||Histological Observation of the Somatic Embryogenesis in Dieffenbachia 'Anna'
Shen, Rong–Show ,
Jian, You–Lin ,
Lee, Yung–I ,
Huang, Kuang–LiangMiyajima, Ikuo
6 , 2016-02-29 , Faculty of Agriculture, Kyushu University
In this study, a procedure for the histological observation of the somatic embryogenesis in Dieffenbachia 'Anna' was developed. Thin slices of secondary somatic embryos (SSEs) were used as explants. Somatic embryogenesis tended to be derived from a single cell. Upon further differentiation, the single cell became an embryogenic cell mass, and somatic embryos (SEs) subsequently formed under the influence of 3, 6–dichloro–2–methoxybenzoic acid (dicamba) and 1–phenyl–3–(1, 2, 3–thiadiazol–5–yl) urea (TDZ). The cytological origin and early proembryoid differentiation process were initiated after 6 days of culture. A single embryogenic cell initiated asymmetric cell division to form an apical cell and basal cell. A two–celled proembryo subsequently developed from the basal cell, forming a three–celled proembryo. After 9 days of culture, the apical cell underwent anticlinal division, and prior the two cells of periclinal division to form a T–shaped four–celled proembryo. After 12 days of culture, the cells continued to divide and formed an eight–celled proembryo. After 15–18 days of culture, 8–10 cells formed a rudimentary proembryo, revealing the primary structure of the embryo. After 24 days of culture, a 16–celled proembryo was formed. The multicellular embryoid had formed within the explants, which gradually emerged to the surface of the explants. Each embryoid exhibited a thick cell wall, isolated with the surrounding cells from the embryonic base of the suspensor construction. After 27 days of culture, the proembryo emerged from the explant surrounding, and the early globular embryoid with protoderm. After 12 weeks of culture, the explants in the original medium formed embryoid clusters with various developments were visible. Histological observation showed that the globular embryos separated from the explants, with distinct protoderm and Y–shape closed procambium. During the development of the somatic embryos, an asynchronous phenomenon was observed in the mature embryo stage of the scutellum and coleoptilar embryos, but not when the mature somatic embryos converted to emblings.