Xylem characterization using improved pseudo-Schiff propidium iodide staining of whole mount samples and confocal laser-scanning microscopy

Abstract

An improved pseudo-Schiff propidium iodide staining technique well suited for, but not limited to, the visualization of xylem cell walls in whole mount samples is presented. The pseudo-Schiff reaction results in covalent binding of the fluorescent dye propidium iodide to cell walls. This stable linkage permits the use of clearing agents after staining, which is itself improved following pretreatment of the plant tissue. A subsequent acid alcohol washing step eliminates unbound propidium iodide to reduce background fluorescence. The method can be used for characterizing xylem cell structure in different organs and species without the need for tissue sectioning.