Salicylic Acid Affects Physiological,biochemical And Molecular Mechanisms Of Rice Cadmium Absorption

As the main food crop,rice is closely related to human survival.And the increasing cadmium pollution seriously endangers the food security.In this experiment,high cadmium accumulation FP36 and low cadmium accumulation EJN1 were selected for rice,and salicylic acid（SA）in plants as signal molecules had positive effects in various adverse environments.The defense mechanism of rice under cadmium stress by exogenous SA addition was studied by means of mutual verification between hydroponics and soil culture,and its principle was explained and elaborated from the perspective of physiological,biochemical and molecular mechanisms.Different concentrations of SA and the different ways of applying for rice to withstand adversity has promoting effect under cadmium stress,in hydroponic experiment section,100μmol·L^-1exogenous SA to the promoting effect of the physiological indexes is best,including EJN1 Cd content in root system in the 100μmol·L^-1and 300μmol·L^-1treatment decreased by 20%and 43%respectively,Cd content in the leaves decreased by 38%and39%respectively.The Cd content in the roots of FP36 decreased by 11%and 17%,respectively,under the treatment of 100μmol·L^-1and 300μmol·L^-1,and the Cd content in the leaves of FP36 decreased by 7%and 19%.All the other physiological and biochemical indexes reached the best state when SA was 100μmol·L^-1.The hydroponics experiment and soil culture experiment with 100μmol·L^-1SA were performed.The experimental results show that Cd,Fe,Mn element content in rice roots than in leaves,and the above elements content in the whole growth period of rice harvest is below the ground,and after treated with SA,each place cadmium accumulation amount decreased obviously,and increased iron accumulation and further from the side also confirm under cadmium stress of iron cadmium competition mechanism.Exogenous SA had a certain alleviating effect on the growth inhibition of plants under cadmium stress,and the changes of physiological indexes such as chlorophyll,SOD,POD,CAT and soluble protein were the most obvious when exogenous SA was 100μmol·L^-1,and the decomposition efficiency of H₂O₂in plants under cadmium stress was the highest.The results indicated that SA could regulate the internal environment of the plant and cooperate with all parts to resist cadmium stress damage.Cadmium in the growing environment was absorbed into the rice plant through the root system,and the Fe transporter in the HMA family on the cell membrane and OsNRAMP1 in the NRAMP family entered into the cell.In this process,Cd and Fe formed a competition mechanism,indicating that Cd in the free state in the iron-deficient environment would occupy the Fe transport channel.OsIRT1,OsNRAMP1,OsYSL15 and OsNAS3 were all strongly induced by iron deficiency,and their expression levels showed a downward trend during the whole growth period due to the increase of Fe content in plants.