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

<p>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 <em>Drosera</em> <em>rotundifolia</em> 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 the plant (lamina, tentacle stalk and tentacle head), and between the different specimens. Lipids and protein spectral regions were particularly sensitive differentiators of plant tissues. Differences between the different sets of specimens were smaller. This study demonstrates that relevant information can be extracted from herbarium specimens using FTIR, with little impact on the specimens. FTIR therefore provides the potential as a powerful tool to unlock historic information within herbaria.</p>