| Cadmium(Cd)is a non-essential trace element of plants and is highly toxic to plants.It is easily absorbed by rice roots,causing excessive levels of cadmium in rice and being absorbed by the body through the food chain,affecting human health.Selenium(Se)is a kind of trace element in nature.It is one of the essential nutrients in the living organism.It is found that there is an antagonistic effect between selenium and cadmium.The addition of selenium can alleviate the damage of rice under cadmium stress.In this study,four different forms of selenium(Nano-Se,Se(?),Se(?),SeMet),three selenium levels(0?M,1?M,2?M)and two cadmium levels(0?M,20?M)were used.To investigate the effects of different forms of selenium on rice growth,photosynthetic characteristics,root growth,antioxidant system response,cadmium in plant morphology and subcellular distribution,and to explore the cell physiology and biochemical mechanism of selenium alleviatingcadmium toxicity in rice.The following are the main results:1.Trentment 20?M cadmium significantly reduced plant height,shoot dry weight,chlorophyll content,root activity,net photosynthetic rate,root surface area and root volume of rice seedlings.The application of 1?M of Nano-Se,Se(?),SeMet and 2?M Nano-Se significantly attenuated the symptoms of rice seedling toxicity caused by 20?M cadmium.Among them,the application of 1?M SeMet was the best,while the 2?M SeMet deepened the cadmium stress in rice.It indicated that selenium had a dose effect on rice,low concentration of selenium promoted rice growth,and high concentration of selenium inhibited rice growth.2.The application of 2?MSeMet significantly increased the iron plaque of the root surface of rice seedlings under cadmium stress,and the distribution ratio of cadmium in the iron plaque of root surface increased significantly,indicating that selenium can promote the formation of iron plaque in roots of rice roots.Appling 1?M Nano-Se,SeMet and 2?M Se(?),Se(?)significantly reduced the cadmium content in the roots of rice seedlings treated with 20?M cadmium.The cadmium content in the shoots of rice seedlings under the four different forms of selenium treatment was significant.Falling.The application of selenium can significantly reduce the absorption rate of cadmium in rice roots and the transfer of cadmium from root to shoot.The application of 1?MSeMet is the best in reducing the absorption of cadmium by rice roots and the transfer of cadmium from root to shoot.3.The appliaction of selenium significantly reduced the proportion of cadmium in the cell wall and significantly increased the proportion of cadmium in the soluble fraction.Selenium significantly increased the proportion of cadmium extracted from sodium chloride in rice seedlings and decreased the proportion of cadmium extracted from deionized water.It can be concluded that selenium reduces cadmium toxicity and migration in plants by reducing the mobility of cadmium or by partitioning cadmium.The effect of treatment with 1?M SeMet is the best.4.20?M cadmium significantly increased the MDA content in the shoot of rice seedlings,significantly increased the SOD and POD activities in the shoot of rice seedlings,significantly reduced the activity of CAT and GSH-PX.The application of 1 ?M four different forms of selenium significantly reduced the activity of SOD and POD in the shoots of rice seedlings under cadmium stress.The results showed that selenium could alleviate the damage caused by cadmium stress by regulating the response of antioxidant enzyme system in rice,and the effect of applying 1 ?M SeMet was the best.5.The application of 1?MSeMet at three concentrations of four different forms of selenium is the best in alleviating cadmium stress in rice,reducing cadmium uptake by rice and inhibiting the transfer of cadmium from roots to shoots... |
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