Nanoscale Silicas in Oryza Sativa L. and Their UV Absorption
FANG Jiang-yu1,2,WAN Xiao-chun1*,MA Xue-long2
1. Postdoctoral Research Station in Horticulture, Anhui Agricultural University, Hefei 230036, China 2. Biodiversity Institute, Huangshan University, Huangshan 245021, China
Abstract：To reveal the unique microstructure of silica in rice and its absorption of ultra violet, wet digestion was chosen to isolate silica bodies from rice leaves and bract according to the fact that concentrated acid cannot destroy glass made of SiO2. A mixed solution of sulfuric and nitric acids was applied to the leaves and bract of rice, respectively. After keeping the treated samples in 60-70 ℃ water bath for 30 hours and times of washing and sedimentation in water, pure silica bodies were obtained. The detection by X-ray photoelectron spectroscopy(XPS) indicated that there was 35.05% of carbon 10 nm under the surface of the silica body, much more than the amount of 5.88% on the out surface which might be due to the contamination of the air contact with the sample. This fact showed that acid couldn’t get into the silica body to oxidize the inner organic compounds to alter the structure, therefore the chemical and physical properties of the silica measured could account for the original status in the leaf and bract. Scanning electron microscopy and transmission electron microscopy observation revealed that the silica body of rice is made up of inseparable SiO2 particles of 1-2 nm, sticking slackly to form nano-scale rods of average 45 nm wide and arranging in the same direction. Besides, there were lots of pores inside the inner part of the silica body, including both micron-scale pores(≤1 μm) and nano interstitial pores(≤1-2 nm). The bract silica has the greatest absorption at 285 nm of UV-B, while the leaf silica has a very low UV absorption, indicating that silica in the two organs of rice has different mechanism of radiation resistance.
[1] Allen D J, Nogues S, Baker N. Journal of Experimental Botany, 1998, 49(328): 1775. [2] Ishibashi T, Kimura S, Yananoto T, et al. Gene, 2003, 308: 79. [3] WANG Zhong(王 忠主编). Plant Physiology(植物生理学). Beijing: Agricultural Press of China(北京: 中国农业出版社)，2000. 350. [4] Nayak L, Biswal B, Ramaswamy N K. Journal of Photochemistry and Photobiology B: Biology, 2003, 70: 59. [5] International Rice Research Institute. Program Report for 1990. Los Banos, Laguna, Philipines，1991. [6] Mizutani Y, Nago S. Journal of Applied Polymer Science, 1999, 72: 1489. [7] Epstein E Silicom. Annual Review of Plant Physiology and Molecular Biology, 1999, 50: 641. [8] HU Ding-jin, WANG Fu-hua(胡定金, 王富华). Hubei Agricultural Science(湖北农业科学), 1995, 5: 33. [9] LIN Guan-fa, ZHENG Mao-sheng, BAI Zhen-quan, et al(林冠发, 郑茂盛, 白真权, 等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2005, 25(1): 1187. [10] XU Yi, TANG Shou-yuan, ZHANG Xiao-feng(徐 溢, 唐守渊, 张晓风). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2004, 24(4): 475. [11] ZHANG Lei(张 蕾). Spectroscopy and Spectral Analysis(光谱学与光谱分析),2004, 24(11): 1432. [12] Harrison C C. Phytochemistry, 1996, 41: 37. [13] HUANG De-huan(黄德欢). Nanometer Technology and Application(纳米技术与应用). Shanghai: Chinese Spinning and Weaving University Publishing House(上海: 中国纺织大学出版社)，2001. 130. [14] Ma J, Nushimura K, Takahashi E. Soil Science and Plant Nutrition, 1989, 35(3): 347. [15] ZHANG Wen-xu(张文绪). Acta Agronomica Sinica(作物学报), 1999, 25(5): 591. [16] Li W, Shi X, Wang H, et al. Acta Botanica Sinica, 2004, 46(6): 691.
