Novel Carrot Embryo-forming System.

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We have developed a novel embryo-forming system in which carrot somatic embryogenesis takes place in a one-stage process from epidermal cells in the absence of 2,4-D,provided hypocotyl explants are incubated in a liquid MS medium containing 2,4-D for 12-24 hours. In addition, in this system, somatic embryos develop directly via formation of cluster cells by repeating division of organized epidermal cells with adhesion to explants, without dedifferentiation to callus and suspension cultured cells. Somatic embryogenesis occurred directly from carrot epidermal cells was observed using scanning electron microscopy.Epidermal cells peeled off from parent tissues were present as compressed cells and then expanded to become tubelar cells. Subsequently, tubular cells were regularly and horizontally divided to from linear cluster cells and then these cluster cells divided vertically to become enlargment. Swelling structure were formed by irregular and oblique division at places on linear cluster cells and then continued to divide to form small proembryos. Some cells which comprised surface of swelling structure and proembryos expanded to every direction to become covered on surface of structure. These expanding cells made probably put a layr of surface of structure and furthermore piled up cell layr to form from swelling to globular-stage embryo via small proembryo. These expanding cells were formed on surface of heart-stage embryo.