中文摘要：

【目的】橡胶树乳管细胞所富含的一种特征性细胞器是橡胶粒子,其主要功能是合成和贮存天然橡胶,但该细胞器的起源仍无定论。通过观察不同发育阶段乳管细胞的超微结构,比较分析橡胶粒子的发育与其他细胞器之间的关系,探明橡胶粒子的起源,为进一步认识橡胶粒子的功能奠定基础。【方法】利用透射电子显微镜技术,观察橡胶树萌条幼茎和成龄树树干的树皮中不同发育阶段的乳管细胞超微结构,分析最初的橡胶粒子与其他细胞器之间的关系。【结果】幼嫩萌条的初生乳管细胞的细胞质浓厚,可辨认的最初的橡胶粒子呈电子致密小球,主要分布在富含内质网和核糖体的区域。成龄树树干树皮形成层附近的幼嫩次生乳管细胞中,分布有大量的内质网和比较稀疏的橡胶粒子,其他细胞器的形态也较清晰,适合作为研究橡胶粒子起源的材料。在高倍放大的情况下,可观察到直径约50 nm、内部呈电子致密的球形小颗粒直接与内质网相连接,在内质网周围存在直径逐渐增大的有明显界膜的球形颗粒,并且这些颗粒的内部开始呈现电子透明,这些特征与橡胶粒子的发育相吻合。虽然高尔基体周缘也存在一些球形泡状结构,但这些小泡的内含物呈颗粒状,与最初形成的橡胶粒子明显不同。在充分发育的成熟乳管细胞中充满橡胶粒子,而树皮外侧的衰老乳管细胞开始出现橡胶粒子凝固,在这2种类型的乳管细胞中都很难分辨不同类型的细胞器,因此不适合作为研究橡胶粒子起源的材料。【结论】通过观察不同类型和不同发育阶段的乳管细胞超微结构可知,靠近形成层的幼嫩次生乳管细胞是研究橡胶粒子起源的最佳材料。在这一发育时期的乳管细胞中,可以清晰地观察到最幼嫩的橡胶粒子与内质网紧密相连,而与其他细胞器没有直接联系,因此本文结果支持橡胶粒子主要起?

英文摘要：

【Objective 】 The laticifer cells in rubber tree（ Hevea brasliensis） are characterized by the presence of abundant rubber particles,a kind of organelles specific for rubber biosynthesis and storage. However,the origination of rubber particles still remains controversial. Ultrastructural observation was performed to ascertain rubber particle origination and lay a foundation for further understanding of the function of rubber particles. 【Method 】By using transmission electron microscope（ TEM） technique,the ultrastructure of laticifer cells at different development stages in the bark of both tender shoot and mature rubber tree trunk was investigated.【Result】In primary laticifers of the tender shoot,the recognizable original rubber particles appeared as small electron-dense spherical particles in the dense cytoplasm. The particles mainly distributed in the regions where abundant endoplasmic reticula（ ER） and ribosomes were present. In the trunk of mature rubber tree,the young secondary laticifer cells near the vascular cambia contained abundant endoplasmic reticula and scattered rubber particles as well as various organelles with legible outlines,which is suitable for exploring the origination of rubber particles. At higher magnification,small electron-dense spherical particleswith a diameter of about 50 nm were found to connect to the ERs while larger spherical particles with clear membrane and electron-lucency dispersed in the surrounding. The changes in diameter and interior of the spherical particles were consistent with the rubber particle development. There were small spherical particles near Golgi body. These particles were different from the original rubber particles in that their inclusion appeared to be granular other than homogenous electron-dense. The matured and ageing secondary laticifer cells were not suitable for investigating organelle origination since the matured secondary laticifer cells filled with rubber particles while rubber particle coagulation occurred in the ageing se