The binding of Al in different polysaccharides alleviates Al toxicity to root apices

Roles of mucilage in protection of root apices from Al toxicity are studied by the comparison of Al binding in different polysaccharides of mucilage and root Al uptake in solution with exogenous pectin and dextran as well as root growth and Al uptake with/without mucilage under mist culture. The results indicate root apices removed of mucilage have higher content of Al and lower root elongation rates. Size exclusion chromatography shows: two peaks of polysaccharides are overlapped by Al content and higher content of Al is found in the fraction of high molecular weight, Al binding enlarges the molecular weight of polysaccharides, thus indicated that Al is bound in polysaccharide especially in high molecular weight fraction. Exogenous pectin is more effectively reduced Al uptake in root apices than dextran and shows a dose dependent manner. These results indicated that polysaccharides with high molecular weight (e.g. pectin) might be more effective in immobilizing Al as well as reducing Al uptake in root apices.