Comparison of aluminum accumulation ability of cell wall polysaccharides in Oryza sativa and Triticum aestivum root tips under aluminum toxicity

Hydroponics were used to compare eight genotypes of four Poaceae plants (Oryza sativa L., Zea mays L., Sorghum bicolor (L.) Moench, and Triticum aestivum L.). We investigated their resistance to aluminum (Al) and analyzed the polysaccharide components of the cell wall after Al accumulation. Results revealed that under 5-200 μmol/L Al treatment, rice exhibited the strongest Al resistance, whereas wheat demonstrated the weakest, thus further experiments were carried out on rice and wheat. Under 50 μmol/L Al treatment, the content of pectin and hemicellulose 1 was higher in the wheat root tips than that in the rice root tips. Furthermore, Al content in the cell wall of ‘Nipponbare’ and ‘Zhefu 802’ seedlings accounted for 78.7% and 91.6% of that in the root tips, and in ‘Yangmai 18’ and ‘Yangmai 16’ seedlings accounted for 64.9% and 72.1% of that in the root tips. The Al adsorption-desorption tests further showed that Al uptake in the wheat root tip cell wall was higher than that for rice, whereas the desorption rate was lower than that for rice. The cell wall was the main site for Al accumulation, the pectin component in the cell wall was the major binding site of Al-sensitive rice and wheat genotypes, and the hemicellulose 1 component was the major binding site of Al-tolerant rice and wheat genotypes.