Alleviative Effect And Mechanism Of Exogenous Silicon-alleviated Cd Stress On Pennisetum Rich

Cadmium is one of the main major heavy metals of soil pollution,with characteristics of strong biological toxicity and large migration.Accumulation of cadmium in organisms can affect plant material accumulation and energy metabolism,which will affect the normal growth of plants.Pennisetum Rich is annual or perennial grasses,with excellent characteristics of large biomass,strong tolerance and high nutritional content.It is the important forage grass in tropical,subtropical,and temperate regions.Also,it is a quality source of energy grass and ornamental grass.Pennisetum Rich is suitable for planting in the south of our country.In this experiment,Pennisetum americanum and P.americanum×P.purpureum are as materials,adopt the method of potting in soil,study the damage mechanism of cadmium toxicity on Pennisetum,and discuss alleviation effect and its mechanism of silicon to two kinds of Pennisetum under Cadmium Stress.The experiment results are as follows:(1)With the increase of Cd2+ concentration,the plant height,fresh weight and dry weight of the two kinds of Pennisetumdecreased gradually,the leaf width did not change significantly.With the increase of Cd2+ concentration,Two kinds of Pennisetum's Leaf cell membrane permeability,MDA content,soluble sugar content and proline content showed an increasing trend.Under high Cd(Cd40?Cd80)concentration treatment,cell membrane permeability,MDA content,soluble sugar content and proline content showed a significant increasing trend.The low Cd(Cd10?Cd20)concentration treatment had Promoting effect to activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)of two kinds of Pennisetum.The high Cd(Cd40?Cd80)concentration treatment had inhibitory action to activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)of two kinds of Pennisetum.Under Cd treatment,net photosynthetic rate(Pn),transpiration rate(Tr)and stomatal conductance(Gs)of two kinds of Pennisetum decreased significantly,but intercellular carbon dioxide concentration(Ci)of two kinds of Pennisetum elevated.And,Under high Cd(Cd40?Cd80)concentration treatment,chlorophyll content of two kinds of Pennisetum decreased significantly.(2)Silicon is clearly relieved the inhibition of cadmium on growth of two kinds of Pennisetum,and improved the two kinds of Pennisetum's plant height,fresh weight and dry weight,when they under the Cd treatment.When the concentration of silicon is 4.0mmol·L-1,the most significant effect of silicon on two kinds of Pennisetum ease.Different concentrations of silicon(1.0?2.0?4.0mmol·L-1)can reduce the MDA content of two kinds of Pennietum,maintain proline content and soluble sugar content to a certain level,increase the activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT),reduce the degree of membrane lipid peroxidation.When the concentration of silicon is 2.0mmol·L-1,it can significantly improve the activities of peroxidase(POD)and catalase(CAT)of two kinds of Pennisetum,which under Cd40 treatment.When the concentration of silicon is 4.0mmol·L-1,it can significantly improve the activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)of two kinds of Pennisetum,which under Cd80 treatment.In addition,silicon treatment can increase chlorophyll content and photosynthetic capacity,when these two kinds of Pennisetum suffered from the toxicity of Cadmium.With the increase of silicon concentration,net photosynthetic rate(Pn),transpiration rate(Tr)and stomatal conductance(Gs)of two kinds of Pennisetum increased,and intercellular carbon dioxide concentration(Ci)of two kinds of Pennisetum decreased.When the concentration of silicon is 4.0mmol·L-1,Chlorophyll content of two kinds of Pennisetum,which under high Cadmium treatment(Cd40?Cd80),increased significantly.(3)With the increase of Cd2+ concentration,the Cadmium content of the aboveground part and roots of two kinds of Pennisetum increased gradually,and the Cadmium content of roots greater than the Cadmium content of the aboveground part.After adding silicon treatment,the Cadmium content of the aboveground part and roots of two kinds of Pennisetum decreased.With the increase of silicon concentration,the Cadmium content of the aboveground part decreased gradually.