Effects of iron and manganese plaques on aluminum uptake and translocation by rice seedlings

A hydroponic experiment was conducted to investigate the influence of iron and manganese plaque on Al uptake and accumulation of Feiyouduoxi No.1 (Al-resistant rice cultivar) and Hongliangyou 166 (Al-sensitive rice cultivar).The formation of iron plaque,manganese plaque and iron/manganese plaque was induced by exposing the rice roots to 0.8 mol·L-1 Fe2+ or Mn2+,and the quantity of iron plaque was much more than that of manganese plaque.Most Fe was found in mixture of iron/manganese plaque,while Mn was much less and only accounted for 0.12%-0.20% of the total.Relative root elongation rate of rice seedlings under Al toxicity showed the following rank order:manganese plaqueiron/manganese plaqueiron plaqueno plaque.Al contents and accumulation in whole rice seedlings showed the following rank order:root surface with plaquerootshoot.Ninety-one percent and eighty-five percent of Al was present in the root surface plaque of Al-tolerant Feiyouduoxi No.1 and Al-sensitive Hongliangyou 166,respectively,indicating that Al-resistant cultivar was more efficient to exclude Al from root and reduce the translocation of Al from root to shoot.Manganese plaque exerted more pronounced effect in Al tolerance.