Autofluorescence and HPLC analyses of phenolics in Zea mays L. stem cell walls

Cell walls from the internodes of various maize cultivars were analysed by ultraviolet fluorescence microscopy and histochemical staining before and after treatment with a number of chemicals known to extract wall substances. The material extracted with potassium hydroxide was quantitatively analysed with HPLC. This analysis showed an increase over time of the total cell-wall phenolic-acids in the ninth internode of different maize cultivars. During this time period however, the autofluorescence signal increased slightly in the parenchyma but decreased in the sclerenchyma. Chemical treatments of the cell walls of the various tissues effected different changes in the intensity of autofluorescence in these tissues. These differences help to explain the influence of cell-wall properties on the autofluorescence signal. The primary factor seems to be the amount of light penetration into the cell wall. This penetration depends on the packing of constituents which is a result of the structural and chemical composition of the cell wall.