The Pore Size of Non-Graminaceous Plant Cell Walls Is Rapidly Decreased by Borate Ester Cross-Linking of the Pectic Polysaccharide Rhamnogalacturonan II

The walls of suspension-cultured Chenopodium album L. cells grown continually for more than 1 year on B-deficient medium contained monomeric rhamnogalacturonan II (mRG-II) but not the borate ester cross-linked RG II dimer (dRG-II-B). The walls of these cells had an increased size limit for dextran permeation, which is a measure of wall pore size. Adding boric acid to growing B-deficient cells resulted in B binding to the wall, the formation of dRG-II-B from mRG-II, and a reduction in wall pore size within 10 min. The wall pore size of denatured B-grown cells was increased by treatment at pH