Responses Of Bermudagrass To Cadmium Stress And Its Antioxidation Under Waterlogging Conditions

As the most common heavy metal pollution and strongest toxicity,cadmium pollution has strong chemical activity in soil,with high active degree,which usually is absorbed and accumulated by plants in the form of ion,and then goes into the body and harms health through the way of the food web.The root system of lawn plants is developed,which can form a compact cover and effectively reduce soil erosion and diffusion of contaminated soil.In addition,the lawn plant has short growth cycle and high survival rate and the heavy metals in the plant could be concentrated to manage by mowing the lawn.Therefore,the use of lawn plants to restore heavy metal contaminated soil can be described as "Achieve many things at one stroke".In this experiment,Bermuda grass is as test materials,take the method of indoor planting,set up eight kinds of different treatments such as CK,50 Cd,100Cd,150 Cd,WL,50Cd+WL,100Cd+WL,150Cd+WL(the digitals represent concentration of Cd,WL represents waterlogging)which research on the effect of waterlogging,Cd single and combined stress on Bermuda grass growth(plant height,leaf length,leaf width,stem length,stem diameter and biomass),physiological and biochemical indexes(POD,CAT,SOD,MDA,chlorophyll)and enrichment ability of Bermuda grass on cadmium.The purpose of this study was to research the resistance of Bermuda grass to cadmium and defense mechanism of its antioxidant system under different management and to provide a reference for the selection of heavy metal bioremediation in the soil.The main research results are as follows:(1)Single waterlogging stress.Plant height,leaf length,stem length,stem base diameter of Bermuda grass reaching maximum,proved that waterlogging can promote stem and leaf growth of Bermuda grass to a certain extent,because the Bermuda possessed an escape strategy in face of waterlogging stress,which accelerated the growth of plants and stem segments rising longer making Bermuda grass quickly exposed above the water surface,and made the leaves of Bermuda grass fully contact with air oxygen to maintain normal photosynthesis and to avoid more harm to Bermuda grass from waterlogging environment;The belowground biomass of the Bermuda grass reached the minimum value,which indicated that waterlogging could inhibit the growth of Bermuda grass root system to some extent and may be related to low temperature and low oxygen content in the water;The activity of POD,CAT,SOD in Bermuda grass is greater than CK value,but MDA,SPAD value was lower than the CK value that Bermuda have good flooding resistance but inhibition of the synthesis of chlorophyll in a certain extent,thus affecting its photosynthesis.(2)Single Cd stress.With the increasing of Cd concentration,grass height,leaf length,leaf width,stem length,stem diameter,aboveground biomass of Bermuda grass showed a slight downward trend,which indicated that Cd can inhibit Bermuda grass growth in a certain degree but did not show significant differences,Bermuda grass can still grow normally;In the lower part of the Bermuda grass,biomass increased first and then decreased,and reached a maximum at 100 mg/L,which indicated that low cadmium stress promoted the growth of Bermuda grass roots.Activity of POD,CAT,SOD of Bermuda grass increased,MDA content decreased firstly and then increased,the Cd concentration reached the minimum value of 100 mg/L,which indicated damage of low concentration of Cd stress on Bermuda grass is not high can stimulate the activity of antioxidant enzymes to improve self-healing effect;The SPAD value of Bermuda grass showed a decreasing trend,which indicated that Cd could affect the synthesis of chlorophyll in Bermuda grass.(3)Combined stress of waterlogging and Cd.With the increasing of Cd concentration,height,leaf length,leaf width,stem length,stem diameter,aboveground biomass and SPAD values of Bermuda grass showed a slight downward trend,which indicated under composite stress could inhibit the growth and synthesis of chlorophyll in Bermuda grass;POD,CAT and SOD of Bermuda grass showed different trends,respectively at the concentration of Cd up to the maximum of 150,100,50 mg/L,MDA content reached the maximum value of 100 mg/L in Cd concentration,which indicated different antioxidant enzymes play a dominant role in different concentrations of Cd,and their mutual coordination kept the plants from harm;When the concentration of Cd was 0,50mg/L plant height,leaf length,stem length,antioxidant enzyme activities value and these indicators of Bermuda grass is higher than non-waterflogging with low MDA content,which indicated waterflogging in the case of low concentrations of Cd can reduce the harm of Bermuda grass to a certain extent.(4)With the increase of Cd concentration under non-waterflogging and waterflogging conditions,Bermuda grass underground and aboveground Cd accumulation showed a linear upward trend,and the values of flooded value is higher than non-flooded,the WL+150Cd treatment of Bermuda grass and shoot Cd accumulation reached the maximum value respectively 1461.60 and 3728.08 mg/kg,which indicated that waterflogging could promote the absorption of Cd by Bermuda grass;Under 50 Cd treatment,root accumulation coefficient reached a maximum value of 129.5,stem leaf accumulation coefficient reached a maximum value of 115.3,50Cd+WL treatment transfer coefficient reached a maximum value of 3.75,which indicated Bermuda grass' s ability of accumulation and transportation for Cd is very good;The accumulation ability of cadmium in each part of Bermuda grass is leaf > root > stem.In summary,when the tolerance threshold of Bermuda grass on cadmium reached 150 mg/L,it could have normal growth in a certain range of cadmium content,and ability of accumulation and transportation is very strong,which can be used as excellent species and vegetation suffered flooding and heavy metal pollution in recovery area.