pH与盐度胁迫对鼠尾藻光合作用及抗氧化系统的影响

为研究鼠尾藻(Sargassum thunbergii)在逆境胁迫条件下光合作用能力的变化及抗氧化系统的调节机理,利用液相氧电极技术和抗氧化酶试剂盒,检测了pH、盐度胁迫对鼠尾藻表观光合作用、色素含量、丙二醛(MDA)含量及抗氧化酶活性的影响。结果表明:(1)pH 6.0与pH9.5胁迫处理24 h后鼠尾藻表观光合速率均大幅下降,48 h后均与对照组(pH 8.5)差异显著(P0.05);(2)pH 9.5胁迫处理48 h后SOD、CAT活性均显著升高(P0.05),MDA含量呈先上升后下降趋势;(3)盐度15胁迫处理24 h,盐度20与25胁迫处理48 h后表观光合速率显著低于对照组(盐度31,P0.05),胁迫72 h后3个处理组表观光合速率有一定幅度的上升;(4)盐度20胁迫处理24 h后MDA含量先上升后下降(P0.05),SOD、CAT活性由24 h至48 h时有一定幅度的上升。盐度15胁迫处理72 h后MDA显著上升(P0.05),而SOD、CAT活性较低。可以得出pH胁迫使鼠尾藻光合作用能力降低,强碱性使藻体受到活性氧损伤。盐度为15时,鼠尾藻抗氧化酶活力较低,当高于15时,抗氧化系统对活性氧有较高的清除能力。

Effects of pH and salinity stress on photosynthesis and antioxidant system of Sargassum thunbergii

In this study, a liquid-phase oxygen electrode system and an antioxidant enzymes kit were used to determine the photosynthetic characteristics and antioxidant system of Sargassum thunbergii at various pH and salinities. The net photosynthetic rates (Pn), pigment content, maleic dialdehyde (MDA) content and antioxidant enzymes activity of S. thunbergii were investigated. The major results included: (1) Pn rapidly decreased at pH 6.0 and pH 9.5 for 24 h, which were remarkably significantly (P<0.05) compared with that of the control (pH 8.5) after 48 h. (2) Both Superoxide dismutase (SOD) and Catalase (CAT) activity increased significantly (P<0.05) at pH 9.5 after 48 h. And MDA content firstly increased then decreased at pH 9.5 after 48 h. compared with that of control (salinity 31), Pn decreased significantly (P<0.05) at salinity 15 after 24 h and at salinity 25 or salinity 20 after 48 h. However, Pn had some rise at salinity 25, 20 and 15 after 72h. (4) MDA content increased significantly (P<0.05) at first 24 h and then rapidly decreased at salinity 20. And both SOD and CAT activity increased significantly (P<0.05) at salinity 20 from 24 h to 48 h. MDA content increased significantly (P<0.05) with SOD, CAT activity relatively low at salinity 15 after 72 h. Above results indicated that photosynthetic capacity of S. thunbergii was inhibited at pH 6.0 and pH 9.5. S. thunbergii was damaged by reactive oxygen species (ROS) under strong alkaline stress. Antioxidant enzymes eliminated ROS readily at salinity over 15 but had low activity at salinity 15. In a word, these results revealed the change of photosynthetic capacity and provided reference for the regulating mechanism of antioxidant system response under adversity stress.