小麦根尖细胞壁对铝的吸附/解吸特性及其与耐铝性的关系

研究了耐铝性明显差异的2个小麦基因型西矮麦1号(耐性)和辐84系(敏感)根系对铝毒胁迫的反应与根尖细胞壁组分以及细胞壁对铝的吸附和解吸的关系。结果表明,30mol/L.AlCl3可迅速抑制小麦根系伸长,但对辐84系根系伸长的抑制更为明显,且小麦根系相对伸长率随着铝浓度的提高而急剧降低。在30mol/L.AlCl3处理24h后,西矮麦1号根系伸长的抑制率为33.3%,而辐84系根系伸长的抑制率高达70.9%。小麦距根尖0～10.mm根段的铝含量和细胞壁中果胶糖醛酸含量显著高于10～20.mm根段,且前者对铝的累积吸附量明显大于后者;在0～10.mm根段,敏感基因型果胶含量高于耐性基因型,其根尖含铝量及根尖细胞壁对铝的吸附量都要大于后者。采用1.0.mol/L.NH3.H2O对细胞壁预处理2.h降低果胶甲基酯化程度后,耐性和敏感基因型根尖细胞壁对铝的累积吸附量分别降低了17.1%和20.9%,但对铝的累积解吸率没有影响。由此可见,小麦根尖是铝毒的主要位点,细胞壁果胶含量和果胶甲基酯化程度可能是导致不同小麦基因型根尖细胞壁对铝吸附量、铝积累量的差异及其对铝毒胁迫反应的差异的重要原因。

Aluminum adsorption/desorption of cell wall in root tips and its relation to Al tolerance in wheat

The response of root systems of Al-resistant(Xiaimai-1) and Al-sensitive(Fu-84) wheat(Triticum aestivum L.) genotypes to Al toxicity and the relation between root tip cell wall composition and Al adsorption/desorption by root apex cell walls were examined in this paper.Root elongation of both genotypes was markedly inhibited when wheat roots were exposed to 30 μmol/L AlCl3 solutions for 24 h,but the inhibition was more conspicuous for Fu-84.Relative root elongation rate of wheat genotypes was markedly decreased with the increasing of the Al concentration,and the inhibitory rate of root elongation was 33.3% for Xiaimai-1 and 70.9% for Fu-84 after 24 h treatment of 30 μmol/L AlCl3.In both genotypes,the content of accumulated Al,pectin uronic acid and the amount of Al adsorbed by the cell walls in 0-10 mm root segments was significantly higher than those in 10-20 mm,but the desorption rate was slightly lower in cell walls of 0-10 mm root segments than that of 10-20 mm in Fu-84,however desorption rate had no difference in Xiaimai-1 between different root segments.In 010 mm root segments,the cell wall pectin content of Fu-84 was significantly higher than that of Xiaimai-1.Al content in the root tips and the amount of Al adsorption by the root tip cell wall in Fu-84 were higher than those in Xiaimai-1.Decreasing the degree of methylation(DM) of pectin in cell walls with 1.0 mol/L NH₃·H₂O for 2 h,the total amount Al absorbed was decreased about 17.1% in Xiaimai-1 and 20.9% in Fu-84,while the effect on desorption rate was negligible.The preliminary results showed that root tip was the primary site of Al toxicity,and differences in pectin content and DM of pectin in cell wall of root tips contributed to genotypic differences in Al accumulation in root tips and thus Al resistance of wheat.