Fourier transform infrared spectroscopy as a non-destructive method for analysing herbarium specimens

Dried plant specimens stored in herbaria are an untapped treasure chest of information on environmental conditions, plant evolution and change over many hundreds of years. Due to their delicate nature and irreplaceability, there is limited access for analysis to these sensitive samples, particularly where chemical data is obtained using destructive techniques. Fourier transform infrared spectroscopy (FTIR) is a chemical analysis technique that can be applied non-destructively to understand chemical bonding information and therefore functional groups within the sample. This provides the potential for understanding geographic, spatial and species-specific variation in plant biochemistry. Here we demonstrate the use of mid-FTIR microspectroscopy for the analysis of Drosera rotundifolia herbaria specimens, which were collected 100 years apart from different locations. Principal component and hierarchical clustering analysis enabled successful differentiation between three main regions on th..., Sample Collection Four D. rotundifolia herbarium specimens were used in this study (Table 1, Figure S1). Two of the specimens were plants collected in 2021 from the same location, at the same time by the same collector. The other two specimens were collected from a different location but were collected at the same place on the same date in 1934. All samples were in dried form with no observable moisture. FTIR Specimens were carefully removed from the herbarium sheet and placed onto the sample stage. FTIR spectra were taken for each of three tissue types (Fig. 1: lamina, tentacle stalk, tentacle head), on two leaves, for each of the four specimens. In each area, three replica FTIR spectra maps were produced. Each map consisted of roughly 15 points depending on area size (minimum = 8, maximum = 20). Infrared spectra were taken using a Thermo Nicolet iN10mx spectrometer fitted with a liquid-nitrogen-cooled MCT detector. Spectra were captured in transmission mode, with an 80 × 80 µm apertur...,保存在标本馆中的干燥植物标本，是蕴藏着数百年间环境状况、植物演化与变迁信息的未被充分发掘的宝库。由于此类标本质地脆弱且不可替代，对这些珍贵样本开展分析的途径十分有限，在使用破坏性技术获取化学数据的场景中这一局限尤为突出。傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy, FTIR）是一种可无损应用的化学分析技术，能够获取样本内的化学键信息，进而解析其中的官能团。该技术为探究植物生物化学特征的地理、空间及物种特异性差异提供了可能。本研究展示了中红外傅里叶变换显微光谱技术在圆叶茅膏菜（Drosera rotundifolia）标本馆标本分析中的应用，这些标本采集自不同地点，采集时间跨度达百年之久。主成分分析与系统聚类分析可成功区分样本上的三个主要区域…… 样本采集 本研究共使用4份圆叶茅膏菜标本馆标本（见表1、补充图S1）。其中2份标本于2021年由同一采集者在同一地点、同一时间采集；另外2份标本则于1934年在另一地点的同一位置、同一日期采集。所有样本均为干燥状态，无可见水分。 傅里叶变换红外光谱测试 将标本小心从标本台纸上取下并放置于样品台。针对4份标本的2片叶片，分别对3种组织类型（图1：叶片、触手柄、触手头）采集傅里叶变换红外光谱。每个区域均采集3组重复的红外光谱图谱，每张图谱依据区域大小包含约15个采样点（最少8个，最多20个）。红外光谱采集使用配备液氮冷却型汞镉碲（Mercury Cadmium Telluride, MCT）探测器的Thermo Nicolet iN10mx型光谱仪，采用透射模式，孔径为80×80 µm……