The sugarcane variety,YT55,was used as experimental material to investigate the effects of magnesium (Mg) on ameliorating aluminum (Al) rhizotoxicity in sugarcane.The hydroponic experiment was carried out and the changes of relative root elongation rate and antioxidant enzyme activity were examined.The results revealed that root elongation was strongly inhibited in the presence of 50 and 100 μ mol/L Al in a simple Ca solution at 24 h,and the inhibition was ameliorated over stress time.Significant amelioration of Al rhizotoxicity on root elongation was detected when the solutions contained 2 mmol/L Mg.After 24 h,73％ and 113％ increases were detected for the relative root elongation rates at two levels of Al treatment adding Mg when compared with Al treatments,respectively.The activities of GPX,SOD and APX in sugarcane roots increased after 24 h.Then the activities of SOD,GPX and APX decreased at 48 h and slightly increased at 72 h.Application of 2 mmol/L Mg in Al solution resulted in increase of the GPX activity of 50 μ mol/L Al treatment,SOD and APX activities of 100 μmol/L Al treatment after 24 h stresses.The activities of three antioxidant enzymes maintain higher level than those of Al treatment at 48 h and 72 h.These results revealed that increase of antioxidant enzyme activities play important role in alleviating Al toxicity by magnesium.%为了明确镁铝互作对甘蔗根系的影响,以甘蔗品种YT55为材料,通过简单钙溶液培养的方法,分析在不同浓度铝、镁处理下,甘蔗根的相对伸长率、抗氧化酶GPX、SOD和APX活性的变化.结果显示:50和100 μmol/L铝处理24 h,根系的伸长受到严重抑制,根的相对伸长率下降,但是随着胁迫时间的延长,铝毒对根伸长的抑制减弱;添加2 mmol/L的MgSO4到铝处理液中,3个时间点添加镁处理的根相对伸长率均高于没有添加镁的处理,镁缓解了铝毒对根伸长的抑制.铝胁迫24 h,铝处理的根系GPX、SOD和APX酶活性显著提高,但是随着处理时间的延长,在48 h表现为下降,72 h略微上升.铝胁迫24 h,镁处理与没有镁的处理相比,在50 μmol/L铝处理下的GPX酶活性,100 μmol/L铝处理下SOD和APX酶活性显著提高.到胁迫48 h,3个酶活性并未出现下降,高于没有添加镁的处理,72h仍保持较高活性但与添加镁的处理没有显著差异.由此可见,甘蔗短时间内提高根系抗氧化酶活性在镁缓解甘蔗铝毒中起重要作用.
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