Cu和Cd联合胁迫对海草泰来藻光合作用的影响

Effects of coupled stress of copper and cadmium on the photosynthesis of seagrass Thalassia hemprichii

利用叶绿素荧光技术研究了重金属Cu和Cd联合胁迫对热带海草泰来藻(Thalas-sia hemprichii)光合作用的影响。结果表明:Cd与较高浓度Cu(1.0mg·L-1)的联合胁迫均使荧光参数——最大光量子产量(Fv/Fm)、光化学猝灭系数(qP)及非光化学猝灭系数(NPQ)显著降低,且海草于暴露5d后死亡,表明在Cd与较高浓度Cu的联合胁迫下泰来藻的光合作用遭受严重破坏,光保护机制丧失;而Cd与较低浓度Cu(0.1mg·L-1)的联合胁迫5d后使qP和NPQ反而有所上升,并且在恢复期,Fv/Fm可恢复至暴露前的水平,表明Cd与较低浓度Cu的联合胁迫可激发泰来藻的光保护机制。另外,在Cu和Cd的联合胁迫下,海草叶片色素含量均表现出随Cd浓度的上升而增加的趋势,表明在复合胁迫下,仅用叶绿素等色素含量判断海草受胁迫程度存在不准确性,需要结合其他指标做进一步的分析。

By using chlorophyll fluorescence technique, this paper investigated the photosynthetic parameters of seagrass Thalassia hemprichii under the coupled stress of Cu and Cd. Under the stress of Cd plus higher concentration （1.0 mg L-l ） Cu, the maximum quantum yields （Fv/ Fm）, photochemical quenching （qP）, and non-photochemical quenching （NPQ） declined remarkably, and the seagrass died after 5 days exposure, indicating that the photosynthesis of T. hemprichii suffered from severe damage, and the photo-protective mechanisms lost. On the contrary, after 5 days coupled stress of Cd and lower concentration （0.1 mg L-x） Cu, the qP and NPQ had somewhat increase, and the Fv/Fm recovered to the pre-exposure level during re- covery period, suggesting that the photo-protective mechanisms of T. hemprichii could be pro- voked and enhanced under the coupled stress of Cd and lower concentration Cu. In addition, un- der the coupled stress of Cu and Cd, the pigment content of the seagrass increased with increas- ing concentration Cd, suggesting that simply using pigment content to assess the stressed level of seagrass was inaccurate, and other indices and further analysis were needed.