Effects Of Silicon Preparation On Physiological Characteristics And Cadmium Accumulation Of Rice Seedlings In Under Cadmium Stress

Silicon（Si）is one of the indispensable elements in the growth and development of rice.Rice is a crop which is easy to enrich cadmium.Cadmium ions in soil are easily absorbed and transported upwards by rice roots,and finally a large amount of cadmium is enriched in rice grains,which affects the safe production of rice.Two rice varieties,Songjing 16 and Dongnong 427,were selected in this experiment.Three cadmium concentration gradients were set through hydroponic experiment.Seven days after cadmium stress,three different types of silicon preparations,Si-50G,Si-60G and Si-TG,were sprayed.The effects of different silicon preparations on photosynthetic pigment content,malondialdehyde（MDA）content,superoxide dismutase（SOD）activity,peroxidase（POD）activity,catalase（CAT）activity and cadmium accumulation in different parts of rice seedlings under heavy metal cadmium stress were compared and analyzed.It provides a scientific basis for the application of silicon preparation to improve the cadmium resistance of rice,and has important theoretical and practical significance for ensuring the safe production of rice and the subsequent research and development of silicon fertilizer.The results showed that silicon preparation could regulate the physiological characteristics of rice seedlings under cadmium stress to a certain extent,but the effects of silicon preparation were different according to different rice varieties and different cadmium stress degrees.（1）Silicon preparation can increase photosynthetic pigment content of rice leaves at seedling stage under cadmium stress.All the three silicon preparations can significantly increase the photosynthetic pigment content of rice leaves under Cd stress at seedling stage.The photosynthetic pigment content of Songjing 16 leaves treated with Si-50G,Si-60G and Si-TG had the best effect when cadmium concentration was 200μg·L^-1,which increased by 50.16%,37.60%and 39.16%respectively compared with CK.The photosynthetic pigment content of Dongnong 427 leaves treated with Si-50G,Si-60G and Si-TG had the best effect when cadmium concentration was50μg·L^-1,which increased by 57.56%,45.92%and 55.57%respectively compared with CK.（2）The content of MDA in rice leaves increased with the increase of Cd concentration,and the content of MDA in rice leaves decreased in different degrees after treated with silicon.Under different Cd concentrations,the optimal treatment for both rice varieties was si-50g.For Songjing16,MDA content in leaves decreased by 24.12%,28.30%and 28.41%,respectively;For Dongnong427,MDA content in leaves decreased by 20.33%,37.04%and 26.36%respectively.（3）Silicon preparation can improve the activity of antioxidant enzyme system in rice leaves at seedling stage under cadmium stress.The activities of SOD and POD in leaves of Songjing 16 and Dongnong 427 after cadmium stress were all improved by three kinds of silicon preparations,among which the SOD content and POD content of Songjing 16 sprayed with Si-50G increased significantly by 41.65%,44.22%and 43.45%,respectively.Si-60G increased SOD content of Dongnong 427 leaves by 26.17%,46.99%and 31.22%respectively.POD content increased by80.23%,60.16%and 128.73%.CAT activity in leaves of Songjing 16 treated with Si-50G increased by 153.24%when cadmium concentration was 50μg·L^-1,and CAT activity in leaves of Dongnong 427 treated with Si-60G increased by 198.40%when cadmium concentration was200μg·L^-1.（4）Silicon preparation can reduce cadmium accumulation of rice plants at seedling stage under cadmium stress.Si-50G,Si-60G and Si-TG can reduce the cadmium content of rice plants and inhibit the cadmium absorption capacity of rice roots.When the cadmium concentration was200μg·L^-1,the cadmium accumulation content of Songjing 16 roots treated with Si-60G decreased by 51.59%.When the cadmium concentration was 50μg·L^-1and 500μg·L^-1,the cadmium accumulation content of Dongnong 427 roots treated with Si-TG decreased by 50.17%and 50.43%.Cd accumulation in the stems and leaves of Songjing 16 treated with Si-50G decreased by 46.96%,63.81%and 40.35%,respectively.The accumulated content of cadmium in the stem and leaf of Dongnong 427 treated with Si-TG was significantly reduced by 50.15%and 49.03%when the cadmium concentration was 50μg·L^-1and 200μg·L^-1,respectively.In conclusion,Si-50G treatment has the best comprehensive effect on various indicators measured by Songjing 16,Si-60G treatment has the best comprehensive effect on various physiological indicators of Dongnong 427,and Si-TG treatment has the most significant effect on reducing the accumulation of cadmium in Dongnong 427.