Somatic Embryogenesis in Cephalotaxus harringtonia Embryo-Megagametophyte Co-culture

Abstract

Somatic embryogenesis was initiated from Cephalotaxus harringtonia (Forbes) K. Koch embryo culture. Explants consisted of embryo and megagametophyte halves both cut longitudinally. They were removed aseptically from mature seeds and grown together on a solid Murashige and Skoog modified medium supplemented with 5 mg ▪ l −1 2,4-dichlorophenoxyacetic acid. Embryogenic cultures started from callus after three or more months on the primary medium. The embryogenic callus originated from the suspensor region of the embryo. All chromosome counts made in the cells of the embryonic structures demonstrated a diploid stage, which suggest that they originated from zygotic embryo tissue. The early stages of somatic embryogenic development were achieved, i.e., formation of small clusters consisting of an embryonal region made up of isodiametric meristematic cells. A more advanced stage was reached in some cultures in which the distal embryonal end of the embryo appeared smooth and opaque. The ultrastructural characteristics of the embryos, the two types of embryo cells, embryonal and suspensor cells, as well as their contents were similar to those already reported in the case of somatic embryogenesis of other conifers.