Effects Of Hg And Cd Stress On The Physiological And Biochemical Characteristics Of Halophila Ovalis

Halophila ovalis is a monocotyledonous plant grown in the subtropical and shallow seas.It is a dominant species for the subtropical seagrass community in China and forms seaweed beds in the coastal or dotted form.Seagrass bed is one of the three major marine ecosystems in the coastal area,with important ecological functions and values.But recently,due to serious pollution of the marine environment,seaweed living environment has been destroyed,the global seaweed had serious degradation.The pollution of marine heavy metal have traceability,prolonged halflife,enrichment and other characteristics,causing poisoning of marine life.The stress of heavy metals in freshwater submerged plants has been reported in some water bodies,but the stress of heavy metals on seagrass is almost no research.In this paper,chlorophyll a,chlorophyll b,carotenoids,malondialdehyde,superoxide anion,lipoxygenase,superoxide dismutase,peroxidase and superoxide dismutase were measured under Hg and Cd stress,and the change of toxicase was discussed.The toxicity of heavy metals to seagrass was analyzed,and the following conclusions were drawn:1.Effects of Hg and Cd on Photosynthetic Pigment ofHalophila ovalis.The chlorophyll content of Halophila ovalis can be reduced by promoting chlorophyll biosynthesis,but the chloroplast membrane and thylakoid membrane in the leaves of Prunus armeniaca were destroyed under long-term stress,and the activity of chlorophyll synthesis was necessary was inhibited,causing a substantial reduction in chlorophyll content,resulting of leaf loss of green plants decline.Carotenoids in addition to the auxiliary pigments involved in photosynthesis,but also has the function of scavenging reactive oxygen species,under heavy metal stress,the growth and utilization of carotenoids increased by the synthesis of carotenoids to enhance the capture and removal of reactive oxygen species.2.Effects of Hg and Cd on Membrane Lipid of Halophila ovalis.Heavy metals promote the production of reactive oxygen species in a large amount of Halophila ovalis,and oxidize the unsaturated fatty acids in the cell membrane by reactive oxygen species,and form the final product malondialdehyde under the catalysis of lipoxygenase.Malondialdehyde can further aggravate the damage of membrane,and caused the death of the plant.3.Response of Antioxidant Enzymes of Hippophae rhamnoides L.under the stress of Hg and Cd.Due to heavy metals lead to a large number of reactive oxygen species in the body of theHalophila ovalis,the body through regulating the activities of SOD,CAT and POD to improve the activity of oxygen and repair oxygen damage,but with the stress of long-term and high concentrations,reactive oxygen production and removal of dynamic balance is broken,active oxygen accumulation in the body,the body caused by poison,metabolic disorders in the body,antioxidant enzyme activity decreased,and final plant is die.In summary,the heavy metals Hg,Cd by forcing the large amount of reactive oxygen species,and induced antioxidant enzyme activity increased to remove reactive oxygen species and repair oxygen damage.Active oxygen in the accumulation process can destroy the cell membrane,resulting in increased membrane permeability,the external heavy metals easier to enter the body,and a large number of material loss,metabolic disorders.Reactive oxygen also destroyed the structure of chloroplast membrane and thylakoid membrane,casuing the content of photosynthetic pigment decreased,and the photosynthesis was seriously blocked,resulting in decreased physiological activity of leaves of salt grass,leaves pale yellow fade,gradually decline.The results indicated that marine heavy metals could be poisoned by the physiological and biochemical characteristics of seaweed,and heavy metal pollution could be one of the important factors leading to seaweed bed decay.