Study on the cross-links between wall polysaccharides by dehydrodimers of hydroxycinnamic acids during the cessation of cell elongation

In this paper, the position of crossing linkage between cell wall polysaccharides was studied by determining the digestibility of pectin-depleted walls, the contents of hydrocinamic acids and their dimmers in each fraction of elongated and non-elongated cells. The results showed that Ox. sol. fr. was composed mainly of pectin polysaccharides while 4K sol. fr. was composed both of pectin and hemicellulosic polysaccharides. The evidence that higher percentage of acid sugar and higher concentrations of hydrocinnamic acids were present in 4K sol. fr. of non-elongtated cell walls suggests that more pectic polysaccharides are cross-linked with other polymers in non-elongated walls. A higher digestibility of elongated cell-walls suggests that xyloglucan in the walls are easy to creep by cellulase or expansin while the non-elongated cell-walls show a cellulase-resistant property due to the cross-links between polysaccharides such as pectin and xyloglucan. The facts suggest that ferulic acids are not only ester-linked to pectic polysaccharides but also hemicellulose polysaccharides. These esterified hydroxycinamic acids may form complex cross-links between pectins, xyloglucans, or pectin and xyloglucan, therefore, involving in the cessation of cell elongation of suspension-cultured cells of Mentha.