锰胁迫下龙葵和小飞蓬根叶中植物螯合肽和类金属硫蛋白的变化

采用溶液培养的方式研究不同锰浓度(0.005,2,4,8,16mmo.lL-1)胁迫下龙葵和小飞蓬的根和叶中的植物螯合肽(PCs)和类金属硫蛋白(MTLP)的诱导合成量.结果显示,随着锰浓度的升高,两种植物的株高和根长先略高于对照,而后逐渐下降.锰胁迫诱导植物产生的PCs有先上升后下降的趋势,但含量较少;而PCs产生的前体物质谷胱甘肽(GSH)和MTLP的诱导量与锰浓度之间存在一定相关性,随着锰浓度增加呈现先上升后下降的规律.两者的非蛋白巯基化合物(TNP-SH)和GSH在8mmol·L-1锰浓度下达到最大值,总体上龙葵的含量比小飞蓬大.MTLP的含量随着锰浓度的升高呈先上升后下降的趋势,龙葵在8mmol·L-1锰浓度时含量最高,而小飞蓬叶和根分别在2mmol·L-1和4mmo.lL-1时即达到最大,之后下降,且龙葵的MTLP含量大于相应浓度下的小飞蓬的含量.实验表明GSH和MTLP对不同锰处理浓度的响应都较敏感,故可作为植物耐锰胁迫及鉴定土壤锰污染的参考指标.随着Mn处理浓度增大,龙葵受Mn胁迫的影响比小飞蓬小,说明其耐Mn水平较小飞蓬高,更适合用于Mn污染地区的植物修复.

Phytochelatins and metallothionein-like proteins in Solanum nigrum L. and Conyza canadensis L. roots and leaves under Mn stress

Phytochelatins (PCs) and Metallothionein-like proteins (MTLP) have been suggested as two potential biomarkers for evaluating metal phytoxicity. However,no research has reported that these two compounds exist in plants under Mn stress. This study aimed to investigate the correlations between Mn toxicity and production of PCs and MTLPs in Solanum nigrum L. and Conyza canadensis L. after 30 days exposure to Mn²⁺ (0.005,2,4,8,16 mmol·L^-1) in hydroponic culture. Plant height and root length of both plants were first increased compared with control(0.005 mmol·L^-1)and then decreased gradually. Low contents of PCs were detected in the roots and leaves of the plants under Mn stress. The contents of Glutathione (GSH) and MTLPwere more sensitive to Mn stress,and they presented similar trends. MTLPand GSHincreased rapidly first and then dropped rapidly with the increase of Mn concentration,indicating that there were correlations between the physiochemical values and Mn concentrations in plant tissues due to the increasing supply of Mn²⁺. The contents of total non-protein SHcompounds(TNP-SH) and GSHwere significantly increased (p<0.05) in 8 mmol·L^-1 Mn²⁺ when compared to the control. The content of MTLPin S. nigrum significantly increased under 8 mmol·L^-1 Mn²⁺,while that in C. canadensis was promoted significantly under 2 and 4 mmol·L^-1 Mn²⁺. The MTLPconcentration was maintained at a higher level in S. nigrum in comparison with C. canadensis at the same Mn²⁺ concentration. GSHand MTLPcould be effective response indexes to Mn stress and identification of manganese contaminated soils. S. nigrum showed a stronger tolerance to Mn toxicity than C. canadensis,so it is more suitable for phytoremediation of Mn polluted areas.