中文摘要：

植物机械强度是一个十分重要的农艺性状，为了解作物控制机械强度的机制，本文对一个水稻脆性突变体[bc7（t）]叶进行了细胞学观察及叶细胞化学组成分析。光镜和电镜观察都发现突变体厚壁细胞的细胞壁变薄；对细胞壁成分的化学分析显示突变体纤维素含量明显低于对照，硅含量明显升高，而木质素变化不明显；木质素的组化反应也显示了木质素在突变体和对照之间差异不大；X-射线微区分析表明，硅元素在突变体叶表面明显提高。上述结果表明，突变体叶纤维素含量的降低影响了厚壁细胞次生壁的形成，导致细胞壁变薄，机械强度降低，硅含量的升高有助于突变体增强机械强度。

英文摘要：

Plant mechanical strength is an important agronomic trait. A rice brittle mutant bc7（t） which derived from japonica variety Zhonghua 11 by radiation of ^60Co-γ displayed normal phenotype similar to its wild type （WT） plants except for the fragility of all plant body. To understand the mechanism of controlling plant mechanical strength, the anatomical structure and chemical features of leaf of brittle mutant bc7（t） were investigated. Anatomical analyses were carried out by means of various microscopic techniques, such as light microscopy, scanning electron microscopy and transmission electron microscopy. It was found that the cell walls of sclerenchyma cells of leaf sheath and leaf blade in the mutant were thinner than that in WT. For histochemical localization of lignin, fresh freezing-cut transverse sections of leaf blade and sheath were stained with Wiesner reagents. Responding to the Wiesner reaction, the sclerenchyma cells below the epidermis, vascular bundle sheath and xylem were stained red. Though no noticeable staining difference in leaf blade between WT and mutant, the sclerenchyma cells of leaf sheath of mutant were stained slightly deeper than that of WT. Separation and purification of cell wall of leaf blade and sheath were carried out. The lignin content of cell wall was determined by thioglycollic acid method, the results revealed a slightly higher lignin content in mutant than in WT without significant difference. The cellulose content of cell wall was assayed with the anthrone reagent; the results showed that the amount of cellulose of leaf blade and sheath in mutant was significantly lower than that in WT, The test of silicon content of cell wall showed an increased content in the mutant. The energy dispersive X-ray micro-analysis attached to the FE-SEM provided the information on the distribution and content of silicon in the epidermal cells of leaf blade and sheath. The X-ray map analysis at the upper and lower epidermis of leaf blade and outer epidermis of leaf sheath showed that