镉对龙葵幼苗生长和生理指标的影响

采用营养液培养法研究了镉胁迫条件下龙葵幼苗生长、生理响应及镉积累特性。结果表明，镉胁迫下，龙葵幼苗生长受到一定程度的抑制，并且具有浓度效应和时间效应。镉胁迫还导致龙葵叶片色素含量下降。叶绿素a、b和类胡萝卜素平均含量在高浓度镉（150μmol·L^-1）处理条件下分别较对照降低55．5％、63．9％和43．3％。低浓度镉（25μmol·L^-1）处理15d内显著促进龙葵幼苗根系活力，平均根系活力较对照上升10．4％，而高浓度镉处理下，根系活力呈现先升后降的趋势，镉处理10d之后达到峰值；随着镉浓度的升高和胁迫时间的延长，龙葵幼苗叶片相对电导率、丙二醛（MDA）含量和渗透调节物质均呈现显著上升趋势。相对于对照植株，低浓度镉处理下龙葵叶片平均相对电导率、MDA含量、可溶性糖和脯氨酸含量上升17．7％、117．7％、5．6％和95．3％，而高浓度镉处理下上升幅度更大，分别为39．0％、194．6％、56．3％和758．0％。从积累部位来看，镉主要积累在龙葵幼苗地上部，镉含量由高到低依次为叶片〉茎〉根系，高浓度镉胁迫20d之后根茎叶镉含量为5d时的1．73、1．49和1．40倍，分别为1287．25、1718．14和2385．27μg·g^-1DW。

Physiological Responses of Solanum nigrum L. Seedlings to Cadmium Stress

Physiological responses and cadmium （Cd） accumulation in Solanumnigrum L. seedlings under Cd stress were investigated by nutrient solution culture method. The results showed that Cd could affect the growth of Solarium nigrum L. seedlings, and had concentration-dependent and time-dependent effects. Cd stress also ted to the decrease of leaf pigments contents. Average contents of Chlorophyll a（Chla）, Chlorophyll b（Chlb）and carotenoid （Car）decreased 55.5%, 63.9% and 43.3% when Solanum nigrum L. seedlings subjected to high concentration of Cd （ 150 μmol·L^-1）. Furthermore, low Cd （25 μmol·L^-1） improved root activities of Solarium nigrum L. seedlings significantly, and increased 10.4% compared to the control plants; Under high concentration of Cd, root activities of Solarium nigrum L. seedlings increased firstly and decreased, the submit was found after 10 d of Cd treatment. The relative elective conductivities, malondialdehyde（MDA）contents, soluble sugar contents and proline contents increased with increasing Cd concentration in the solution and along with treatment time; Com- pared to the control plants, they increased 17.7%, 117.7%, 5.6% and 95.3% under low Cd stress, and increased 39.0%, 194.6%, 56.3% and 758.0% under high Cd stress. Cd mainly accumulated in the shoot of Solanum nigrum L. seedlings, and Cd concentration in the plant tissues could be drawn as followed：leaf〉stem〉root, the maximum were detected after 20 d of high Cd stress, 1 287.25, 1 718.14 and 2 385.27μg·g^-1DW of Cd concentrations in the root, stem and leaf, respectively.