There are two types of embryogenesis in plants: zygotic and somatic. Recently, some new tissue culture systems of somatic embryo formation have been established in Arabidopsis thaliana. Studies that use these somatic embryo induction systems together with classical tissue culture systems of carrot somatic embryos have shown that some embryogenesis-related genes (LEA genes, SERK, AGL15, BBM, LEC1, FUS3 and ABI3) were expressed in the same manner in both zygotic and somatic embryogenesis. ABA signal transduction in the late stage of embryogenesis was also shown to be common in both types of embryos. These findings showed that somatic and zygotic embryogeneses are physiologically and molecularly similar, and that tissue culture systems for somatic embryogenesis can be practically used to study the mechanism of plant embryogenesis. The somatic embryo tissue culture systems will enable the mechanism of plant embryogenesis to be understood, thereby providing much knowledge in this field.