Recent Advances in Conifer Somatic Embryogenesis

Somatic embryogenesis of coniferous species is used both as a means of propagation andas a valuable model system for investigating the structural, physiological, and molecular eventsoccurring during embryo development. The whole embryogenesis is composed of three steps: induc-tion and proliferation of embryogenic tissue, somatic embryo maturation, and somatic embryo germi-nation and conversion. In past, attempts for improving the whole embryogenesis procedure weremade almost during the maturation stage, because of the assumption that successful regenerationwould be related to treatments provided during the development of the embryos. However, in the lastseveral years, studies demonstrated that the early events in embryogenesis were also crucial for thecompletion of the overall embryogenic program, implemented by physiological, biochemical, andmolecular studies. Manipulation of the culture conditions early in the process can increase bothnumber and quality of the embryos. Furthermore, adjusting the medium can also enhance germinationand conversion frequencies of somatic embryos matured. These new findings are important forimproving induction and conversion frequencies in conifer somatic embryogenesis.