甜菊愈伤组织生长、分化与甜菊糖苷积累的关系

耐菊（Steviarebaudiana）愈伤组织中甜菊糖苷的积累与愈伤组织的生长呈负相关、与愈伤组织细胞的组织化及转绿呈正相关。愈伤组织芽的分化并不是积累较高水平甜菊糖苷的必要前提。绿色、质地致密、生长缓慢的愈伤组织，不论有芽分化或无芽分化时，其甜菊糖苷含量均较高。在电镜下观察到，这两种愈伤组织细胞具有类似的超微结构特征：细胞高度液泡化；叶绿体发育成熟，光合膜系统结构发达，基质浓厚且含有质体小球；微体具有典型的晶格结构，常与叶绿体紧密相靠。黄色、质地致密、生长缓慢的愈伤组织中甜菊糖苷含量较低，其细胞内质体富含淀粉粒，只有少量分散的片层结构，有的质体甚至完全被淀粉粒所充塞。黄色、质地疏松、生长快速的愈伤组织中甜菊糖苷含量最低，其细胞内质体结构简单，片层稀少。质体的发育和液泡的分化与甜菊糖苷的积累密切相关。愈伤组织具有较高的甜菊糖苷含量在于愈伤组织细胞的组织化以及细胞的高度液泡化并具有发育成熟的叶绿体。

THE GROWTH AND DIFFERENTIATION OF CALLUS CULTURES OF STERIA REBAUDIANA IN RELATION TO THE STEVIOSIDE ACCUMULATION

Stevioside accumulation in callus cultures derived from Stevia rebaudiana leaf explants was studied during callus growth and differentiation. Increase in stevioside content was positively related to the organization of cells and greening of the cultures, and inversely to the callus growth. Shoot formation in calli was not essential for the synthesis of stevioside. The content of stevioside was highest in slow-growing, compact and green calli either with or without shoot formation. Electron microscope observation showed that these two kinds of callus cells were highly vacuolated and contained fully developed chloroplasts which had dense stromata and plastoglobuli. The microbodies containing crystal lattices were closely associated with chloroplasts. Slow-growing, compact, but yellow calli accumulated lowest stevioside, the plastido in cells of which contained many starch grains with few dispersed lamellae, and some plastids were even filled with starch grains. However, lowest stevioside content was found in fast-growing, loose and yellow calli in which the cell plastids were simple in structure and having only few lamellae. The results showed that stevioside accumulation was closely related to plastid development and vacuole differentiation, suggesting that the organization of callus cells with well development of vacuoles and chloroplasts caused highest stevioside content in slow-growing, compact and green calli.