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  • Author or Editor: Yehoshua Saranga x
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Somatic embryogenesis was induced from internodal callus of `Scania', `Improved White Sim', and `Sandra' carnation (Dianthus caryophyllus L.). The optimum protocol for the induction of somatic embryogenesis included initiation of callus in liquid basal Murashige and Skoog medium supplemented with 3.0 μm 2,4-D followed by transfer to liquid basal medium lacking 2,4-D for embryo development. Somatic embryos originated from single cells and early embryonic development proceeded conventionally (i.e., via globular, heart-shaped, and torpedo stages), but clearly developed apical or root meristems were not always formed. A few embryos developed into seedlings and were acclimatized to ex vitro conditions. Chemical name used: 2,4-dichlorophenoxyacetic acid (2,4-D).

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Desiccation tolerance of somatic embryos is a key factor for production of dry synthetic seeds. In celery (Apium graveolens L.) desiccation tolerance can be enhanced by optimization of culture duration, ABA application, or sucrose concentration in the embryo production medium. Morphologically mature embryos cultured for 10 days have shown higher desiccation tolerance then those cultured for 8 days, indicating that biochemical changes occur without any noticeable morphological changes. Application of ABA (1 μM) for the last two days of the embryo production cycle was critical for inducing desiccation tolerance; ABA application for the last four days had some additional beneficial effect. Desiccation tolerance was further enhanced by increasing the sucrose concentration of the embryo production media from 3% to 7% for the last two days. Increased desiccation tolerance achieved with optimal harvest timing and ABA application were associated with increased endogenous proline and aminobutyrate, and reduced glutamine.

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Density changes associated with developing zygotic embryos of loblolly pine (Pinus taeda L.) and somatic embryos of celery (Apium graveolens L.) were determined using sucrose gradients. Continuous sucrose gradients were used to evaluate relative density of loblolly pine embryos from July 25, when embryos could be microscopically observed, to November 7, 1988. Embryos density declined during development with a maximum (51% sucrose equivalent or 1.2331 g/ml) at first sampling and then remain relatively constant (10% sucrose equivalent or 1.0306 g/ml) after day 49. Density changes were inversely related to embryo length.

Celery somatic embryos, cultured for 6, 8, 10, or 12 days were separated with sucrose solutions varying from 9 to 16% in 1% intervals. Embryos were classified as overmature (expanded cotyledons), mature (torpedo), and immature (globular). The number of low density embryos increased from 6 to 12 days. The highest conversion to normal seedlings after desiccation for 48 hr at 90% relative humidity was obtained with overmature and mature embryos, but some immature somatic embryos also survived. Maximum conversion was obtained from embryos with density equivalent of 12% to 14% sucrose (1.0448 g/ml to 1.0531 g/ml) at days 10 and 12.

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