水蕴草对Pb的积累及其耐性机制

研究了Pb在水蕴草中的积累、亚细胞分布和赋存形态,以期揭示水蕴草对Pb的耐性机制。结果表明,在9 d的水培实验中,水蕴草对Pb的富集量随着Pb处理浓度的升高而增加,最大可富集103.55 mg/g DW,可以修复较高Pb污染( 细胞器与膜 > 可溶性部分,其中细胞壁是Pb的主要贮存部位。采用化学试剂逐步提取法分析Pb存在的化学形态表明,水蕴草体内的Pb主要以盐酸提取态为主,其次为醋酸和氯化钠提取态,其他Pb提取态的含量则较少。而细胞壁中Pb的赋存形态主要以盐酸提取态和醋酸提取态为主,细胞器和膜中的Pb主要以氯化钠和醋酸提取态为主。综上表明,水蕴草主要通过将Pb与草酸盐和磷酸盐相结合,从而将其束缚在细胞壁中,限制了Pb进入细胞内部,从而减轻了Pb对水蕴草的毒害,增强了水蕴草对Pb的耐性。

Accumulation of lead in Elodea densa (Planch.) Casp. and its tolerance mechanism to lead

The accumulation,subcellular distribution and chemical forms of lead (Pb) in Elodea densa (Planch.) Casp. were investigated in order to determine the mechanisms involved in Pb tolerance. We found that the accumulation of Pb in Elodea densa (Planch.) Casp. increased along with the rise of Pb in sulution under different Pb solution for 9 days. Elodea densa (Planch.) Casp. could accumulate of Pb with a maximum of 103.55 mg/g (dry weight) after being exposed to 100 mg/L Pb,which enabled it to repair a higher contaminated water of Pb(Eodea densa (Planch.) Casp. decreased as the following pattern: cell wall>cell organelle and membrane>soluble fraction,among which indicating that cell wall was apparently the major storage of site for Pb in the plant. Through the sequential chemical extraction method, we also determined that the Pb in Eodea densa (Planch.) Casp. was proved to be mainly most existing soluble in the extration of HCl, followed by HAc and NaCl, others being the least. Moreover, the chemical forms of Pb were chiefly HCl- and HAc-extractable forms in the cell wall, whereas NaCl- and HAc-extractable forms were recovered from cell organelles and membranes. Thus, we determined that when combined with other compounds, which including oxalate and phosphate, the Pb of Elodea densa (Planch.) Casp. was prevented from moving within the cell, and was instead bound to the cell wall, which, as a result, diminished the potential of the Pb toxicity and increased the plant's tolerance.