Research On The Physiological Functions And Deposition Mechanisms Of Silicon In Rice

There are two parts in this paper. One is the physiological functions of silicon in rice under UV-B and high temperature, and the other is the mechanisms of silicon deposition in rice leaf. The main results are as following:On the research of the effect of silicon on ultraviolet-B(UV-B) resistance of rice leaves, the methods include nutrient solution culture, chemical components analysis and microscope technology. It is concluded that the elevated UV resistance of silicon-treated leaves is due to the increase of the UV-B compounds in epidermis induced by silicon. The insoluble UV-absorbing compounds and the soluble phenolic compounds together constitute a barrier against UV-B.The nutrient solution culture and microscope technology are adopted in the effects of Silicon on anther dehiscence and pollen shedding in rice under high temperature stress. Experimental data shows that the percentage of anther dehiscence and the amount of pollen shedding increased by 130% and by 66%, respectively, in Si-treated rice plants. In addition, the diameter of pollen grains is larger in Si-treatment and the changing tendency keeps steady a longer time than the control under high temperature stress.Isolation of native silica bodies from rice leaves by low temperature homogenizing and sieving method firstly is developed in the mechanism of silica deposition in rice leaves. This method is better than the traditional dry ashing or wet digestion methods, because the organic matter in the silica bodies will not be destroyed by our new method. Analysis of organic biological molecules associated with the silica is important for revealing the mechanism of silica precipitation in rice leaves. In the molecular mechanism of silica deposition in rice leaves, we exert the electrophoresis, micro sequencing analysis of protein, synthetic peptide method and bioinformatic technology into this research. A group of different proteins are purified from silica bodies, among which there are four proteins with the ability to precipitate silica acid. The N-terminal amino acid sequence of the protein (125KDa) is analyzed with micro sequencing analysis of protein. It is obvious that this protein is completely homologous with a protein registered AAO72557.1 in NCBI database. The biochemical property of this protein is similar with those inducing silicon to precipitate in diatom and cucumber, but its primary structure is different from them. It means that the protein (125KDa) is a new kind of protein involved in the silica deposition metabolism. The synthetic high conserved and repeated sequence from protein (125KDa) can induce orthosilic acid to polymerize into silica precipitate immediately.