Response Of Submerged Plant Vallisneria Spinulosa To Changes Of Heavy Copper And Water Level In Po Yang Lake

Poyang Lake is located in the north of Jiangxi Province,which in the south bank of the middle Yangtze River.It is the largest freshwater lake in China.Due to the rapid economic development,human and natural factors,the water quality of Poyang Lake has deteriorated significantly.And the low water level advanced and the dry period prolonged.At the same time,a large number of municipal domestic sewage,industrial and agricultural wastewater were collected by the rivers entering the lake.The high level of heavy metals was imported into the Poyang Lake,which led deterioration of the water quality,and resulted in copper ion pollution.Therefore,it is great theoretical and practical significance for the protection of submerged plants,and the restoration of water bodies by studied the interaction between copper and water depth changes on the growth of Vallisneria spinulosa.In this paper,a dominant species of submerged plants in Poyang Lake,Vallisneria spinulosa,was taken as the research object.It’s growth and physiological response to the interaction of water depth gradient and heavy copper were discussed.(1)In experiment 1,with the increase of low water level(1.5m water depth group compared with 1.0m group and 0.6m group respectively),the leaves of Vallisneria spinulosa were broken and rotted,and the leaf weight and plant height decreased.While the biomass on the Vallisneria spinulosa decreased,the new roots in the underground part increased,and the stolons were strong,which facilitated the Vallisneria spinulosa to absorb more nutrients through the roots.The stolons in deep water are thinner and longer than those in simulated early low water level,which is due to the avoidance of low light shading conditions in deep water.(2)The more the water level drops,the more obvious the sexual reproduction of Vallisneria spinulosa turns into asexual reproduction.The shallower the water level rises,the less the number of blossoms,the more the number of underground winter buds.The weight of winter buds in 1.5m to 0.3m group increases most obviously than other groups.The environment of unsuitable growth can be passed through the balanced coordination of asexual reproduction and sexual reproduction.(3)In experiment 2,the period was 29 days.At the 5th day of sampling,thesoluble protein content,POD and SOD specific activity reached the maximum at the concentration of 150 mg kg-1,while the chlorophyll content of Vallisneria spinulosa significantly decreased under the action of copper ions.However,on the 12 th day of sampling,water depth and Cu2 + stress were more obvious.With the deepening of water depth,the maximum point of chlorophyll,soluble protein and POD moved forward to the lower Cu2+ concentration group at the 5th day of sampling.(4)Under certain conditions of copper ion and water depth,the chlorophyll content of Vallisneria spinolosa decreased first and then increased with time.SOD,soluble protein and POD increased significantly on the 5th day,then gradually returned to normal level.SOD reflected the water depth gradient earlier than other antioxidant enzymes.Therefore,compared with the general plant stress research,SOD is more time-sensitive than activity index to measure the environmental stress degree of Vallisneria spinulosa.(5)In the process of repairing copper ions in water body,the early water depth will aggravate the chlorosis and wilting of Vallisneria spinolosa under copper ions,and the content of antioxidant enzymes in plants will also increase significantly under the influence of water depth.However,when the concentration of copper ion is not more than 150 mg kg-1,the effect of water depth on Vallisneria spinulosa is within 1.5m water depth.With its adaptation to environmental stress,the leaf color of Vallisneria spinulosa will be darker and the plant height will be higher.As an important tool for aquatic ecological remediation,submerged plants are inexpensive and environmentally polluting,which can not be achieved by other physicochemical means.The rapid deterioration of water environment leads to the sharp decline of submerged plants in the environment where the water level of Poyang Lake fluctuates sharply and heavy metal pollution is aggravating.Water remediation and submerged plants are closely related,so we should also consider their background values when we restore water,and choose the most suitable remediation scheme for submerged plant population.This study provides a theoretical basis for future water restoration and submerged plant protection.