Histological changes during direct somatic embryogenesis from immature zygotic embryo explants of Capsicum annuum L. cv. Sweet Banana

Direct somatic embryogenesis was initiated from immature zygotic embryo explants of Capsicum annuum L. cv. Sweet Banana. Globular embryonic structures were easily observed under a stereo-microscope after 14 days of culture on induction medium containing 2,4-D. These structures turned green 5-7 days after explants were transferred to germination or conversion medium devoid of 2,4-D, and then they germinated into plantlets about 3 days later. The origin and developmental sequence of somatic embryos were investigated using a resin infiltration and embedding technique. Periclinal cell division firstly began underneath the protoderm of the cotyledons of explant after 3 days of culture on induction medium. The number of cells obviously increased after 5-7 days of culture as a result of both periclinal and anticlinal cell divisions. Upon further culture on germination or conversion medium, other well known somatic embryo developmental stages, including heart-shaped, torpedo and cotyledonary stages were observed.