孔雀草对镉胁迫的响应及其积累与分布特征

Cd stress,accumulation and distribution characteristics in Tagetes patula L.

采用营养液培养法研究了不同浓度的Cd(0、0.01、0.05、0.1、0.2、0.3、0.4 mmol·L-1)对孔雀草叶片光合色素和丙二醛含量以及Cd积累量、亚细胞与化学形态分布的影响.结果表明,随着营养液Cd浓度的增加,叶片光合色素含量呈先升后降趋势,丙二醛含量则呈线性递增趋势,高浓度Cd处理(≥0.1 mmol·L-1)对孔雀草产生了显著的胁迫响应.Cd主要贮存于可溶组分中,根系中占50.91%—66.40%,叶片中占39.09%—60.52%;其次为细胞壁,细胞器中的镉比例较低.随着Cd处理浓度的增加,Cd在根系细胞壁中的贮存比例呈增加趋势.液胞区隔化和细胞壁固持是孔雀草应对Cd胁迫的重要耐性机制.根系中的Cd主要以乙醇提取态存在,占27.62%—70.46%,叶片中Cd主要以去离子水提取态和氯化钠提取态存在,两者合计占58.91%—71.09%.叶片中活性态Cd含量显著低于根系,显著降低了地上部Cd的积累,也显著降低了Cd对地上部的胁迫作用.

A nutrient solution cultivation experiment was conducted to investigate the effects of different Cd doses（ 0,0. 01,0. 05,0. 1,0. 2,0. 3,0. 4 mmol·L- 1） on photosynthetic pigment and malondialdehyde（ MDA） contents in leaves of Tagetes patula L,and analyzed the Cd accumulation,subcellular distribution and chemical form in the plant. The results showed a parabolic relationship between the photosynthetic pigment contents and Cd doses,while the MDA contents showed a linear increasing trend. As such,high Cd treatments（ ≥ 0. 1 mmol·L- 1） induced significant stress responses in Tagetes patula L. The majority of Cd was stored in the soluble fractions（ 50. 91% —66. 40% for roots and 39. 09% —60. 52% for leaves）,followed by the cell wall fractions,and a trace amount of Cd were found in the organelle fraction. The Cd concentrations in cell walls increased with elevating Cd supply. Therefore,the vacuolar compartmentalization and cell wall binding may be the main tolerance mechanisms to Cd in Tagetes patula L. As to Cd chemical forms,a large quantity of Cd existed as ethanol-extractable forms in roots（ 27. 62% —70. 46%）,while most of Cd was stored as d—H2O— and Na Cl-extractable fractions in the shoots（ 58. 91% —71. 09%）. The quantity of active Cd in the leaves was much lower than that in the roots,which contributed to the reduction of Cd toxicity in the shoots,but it also decreased Cd accumulation capacity in the shoots.