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SummaryEmbryogenic callus (EC) was initiated from inner tissue (IT) of protocorm-like bodies (PLB) of Cymbidium orchid cultured on Murashige and Skoog (MS) media supplemented with 1-naphthaleneacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D). EC was obtained within 15 days on a MS medium containing 2 mg• liter -1 NAA or 0.5 mg • liter -1 2,4-D which was the most effective among the concentrations tested. When EC were transferred to a hormone-free MS medium, they produced protocorms within one month and complete plants in another 3 months. In contrast, the EC, in the presence of BA or NAA, produced light green, hairless, string-like structures in one month. These string-like structures grew 2 to 3 cm in length and died within three months. IT produced no callus in hormone-free MS medium or in a medium to which BA and NAA were added. After 5 days of culture, with NAA or 2,4-D, a small mass of EC differentiated from the parenchyma cells of the vascular bundle on the basal cut end of IT sections. These ECs produced proembryoid-like structures after 10 days of culture; they became globular embryos 5 days later. The globular embryos differentiated into protocorms and plantlets after being transplanted to the hormone-free MS medium. These findings demonstrate that Cymbidium plantlets can be obtained from IT of PLB through somatic embryogenesis by manipulating the culture conditions.

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The embryogenic capacity of seven cucumber (Cucumis sativus L.) cultivars was examined by tissue culture of cotyledon, young first-leaf, and internode explants. Somatic embryogenesis frequencies differed significantly among the tested cultivars, and `Fushinarimidori' produced the highest number of embryos from either cotyledons or young first leaves. Cotyledon- and first-leaf-derived calluses produced more embryos than calluses from internodes. Somatic embryos were induced from `Aonaga F1' internodes. With relatively high sucrose levels (6% and 9%) in the initiation medium, the frequency of embryogenic callus formation from `Fushinarimidori' cotyledon explants was >90%. The highest yield of somatic embryos occurred in cultures initiated with high sucrose levels (9% or 12%), although 12% sucrose inhibited callus formation and growth. Somatic embryos germinated in a basal liquid medium supplemented with 0.5% activated charcoal, and they developed into well-shaped, healthy plantlets on semisolid medium with 1% sucrose.