中文摘要：

稳定性硅同位素在植物体内的组成模式对研究硅生物循环、植物硅积累的机理具有重大意义。通过水培试验，研究了成熟期水稻叶内硅同位素组成及Si、K、Na、Ca和Mg营养元素的分布情况。试验结果表明，将水稻叶沿长轴按叶鞘、叶片基段、叶片中段和叶片顶段4部分划分后，各段的Si质量分数和δ^30Si值都存在显著差异，并呈现从叶下部到上部逐渐增加的一致趋势。在测定的其它营养元素中，只有Ca在水稻叶中的分布与Si类似，K和Na在叶鞘中的质量分数高于叶片，Mg在叶不同部位质量分数没有显著差异。本试验中水稻叶不同部位δ^30Si值变化范围是-0．25％-0．23％，超出了目前已知陆生植物样品δ^30Si值的变化范围（-0．17％～0．25％）。试验结果显示了水稻叶内硅分布主要受蒸腾作用的影响，硅同位素在叶中的分馏属于同位素动力学分馏。

英文摘要：

An understanding of the variations of silicon （Si） isotopes in plant tissues has potentially important applications in elucidating the biogeochemical Si cycle and Si accumulation in plants. Si isotope compositions and Si, K, Na, Ca, Mg distribution among different parts of rice leaf at maturity were studied by hydroponic culture. For δ^30Si values and Si distribution in different parts of rice leaf, there was a consistent increasing trend from lower to upper tissues （leaf sheath 〈 leaf blade base 〈 leaf blade middle 〈 leaf blade top）. Compared with the distribu- tion patterns of K, Na, Ca and Mg in rice leaf, Ca showed a similar pattern with Si. The concentration of K or Na in leaf sheath was higher than that in leaf blade. There was no significant difference in the Mg concentration for each leaf part. It had been reported that the measured δ^30Si values of phytholiths for surficial material on earth varied from -0. 17% to 0. 25%. In present experiment, however, the magnitude of δ^30Si variation among different parts of rice leaf was even greater, ranging from -0. 25% to 0. 23%. It is suggested that evapotranspiration was the driving force for an upward flow of a silicon - bearing solution and silica translocation in rice leaf. Si isotope fractionation in rice leaf could be recognized as a kinetic isotope fractionation process.