide as the main phase when basic conditions are used for the preparation.     

土壤矿物对松嫩平原主要土壤类型反射光谱特征的影响机理

尽管纯矿物的反射光谱特征分析与数据库建设工作已经开展,但土壤中各原生矿物、粘土矿物的测试主要是定性的,即能测定土壤中含有何种矿物,但难以测定准确的矿物组分含量。土壤矿物是土壤学与地质学的交叉点,易被忽视,特别是已有研究忽略了土壤矿物对土壤反射光谱曲线的影响。探讨了土壤矿物在可见光-近红外光谱部分(400~2 500 nm)对土壤反射光谱特征的影响,明确影响土壤反射光谱特征的主要机理。土壤样本于2014年采集于松嫩平原黑龙江部分,包括4个土类和7个土属,共54个土壤样本。土壤样本通过研磨、过筛后,在室内暗室中测得反射光谱数据,土壤矿物的反射光谱数据在2017美国地质调查局(USGS)最新矿物光谱库Spectral Library Version 7中获得,对反射光谱数据进行九点平滑、10 nm重采样和去包络线处理。土壤矿物含量测试采用荷兰Philip X’ Pert Pro 型X射线衍射仪分析样品的矿物组成,测试了土壤中石英、长石、方解石和闪石等原生矿物和蒙脱石、伊利石和高岭石等粘土矿物的含量。首先分析7个土属的反射光谱特征,明确每个土属反射光谱曲线的形状特征和吸收位置,其次分析土属的矿物含量情况,找出不同土属各矿物含量的共性和差异;再次分析不同粘土矿物和原生矿物的反射光谱特征,确定不同土壤矿物反射光谱曲线的形状特征和特征吸收的位置;最后将不同土属的反射光谱特征、不同土属的矿物含量情况和土壤矿物的反射光谱特征结合,得到如下结论：(1)土壤矿物决定了土壤反射光谱的骨架特征,土壤矿物对土属的反射光谱影响最明显,由于土类存在多种反射光谱特征,土壤矿物对土类的影响不明显。(2)粘土矿物对土壤反射光谱特征的影响大于原生矿物,主要受蒙脱石和伊利石等粘土矿物的影响,但砂性土受部分原生矿物的影响,主要是长石类矿物和高岭石的影响。(3)蒙脱石和伊利石分别决定土壤反射光谱的第一个吸收谷和第二个吸收谷特征,高岭石决定1 400和1 900 nm前的两个小吸收谷特征,钾长石和钠长石决定了砂性土的前两个吸收谷特征。(4)蒙脱石含量足够高时,会完全掩盖高岭石和长石类的反射光谱特征,部分掩盖伊利石的反射光谱特征;随着蒙脱石含量降低,伊利石的反射光谱特征逐渐体现;蒙脱石和伊利石的含量降到很低时,高岭石和长石类矿物的反射光谱特征逐渐体现出来。研究结果揭示了不同土属反射光谱特征差异的原因,可以为土壤反射光谱分类、土壤精细制图和基于高光谱图像的矿物分布研究等提供理论依据。     

不同粒径对土壤有机质含量可见—近红外光谱预测的影响

土壤有机质(SOM)是表征土壤肥力的重要指标,实现其快速准确检测可为精准农业区域管理提供有效的数据支撑。土壤粒径对SOM 的光谱预测及仪器开发有很大的影响,为了明确不同粒径对 SOM 预测的影响,分别制备了1～2,0.5～1,0.25～0.5,0.1～0.25和<0.1mm 五种均匀粒径及<1mm 混合粒径共计6种粒径土样并进行了可见-近红外(300～2 500nm)光谱数据采集。采用蒙特卡罗交叉验证分别剔除了不同粒径的异常样本,结合Savitzky-Golay卷积平滑法对光谱数据进行平滑去噪处理,比较了不同粒径样品的光谱反射率差异,并对平滑后的原始光谱 R进行倒数IR、对数 LR、一阶导数 FDR等3种光谱变换并分析与SOM 含量的相关性,基于竞争性自适应重加权算法(CARS)对光谱数据进行了特征波长提取,并结合偏最小二乘回归(PLSR)分别建立了相应的SOM 含量预测模型。结果表明,不同粒径土样的平均光谱反射率与变异系数随着粒径的减小逐渐增加,且在大于540nm 波长范围内,差异明显。随着粒径的减小,SOM含量与光谱反射率在全波段范围的相关性变化幅度愈加明显,FDR 变...     

基于反射率模拟模型的黑土有机质含量估测

定量分析了黑龙江省黑土室内高光谱反射率曲线特征,确定了影响反射光谱曲线的主要特征控制点,建立了黑土光谱反射率模拟模型并对其进行评价,分析比较反射率数据、模拟后的光谱数据与土壤有机质含量的关系,建立了土壤有机质含量光谱预测模型。结果如下：有机质是小于1 000 nm范围黑土反射光谱特征的决定因素,随有机质含量变化,黑土光谱反射率在该范围呈现单/双吸收谷特征;黑土反射光谱曲线在450～930 nm范围内有５个主要特征控制点;黑土反射率模拟模型能较准确地描述黑土反射光谱曲线,直线模型的模拟效果更好;以反射率模拟模型系数为自变量的有机质含量预测模型优于基于反射率及其一阶微分的模型,说明反射率模拟模型的曲线控制点选择合理且有代表性,反射率曲线模拟方法能够准确描述黑土的实际光谱反射率。     

Investigation of the manganese stress on wheat plant by attenuated total reflectance Fourier transform infrared spectroscopy

ABSTRACT

The present paper deals with the investigation of the changes in chemical contents of the leaf of wheat seedling stressed by excess manganese using attenuated total reflectance Fourier transform infrared spectroscopy (FTIR) technique. The infrared spectra of the leaves of control and manganese-treated wheat plants have been recorded in the spectral region 485–4000?cm^?1 at a resolution of 4?cm^?1. The recorded spectrum has been analyzed with the help of curve-fitting method for the quantitative estimation of chemical contents and conformational changes. The study indicated changes arising in the polysaccharide, lignin, amino acid, secondary structure of protein, and lipid in the leaves of control and manganese-treated wheat plants. Manganese treatment increased the amount of cellulose, lignin, and amide II till 200?μM concentration, while a decrease was observed at 1000?µM concentration. Manganese induced conformational changes in the secondary structure of protein which was indicated by shifting of the bands to the higher wavenumber and change in the β sheet/α helix ratio. In addition, manganese stress decreased lipid content in the leaves of the wheat seedlings. The study demonstrates the potential of attenuated total reflectance FTIR for the non-invasive and rapid monitoring of the plants stressed with heavy metals.