Differences of pectin content and methylation in root cell wall of pea(Pisum sativum) cultivars with different Al tolerance

【Objectives】 The study investigated the relationship between changes of cell wall pectin, pectin methyl esterification degree and aluminum tolerance in different cultivars of pea (Pisum sativum) to provide theoretical evidences how genetic differences affected aluminum tolerance during plant growth. 【Methods】 All cultivars were cultivated by mist under 24℃growth chamber for 24 h after seed soaking. The root was divided into three segments: 0-2.5 mm, 2.5-5.0 mm and 5.0-10.0 mm. Pectin content, methyl esterification degree and the activity of pectin methylesterase (PME) were measured in differentroot segments of cultivar Hyogo and cultivar Alaska. Relative elongation rate (RER), callose and Al content were also tested to compare Al tolerance in different root zones and cultivars of pea. 【Results】 The RER of Alaska cultivar were significantly higher than Hyogo under Al concentration of 15 μmol/L and 30 μmol/L. And, the callose and Al of 0-5 mm or 5-10 mm segments in Alaska cultivar were accumulated much less than Hyogo. This result confirmed that the Alaska was an Al resistant cultivar and Hyogo was an Al sensitive cultivar. Alaska showed lower Al contents in all segments. In the meantime, the different Al levels between two species were showed significantly in 2.5-5.0 mm and 5.0-10.0 mm segments. Uronic acid content in cell wall pectin was found decreasing sequentially from segment 0-2.5 mm to 5.0-10.0 mm in both pea species. Alaska was measured lower cell wall pectin and un-methylated pectin compared with Hyogo, especially in segment 0-2.5 mm. The activity of PME also decreased successively from segment 0-2.5 mm to 5.0-10.0 mm in both Alaska and Hyogo. The degree of pectin methylation was significantly higher in 0-2.5 mm root segment than the other root segments in Alaska. Alaska had relatively lower content of uronic acid, lower activity of PME, and higher degree of pectin methylation, especially in 0-2.5 mm root segment. 【Conclusions】The key factor for pea cultivars shows Al tolerance or Al sensitive could be pectin content and methylation level in 0-2.5 mm root segment. Hyogo is highly sensitive to Al, which contained higher pectin in 0-2.5 mm root segment. The relatively lower pectin content and high methylation, especially in 0-2.5 mm, of Alaska associated with Al tolerance characterize.