Abstract:

【Objective】 Root border cells are released from root apices of most plant species, and the root tip is the target of A1 toxicity, thus it was presumed that border cells might be more sensitive to A1 toxicity than root cells. The objective of the present study is therefore to investigate the differences in cell wall polysaccharides between border cells and root apices of pea (Pisum sativum) under A1 exposure. 【Method】 The root border cells of pea (Pisum sativum) were cultivated by mist containing different levels of Al in 24°C growth chamber for 24 h after seed soaking. 【Result】 Results showed that the viability of border cells was significantly decreased by the 4.0 mmol?L-1AlCl3 treatment, and the inhibitory rate of the viability of border cells was 19.2％and the inhibitory rate of relative root elongation was 10.1% after 24 h treatment of 4.0 mmol?L-1AlCl3. The uronic acid and sugar contents of pectin and cellulose in border cell walls were significantly (P＜0.05) higher than in the root segments of 0-10 mm and 10-20 mm at the absence of Al. The uronic acid content of pectin in border cell walls increased obviously related to the root segments of 0-10 mm and 10-20 mm at 4.0 mmol?L-1 A1C13. The sugar content of pectin in border cell walls was increased significantly (P＜0.05), but decreased seriously in hemi-cellulose and cellulose at 4.0 mmol?L-1A1C13. The Al content of pectin, hemi-cellulose and cellulose in the border cell walls were significantly (P＜0.05) higher than in the root segments of 0-10 mm and 10-20 mm. Al contents of pectin 1 in the border cell walls were 14.4 and 17.4 fold to that in the root segments of 0-10 mm and 10-20 mm at 4.0 mmol?L-1 A1C13, respectively, and the Al content in the root segments of 0-10 mm was higher than in the 10-20 mm; at the same time,. hemi-cellulose and cellulose, the major compositions of cell wall, contained more Al than pectin. 【Conclusion】 These results indicated that the contents of Al binding to cell walls is related to the contents of pectin in cell walls and the border cells were more sensitive to Al than the root segments of 0-10 mm and 10-20 mm. Cell wall polysaccharides including pectin, hemi-cellulose and cellulose might play important roles in binding Al in border cell walls.

Key words: pea (Pisum sativum), border cells, al toxicity, cell wall polysaccharides, sensitivity