猫屎瓜乳汁道形成过程中显微和超微结构变化以及与橡胶产生的关系

橡胶植物猫屎瓜的含胶结构是一种溶生的乳汁道。它是在果实发育过程中,由部分外表皮细胞经过凹陷、封闭转变为分泌表皮细胞,再由它们经过破毁、解体形成的溶生胞间道系统。通过组织化学和细胞学研究,在开花后10天内,幼果外表皮为同形组织,细胞内无橡胶颗粒;当凹沟出现后,外表皮开始分化为两类组织:外表皮和分泌表皮,只在后者细胞内产生橡胶颗粒,直至乳汁道形成。透射电镜观察表明,分泌表皮细胞内无黄色体和F-W复合体,其橡胶颗粒的产生与内质网槽库和电子致密小颗粒(多聚体)有关,而液泡中的纤丝结构又与团块状橡胶物质的形成有关。为此,猫屎瓜的含胶结构和橡胶产生方式既不同于巴西橡胶树等的乳汁管,又与杜仲等的含胶细胞不完全相同,有其特殊性。猫屎瓜的橡胶在分布上和形成时间上的局限性是和乳汁道的特殊形成方式密切相关的。此种特点,为研究橡胶的生物合成机理提供较好材料,并为今后提高该植物的橡胶产量提供了参考资料。

Studies on Relations between Rubber Synthesis and Microstructure and Ultrastructure of Laticiferous Canals of Decaisnea fargesii in Fruit Development

Rubber-bearing structure of Decaisnea fargesii, a lysigenous intercellular canal system, is developed by the disintegration of secretory epidermal cells which is differentiated from the part of epidermal cells of fruit by the depression and concealment. Histochemical and cytological studies indicate that the formation of rubber is limited in the protoplasm of the secretory epidermis of pericarp. Generally, about ten days after blooming and fertilization, the rubber granules begin to appear in the epidermal cells which are located in the depressions of the young pericarps. And then, following the formation and development of the secretory epidermis, the rubber granules increase progressively and stop in 60 days old. During the development of fruits, the epidermal cells of the carpel wall are divided into the pericarpial epidermis and the secretory epidermis. The latter forms rubber granules successively. Finally, when these cells are full of the granules, they lose their vital function and lyse into laticiferous canals. Electron microscope observations suggest that the cisternae of ER and some electron dense granules are involved in the formation of rubber granules, and mass-like rubber materials are formed in fibril structure which appears in the vacuoles of the secretory epidermal cells in late developmental stages of fruits. Lutoid and F-W complex scarcely occur in the secretory epidermal cells of laticiferous canals of Decaisnea fargesii. Therefore, the both rubber-bearing structure and the formation of rubber granules in Decaisnea fargesii are prominently different from those in Hevea brasiliensis and Eucommia ulmoides.