| Soluble sugars are important regulars in plant development and growth, gene expression. The changes of soluble sugars not only represent the degree of disturbance of the external environment in physiological level, but also indicate mutual transformation of various life cycle forms in substance distribution. In this study, the change of soluble sugars in Catharanthus roseus leaves, the growth and phenotype character were quantitatively and qualitatively analyzed respectively in different environments, in order to discuss the mechanism that soluble sugar response to external environmental condition, and the interaction between soluble sugars and the formation of C. roseus life cycle forms. The results of this study as follows:1. Under different soil humidity, the content of total soluble sugars is increasing in high drought stress (RWC=30%-35%). Analyze the content of glucose, fructose and sucrose respectively, we find that the changes of glucose and sucrose are obviously in high drought stress, the content of sucrose is 24.07mg/g FW which increases 52% compared with the control, but the content of fructose is not change during this treatment. Thus, during the high drought stress, sucrose and glucose have an important role in osmotic regulate. Sucrose and glucose act as antagonistic substance which response to the transformation of plant life cycle forms from vegetative growth to clone reproduction. In middle drought stress (RWC=40%-45%), sucrose acts as propagation-promoting substance inducing the transformation to sexual reproduction, acts as antagonistic substance changing the osmotic, and also acts as structure-building substance with glucose supporting energy and substance to sexual reproduction.2. Under the 40℃high temperature condition, the contents of hexose and sucrose highly increase in C. roseus leaves. In the fourth week of treatment, the content of sucrose is 1.616mg/g FW, increasing 1.051 mg/g FW compared with control 28℃, the content of hexose increases three times compared with control. High temperature promotes the transition from vegetative growth to procreative growth, sucrose and hexose act as structure-building substance supporting energy and substance to the sexual reproduction, sucrose also can act as propagation-promoting substance promote the transition of C. roseus life cycle.3. Under weak light intensity, the photosynthesis evidently decrease, which induces the descending of energy. The limited energy is distributed propagation-promoting substance and antagonistic substance in order to finish the changes between S to C. So the energy distributed to structure-building substance is decrease, and the content of hexose and sucrose largely decrease．In the third week of treatment,the content 0f hexose is 2．074 mg/g Fw in control,but in weak light condition,the content is just 1．531 mg/g FW．4．The treatment of exogenous ABA and GA,the changes of sucrose are obvious in C．roseus．In the fifth day of experiment,the content of sucrose increase 1．1 33 mg/g FW cornpared with control．Sucrose acting as alltagonistic substarlce interacts with ABA,they promote the reproductive growth of C roseus,Meanwhile,sucrose acts as structure-building substance providing energy and substance．Under the GA treatment,the vegetative growth of C.roseus is bloom；the repmductiVe growth is severely restrained．At this time,the content of sucrose in decrease in C.roseus leaves．but the content 0f hexose accumulates．Hexose acts as structure-building substance supporting energy and substance to the Vegetative growth,in order to response to the trailsition of C.roseus life cycle forms．...
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