Somatic embryogenesis refers to the remarkable ability of nonzygotic plant cells (including haploid cells) to develop through characteristic embryological stages into an embryo capable of developing into a mature plant. Somatic embryogenesis is an expression of totipotency and the associated differential gene expression. Somatic embryos may be produced in nature in certain plant species as a form of apomixis known as adventitious embryony. Somatic embryogenesis in plants usually refers to the induction of somatic embryos in vitro, first demonstrated by both Steward and Reinert in 1958. Research into somatic embryogenesis has intensified as plant regeneration in vitro has come to be widely utilized in transformation and somatic hybridization. This article emphasizes basic procedures and key variables for inducing somatic embryos, their developmental biology, and their mechanism of induction. Somatic embryogenesis may be direct or indirect. Direct somatic embryogenesis does not require a callus phase to induce somatic embryos from the explant. Indirect somatic embryogenesis has been most extensively studied and is widely used in transformation and somatic hybridization.
Encyclopedia of Plant and Crop Science p. 1165-1167