Spatial Distribution of Phenolic Materials in Durum Wheat Grain as Probed by Confocal Fluorescence Spectral Imaging

Abstract

Microspectrofluorometry has been employed to study the spatial distribution of phenolic material in cereal grain. Transverse sections of the grain were used for the spectral characterisation of different molecular species present inTriticum durumgrains. Auto-fluorescence emission spectra were recorded on micro regions of each section. The analysis of the whole set of spectra permitted the characterisation of three principal spectral features; indicators of phenolics in specific regions of wheat sections. The comparison with model reference spectra showed that spectral components could be attributed to ferulic and p-coumaric acids. Using these spectral components, spectral fluorescence imaging was performed allowing the relative fluorescence intensity of each phenolic feature to be mapped. Images generated were used for the generation of the 3D organisation of auto-fluorescent phenolic materials within the grain. This new and rapid method was further used for the spectral characterisation of the various aleurone cell walls with high sensitivity. Analysis of the data showed that outer and inner aleurone cell walls exhibited similar fluorescence profiles but with significantly different intensities.