Hg-Cd复合胁迫对卵叶喜盐草光合色素和丙二醛含量及抗氧化酶活性的影响

摘要

通过胁迫试验研究Hg-Cd复合胁迫对卵叶喜盐草光合色素含量、丙二醛(MDA)含量及抗氧化酶活性的影响.结果表明,Hg-Cd复合毒性对卵叶喜盐草叶绿素a、叶绿素b和类胡萝含量显著影响(P<0.05),当Hg、Cd质量浓度分别大于0.005和0.100 mg·L-1时,叶绿素a、b比值,叶绿素a和类胡萝卜素含量下降,光合作用受抑制;Hg-Cd复合胁迫对卵叶喜盐草的MDA含量影响有统计学意义(P<0.05),当Hg、Cd质量浓度分别为0.005和0.100 mg·L-1时,MDA含量上升41.5%;Hg、Cd复合胁迫对卵叶喜盐草的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性影响有统计学意义(P<0.05),SOD活性随浓度梯度逐渐下降,在Hg、Cd质量浓度分别大于0.010和0.200 mg·L-1时,SOD活性降低,POD和CAT活性随胁迫浓度梯度呈先增后减趋势,其中当Hg、Cd质量浓度分别为0.010和0.20 mg·L-1时,而POD和CAT活性均上升为最大值,分别较对照组增加12.35%和22.75%,当Hg、Cd质量浓度分别大于0.015和0.300 mg·L-1时,POD和CAT活性开始下降至最低.总的来说,Hg、Cd联合胁迫的浓度大于0.005和0.100 mg·L-1时,卵叶喜盐草光合色素含量下降,MDA含量和抗氧化酶活性均相应发生变化.%Halophila ovalis is one main kind species of seagrass beds in coastal sea of South China. This study tried to explain the effects of Hg-Cd combined stress on the photosynthetic pigment content, malondialdehyde (MDA) content and the activities of SOD, POD and CAT of Halophila ovalis. The results showed that Hg-Cd combined stress had significant effect on the contents of chlorophyll a, chlorophyll b and carotenoid in the leaves of Halophila ovalis (P <0.05). When the combined concentration of Hg-Cd was more than 0.005 and 0.100 mg·L-1 (P <0.05), with concentration of Hg-Cd increment, the content of chlorophyll a and b was significantly decreased, and the photosynthesis of Halophila ovalis was inhibited. The content of MDA was increased by 41.5% when the concentration of Hg-Cd stress was 0.005 and 0.100 mg·L-1, respectively. The effects of Hg-Cd also had significant stress on the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (P <0.05). The activity of SOD decreased with the concentration gradient increasing. The activity of SOD was significantly decreased when the combined concentration of Hg-Cd was more than 0.01 and 0.2 mg·L-1, respectively. The activity of POD and CAT increased to the maximum after the concentration of Hg-Cd was more than 0.010 and 0.200 mg·L-1, respectively, which was 12.4% higher than that of the control group 22.8%. When the combined concentration of Hg-Cd was more than 0.015 and 0.300 mg·L-1, POD and CAT activities began to decline, and to the lowest at last. In general, the concentration of Hg-Cd combined stress was more than 0.005 and 0.100 mg·L-1, which resulted in decrease of photosynthetic content and antioxidant enzyme activity of Halophila ovalis.