丛枝菌根真菌作用下桉树对铅的耐受机制研究

Study on the Pb-tolerance Mechanism of Eucalyptus under the Role of Arbuscular mycorrhizal Fungi

通过盆栽桉树幼苗实验,采用差速离心法和化学试剂逐步提取法,从Pb在桉树不同部位中的亚细胞分布和化学形态的角度,研究了桉树对Pb的耐受机制。结果表明Pb主要富集在桉树根部（65%-84%）,在根、茎和叶中主要分布在细胞壁组分,其次在可溶组分。接种丛枝菌根真菌（AMF）没有改变Pb在植物中亚细胞分布的格局,但在高Pb处理（200 mg/kg,400 mg/kg）时增大了根部细胞壁组分和叶片可溶组分的分配比例,说明AMF可以增强细胞壁滞留作用和液泡区隔化作用。随土壤中Pb浓度的增加,桉树根部Pb的乙醇提取态的分配比例逐渐减少,而醋酸提取态的分配比例逐渐增加,在高Pb处理时以醋酸提取态为主（40%）。高Pb处理时接种AMF,可以促使植物体内的Pb从活性较强的提取态向活性较弱的提取态转化。因此,根部固持作用、细胞壁滞留作用、液泡区隔化作用及弱活性结合态增加作用,是AMF作用下桉树耐Pb的主要机制。

The Pb-tolerance mechanism of Eucalyptus was studied by the subcellular distribution and chemical form of Pb in the different parts of Eucalyptus by the method of gradient centrifugation and sequential chemical extraction in pot experiments. The results showed that Pb accumulated mainly in root（65%-84%）, and was mainly bound to the cell wall or distributed in the soluble fraction. Arbuscular Mycorrhiza Fungi（AMF） did not change the overall pattern of subcellular distribution of Pb. However, under high Pb stress（200 mg/kg, 400 mg/kg） condition,the distributing proportions of Pb in the cell wall fraction of root and in the soluble fraction of leaf were increased. It suggested that AMF could strength the binding capacity to Pb of the cell wall in root and the vacuolar compartmentalization in leaf. With the increase in Pb concentration of soil, the ethanol-extractable form of Pb was decreased,and the HAc-extractable form was increased in root. Under high Pb stress（200 mg/kg, 400 mg/kg） condition, Pb was mainly existed as HAc-extractable form（about 40%）, and AMF inoculation could convert Pb from active forms to less-active forms. The Pb-tolerance mechanism of Eucalyptus inoculated with AMF might be due to the retention of Pb in root, binding Pb to cell wall, vacuolar compartmentalization of Pb in the soluble fraction, and increase of less-active forms of Pb.