| Biomineralization, a universal phenomenon, is to form inorganic mineral structure by biological process. Such structures as animal's macro vertebra of apatite and higher plant's nanoparticles of silica play essential roles in living things. The evidence is overwhelming that silicon promotes the growth of plants and often confers on plant tolerance of abiotic and biotic stresses. Because great deals of researchers are focusing on the biophysical functions of silicon, it is not enough to reveal the intrinsic action of silicon biomineralizaion in higher plants. Based on the principal of silica deposition in mammals, the mechanism of silica mineralization in diatoms and sponges and the microenvironment of silica in higher plants, a hypothesis was made, which postulated that the biomineralization of silicon in higher plants was induced by lignin synthesis or/and special protein. The results are as follows:1. The structure unit of rice phytolith is rods and particles of nanometers, which made the rice special characters. Phytoliths from different kinds of rice were investigated under electron microscope and maps of dimensional graphs of silica bodies were obtained in detail. All of them are empty at the center, with a wall of silica of rod or particle of nanometers. The rods are of different lengths, which are from 35 to 55 nm in width. The particles are at the average diameter of 15nm. In the fan-shaped silicas, only particles are present which are 2nm in size. Particles trend to join together to from bigger ones. According to nanometer theory, rice phytoliths must have properties of nanometer materials: surface effect, small size effect, quantum effect and macro quantum tunnel effect. The micro infrared scanning experiment showed that phytolith absorbs light at 9 m, which is between the value of 8-12 urn from Idso's measurement of nanometer SiO2: the radiation coefficient is between 0.80 and 0.90. By radiation theory, the higher the radiation coefficient, the cooler the surface. Therefore, it is reasonable that silicon in higher plants could reduce the temperature when the plant is under higher thermal stress. Besides, rice phytolith has a strong absorb peak at UV-C of 190nm and the phytolith from lemma has a higher absorbance at UV-B of 280. Such absorbance could reduce the damage from UV.2. Silica nanospheres were induced by peroxidase-catalyzed phenol polymerization. A simulated experiment was carried out at room temperature and pressure. Silica nanosphere deposition appeared when peroxidase, phenol and H2O2 was mixed into silica solution. These spheres were exactly the same as silica nanosphers induced by sallifins isolated from diatom by Kroger, with the diameters of 40-450nm, spheres joining together to form a net structure. The size and net structure depend on the kind and concentration of phenol, the donated silicon and its concentration. The amount of silica deposition was decided by the concentration of silicon and phenol, with silicon saturate effect and phenol saturate effect. It had the most deposition when phenol and silicon were at the same molar concentration.3. Rice lignin induced silica deposition to lignin-silica nanospheres. Extracted from rice stems and leaves, lignin was treated with 2%HF buffer to remove the combined silica. At room temperature and pressure, when 25mg of lignin was put into 1% borax solution (pH10.5), precipitation occurred. This precipitation induced silica deposition, forming lignin-silicananospheres, with the diameter increased from 35nm to 90nm. Energy-dispersive X-ray spectra showed that a lot of silicon presented in the precipitation. Compared with that, lignin in DMSO was degraded and failed to precipitate, and it couldn't induce silica nanospheres. This result showed that it is polyphenols as lignin not mono phenols that induce silica precipitation.4.Organic compound that induced silicon mineralization in rice was on the surface of the phytolith. Phytoliths were extracted by concentrated acid or self-deposition separately.
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