Abstract: Endogenous ABA levels of carrot (Daucas carrota L. ) somatic embryos and their organs were assayed under different sucrose concentration in MS media using ELISA. The results show that endogenous ABA level increases during the development of somatic embryo and reaches the highest at cotyledonary stage. ABA levels of somatic embryo vary little among different treatments at the early developing stage and more significantly when cotyledonary embryos grow bigger. ABA level decreases obviously once the regulated embryos is de-regulated in culture. The content of ABA in the regulated embryos and their organs maintain relatively unchanged in two months. These results imply that sucrose concentration in media induces the changes of ABA levels in the somatic embryo, and these changes are dependent to the different developing stages. High level of ABA in medium can maintain the embryo quiescence. Some difference still exist between the effects of exogenous ABA and those of high sucrose concentration on carrot somatic embryos. By and large, ABA probably acts as an important signal-mediated factor during the signal transduction of sucrose regulation on the development of somatic embryos in carrot.

Key words: Carrot, Somatic embryo, Regulation culture, ABA, Sucrose signal