Effects Of Nitrogen Fertilizer Forms On Cd Absorption,Translocation And Accumulation

With the development of economic globalization,the problem of heavy metal pollution has attracted global attention.Cadmium(Cd)pollution is an important source of pollution in agricultural products.Cd is particularly easy to be absorbed by roots in crops to migrate and accumulate in crop seeds.The food chain is used as a carrier.Into the human body.Wheat is one of the most important food crops and occupies an important position in the food security of countries all over the world.There are differences in the effects of nitrogen fertilizer forms on cadmium absorption,transportation and accumulation in wheat.In this paper,potted and hydroponic experiments,using Bainong 207 variety as the object,explored the effects of nitrogen fertilizer forms on wheat cadmium absorption,transportation and accumulation.Under cadmium stress conditions,The feasibility of nitrogen fertilizer forms to reduce the content of cadmium and restrict its transport to grains was discussed.The differences in cadmium absorption,transport and cadmium detoxification mechanisms among nitrogen fertilizer forms were analyzed.:(1)In the hydroponic system,compared with the control group,with the increase of cadmium concentration,the biomass of each treatment,photosynthetic parameters,relative chlorophyll content SPAD,root growth,nitrogen accumulation inhibition degree increased,cadmium content and accumulation amount,unit mass Root absorption increases the degree of oxidative damage,and the extent of protein damage increases,thereby inhibiting the growth of wheat seedlings.Under the conditions of Cd0,Cd15 and Cd30,the optimum ratio of nitrate to ammonium is 2:1,1:1 and 1:2,which shows that with the increase of cadmium stress concentration,the optimum ratio of ammonium nitrate shows a decreasing trend.Combined application of ammonium nitrate can significantly affect the cadmium content,cadmium accumulation,and cadmium absorption per unit mass of roots in wheat seedlings,mainly because the increase in ammonium nitrogen can significantly reduce the root cadmium absorption capacity,and nitrate nitrogen can enhance root cadmium absorption Ability,and the kinetic test in the concentration and time of Cd further proves this conclusion.Combined application of ammonium nitrate can increase the content of soluble protein and ASA in the shoots and roots of wheat seedlings.T3 treatment under Cd15 conditions and T4 treatment under Cd30 conditions can promote the distribution of Cd into the cell sap,reduce the distribution of Cd in organelles,and promote Cd transforms from the active state to the inert state,thereby alleviating the Cd toxicity of wheat seedlings.(2)In the pot system,the absorption of cadmium by wheat basically ends at the flowering stage.The emergence and jointing stage is the main and rapid stage of cadmium absorption.The cadmium in the grain comes from the root system(29%)and the stem(71%)storing cadmium.Re-transfer,the form of nitrogen fertilizer did not significantly affect the re-transfer of cadmium stored in vegetative organs.The difference in cadmium content in grains caused by nitrogen fertilizer forms is caused by the accumulation of cadmium in stalks and roots before flowering and the difference in grain yield.Nitrate-nitrogen treatment has the highest grain yield and the lowest cadmium content.It is recommended to apply nitrate-nitrogen fertilizer in cadmium-stressed soil.Nitrate nitrogen fertilizer treatment promoted wheat root elongation and increased the relative content of flag leaf chlorophyll,which increased the thousand-grain weight and yield;ammonium nitrogen fertilizer treatment reduced root p H,resulting in plant cadmium accumulation and grain cadmium content significantly higher than other nitrogen fertilizer treatments.Nitrate nitrogen with DCD treatment reduces the cadmium content of the whole plant and promotes the increase of nitrogen,phosphorus and potassium content of the whole plant,thereby promoting dry matter accumulation of wheat;ammonium nitrogen treatment significantly inhibits the dry matter accumulation of wheat and increases the cadmium of the whole plant at maturity.content.Compared with the treatment without adding DCD,the addition of DCD promoted the increase of nitrogen,phosphorus and potassium content of the whole plant in each treatment.Nitrate nitrogen,nitrate nitrogen with DCD,nitrate ammonium ratio and nitrate ammonium ratio with DCD treatments significantly reduced the damage of wheat flag leaves.