Changes of major wall polysaccharides and glycoproteins of tobacco cells in response to excess boron

Effects of excess concentrations of boron on major cell wall components of tobacco cells(Nicotiana tabacum L. cv. Burley 21) were studied. Pectin, xyloglucan, hydroxyproline-richglycoproteins (extensin), and arabinogalactan proteins were characterized. Results showedthat increased boron supply resulted in significant decrease in cell and cell wall dry weights.Also, high concentrations of boron reduced relative amounts of major wall components.Compared with the normal conditions, increase in certain sugars in pectin (e.g., xylose andits methylated derivative) and decrease in glucose, arabinose, and rhamnose in those treatedcells with higher concentrations of boron was significant. The content of hydroxyprolinerichglycoproteins decreased when tobacco cells were supplied with higher concentrations ofboron. In these cells, increased ratio of protein to glycan part and increase in hydroxyl lysineamong other amino acids were noticeable. Amount of arabinogalactan proteins also decreasedas boron supply increased. Excess boron did not alter the composition and concentration ofamino acids of arabinogalactan; however, it remarkably increased xylose and glucose butdecreased galactose and arabinose concentrations.