Direct differentiation of somatic embryos on different regions of intact seedlings of Azadirachta in response to thidiazuron

Direct differentiation of somatic embryos occurs in high-frequency and at high density in response to 1.0 μM TDZ, on different regions—hypocotyl, epicotyl, cotyledonary-node, cotyledons and leaves—of intact seedlings of Azadirachta. One-week-old seedlings on this medium exhibited stress symptoms as visible by the loss of root formation and reduction in the elongation of hypocotyl and epicotyl. Globular somatic embryos were more abundant on hypocotyl, epicotyl, stem tip and leaves. The arrest of embryos at this stage was possibly due to their presence in high density. Well-developed somatic embryos were present on the cotyledons and the cotyledonary-node. These embryos on isolation and transfer to hormone-free medium regenerated readily to form plantlets. The possible role of stress in thidiazuron-induced somatic embryo formation is discussed.