A Cytochemical Investigation of the Lateral Walls of Dianthus Vessels. Differentiation and Pit-Membrane Formation

The deposition of cell wall polysaccharides and subsequent lignin incrustation were followed during vessel differentiation in carnation stems. In the secondary walls, lignin deposition was closely accompanied by an apparent loss of free vic-glycol groups from polysaccharides. This apparent loss could be related to the progressive binding of lignin molecules to cell wall carbohydrates. The intensity of lignification in mature intervessel primary walls exhibited a positive gradient from the earliest- to the latestformed metaxylem elements. Intervessel pitmembrane hydrolysis appeared as a sequential and ordered process. A partial hydrolysis of the vessel primary wall was sometimes observed in vessel-to-parenchyma pits.