Infrared and Raman Spectroscopic Mapping and Imaging of Plant Materials

BackgroundThe essential oil is an important compound of the root and rhizome of medicinally used valerian (Valeriana officinalis L. s.l.), with a stated minimum content in the European pharmacopoeia. The essential oil is located in droplets, of which the position and distribution in the total root cross-section of different valerian varieties, root thicknesses and root horizons are determined in this study using an adapted fluorescence-microscopy and automatic imaging analysis method. The study was initiated by the following facts:A probable negative correlation between essential oil content and root thickness in selected single plants (elites), observed during the breeding of coarsely rooted valerian with high oil content.Higher essential oil content after careful hand-harvest and processing of the roots. ResultsIn preliminary tests, the existence of oil containing droplets in the outer and inner regions of the valerian roots was confirmed by histological techniques and light-microscopy, as well as Fourier-transform infrared spectroscopy. Based on this, fluorescence-microscopy followed by image analysis of entire root cross-sections, showed that a large number of oil droplets (on average 43% of total oil droplets) are located close to the root surface. The remaining oil droplets are located in the inner regions (parenchyma) and showed varying density gradients from the inner to the outer regions depending on genotype, root thickness and harvesting depth.ConclusionsFluorescence-microscopy is suitable to evaluate prevalence and distribution of essential oil droplets of valerian in entire root cross-sections. The oil droplet density gradient varies among genotypes. Genotypes with a linear rather than an exponential increase of oil droplet density from the inner to the outer parenchyma can be chosen for better stability during post-harvest processing. The negative correlation of essential oil content and root thickness as observed in our breeding material can be counteracted through a selection towards generally high oil droplet density levels, and large oil droplet sizes independent of root thickness.Electronic supplementary materialThe online version of this article (10.1186/s13007-018-0309-4) contains supplementary material, which is available to authorized users.

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“…These constituents include lipids, carbohydrates, and lignin, as well as secondary metabolites, e.g. terpenoids [ 41 ].…”

Section: Discussionmentioning

confidence: 99%

Characterization of essential oil distribution in the root cross-section of Valeriana officinalis L. s.l. by using histological imaging techniques

et al. 2018

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Section: Applications Of Spectroscopic Imaging In Plant-oriented Studmentioning

confidence: 99%

“…These continuously developing studies evidence the potential or IR imaging to monitor the temporal and spatial patterns in biochemistry, physiology, and microstructural features of plants during their development. IR imaging has become fairly matured tool in investigations of cell walls ( Schulz et al., 2014 ), with research activity being shifted towards applications of Raman imaging technique ( Prats Mateu et al., 2020 ). Nonetheless, recent attention is given to increasingly accessible IR imaging instrumentation utilizing high brightness radiation sources.…”

Section: Applications Of Spectroscopic Imaging In Plant-oriented Studmentioning

confidence: 99%

“…This technique demonstrated particular potential for elucidating structural and functional properties of cell walls. IR spectra in the region of 1200-950 cm -1 contain several characteristic peaks of the cell wall constituents (Schulz et al, 2014). For example, Monti et al (2013) reported that IR absorption at the following wavenumbers can be correlated with the molecular components of cell walls; 1,740, 1,595, 1,440, 1,150, 1,105, and 975 cm -1 (pectins); 1260, 1230 and 1075 cm -1 (hemicellulose); 1025 cm -1 (cellulose); additionally, refer to Table 1 for group frequencies.…”

Section: Investigations Of Microstructural Featuresmentioning

confidence: 99%

“…The present review aims to overview vibrational spectral imaging in the field of plant-related research. The methods in scope include infrared (IR), near-infrared (NIR) and Raman imaging ( Schulz et al., 2014 ). Additionally, fluorescence imaging is briefly overviewed; it is based on a different physical principle, yet gained profound use in plant science, e.g., in the studies of photosynthesis.…”

Section: Introductionmentioning

confidence: 99%

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Principles and Applications of Vibrational Spectroscopic Imaging in Plant Science: A Review

et al. 2020

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Detailed knowledge about plant chemical constituents and their distributions from organ level to sub-cellular level is of critical interest to basic and applied sciences. Spectral imaging techniques offer unparalleled advantages in that regard. The core advantage of these technologies is that they acquire spatially distributed semi-quantitative information of high specificity towards chemical constituents of plants. This forms invaluable asset in the studies on plant biochemical and structural features. In certain applications, non-invasive analysis is possible. The information harvested through spectral imaging can be used for exploration of plant biochemistry, physiology, metabolism, classification, and phenotyping among others, with significant gains for basic and applied research. This article aims to present a general perspective about vibrational spectral imaging/micro-spectroscopy in the context of plant research. Within the scope of this review are infrared (IR), near-infrared (NIR) and Raman imaging techniques. To better expose the potential and limitations of these techniques, fluorescence imaging is briefly overviewed as a method relatively less flexible but particularly powerful for the investigation of photosynthesis. Included is a brief introduction to the physical, instrumental, and data-analytical background essential for the applications of imaging techniques. The applications are discussed on the basis of recent literature.

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Raman spectroscopy – a visit to the literature on plant, food, and agricultural studies

Lemes

2024

J Sci Food Agric

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Raman spectroscopy, a fast, non‐invasive, and label‐free optical technique, has significantly advanced plant and food studies and precision agriculture by providing detailed molecular insights into biological tissues. Utilizing the Raman scattering effect generates unique spectral fingerprints that comprehensively analyze tissue composition, concentration, and molecular structure. These fingerprints are obtained without chemical additives or extensive sample preparation, making Raman spectroscopy particularly suitable for in‐field applications. Technological enhancements such as surface‐enhanced Raman scattering, Fourier‐transform‐Raman spectroscopy, and chemometrics have increased Raman spectroscopy sensitivity and precision. These and other advancements enable real‐time monitoring of compound translocation within plants and improve the detection of chemical and biological contaminants, essential for food safety and crop optimization. Integrating Raman spectroscopy into agronomic practices is transformative and marks a shift toward more sustainable farming activities. It assesses crop quality – as well as the quality of the food that originated from crop production – early plant stress detection and supports targeted breeding programs. Advanced data processing techniques and machine learning integration efficiently handle complex spectral data, providing a dynamic and detailed view of food conditions and plant health under varying environmental and biological stresses. As global agriculture faces the dual challenges of increasing productivity and sustainability, Raman spectroscopy stands out as an indispensable tool, enhancing farming practices' precision, food safety, and environmental compatibility. This review is intended to select and briefly comment on outstanding literature to give researchers, students, and consultants a reference for works of literature in Raman spectroscopy mainly focused on plant, food, and agronomic sciences. © 2024 Society of Chemical Industry.

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Infrared and Raman Spectroscopic Mapping and Imaging of Plant Materials

Cited by 5 publications

References 187 publications

Characterization of essential oil distribution in the root cross-section of Valeriana officinalis L. s.l. by using histological imaging techniques

Characterization of essential oil distribution in the root cross-section of Valeriana officinalis L. s.l. by using histological imaging techniques

Principles and Applications of Vibrational Spectroscopic Imaging in Plant Science: A Review

Raman spectroscopy – a visit to the literature on plant, food, and agricultural studies

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