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.
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.
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