Raman Imaging of Plant Cell Walls in Sections of Cucumis sativus

Abstract

Raman microspectra combine information on chemical composition of plant tissues with spatial information. The contributions from the building blocks of the cell walls in the Raman spectra of plant tissues can vary in the microscopic sub-structures of the tissue. Here, we discuss the analysis of 55 Raman maps of root, stem, and leaf tissues of Cucumis sativus, using different spectral contributions from cellulose and lignin in both univariate and multivariate imaging methods. Imaging based on hierarchical cluster analysis (HCA) and principal component analysis (PCA) indicates different substructures in the xylem cell walls of the different tissues. Using specific signals from the cell wall spectra, analysis of the whole set of different tissue sections based on the Raman images reveals differences in xylem tissue morphology. Due to the specifics of excitation of the Raman spectra in the visible wavelength range (532 nm), which is, e.g., in resonance with carotenoid species, effects of photobleaching and the possibility of exploiting depletion difference spectra for molecular characterization in Raman imaging of plants are discussed. The reported results provide both, specific information on the molecular composition of cucumber tissue Raman spectra, and general directions for future imaging studies in plant tissues.

Effect of Gelation Temperature on the Molecular Structure and Physicochemical Properties of the Curdlan Matrix: Spectroscopic and Microscopic Analyses

“…Raman spectra of 1,3-β- d -glucan matrices cross-linked at temperatures 80 °C and 90 °C are shown in Figure 4 A. For a more consistent comparative evaluation, the 1,3-β- d -glucan spectra were normalized to a band at 1092 cm −1 ( Figure 4 B) attributed to the stretching CC and CO stretching modes [ 36 ]. The band at approximately 1148 cm −1 is assigned to C-O-C vibrations of the glycosidic bond [ 28 ].…”

Overview of Popular Techniques of Raman Spectroscopy and Their Potential in the Study of Plant Tissues

“…Raman microspectroscopy provides spatial information on vibrations from complex biological samples, making it a very precise tool for the study of various plant materials [ 43 ]: pollen [ 44 , 45 ], fruit [ 46 , 47 ], roots [ 48 ], and wood of various origins [ 49 , 50 , 51 , 52 , 53 , 54 ]. Both the molecular composition and the molecular structure of the cell walls can be examined in the samples (example below Figure 2 ) [ 8 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ].…”

Background-suppressed SRS fingerprint imaging with a fully integrated system using a single optical parametric oscillator

“…Besides background suppression, our interest lies in whether we can visualize cell structures through their Raman resonance. Plant cell walls have been visualized by means of spontaneous Raman imaging in some recent works [32] [33]. In these studies, the Raman resonance of cellulose, peaking around 1090 cm −1 [34], was exploited; cellulose is the main constituent of these cells' walls.…”