Woong Young Soh

Regenerative ability of somatic single and multiple embryos from cotyledons of Korean ginseng on hormone-free medium

Abstract Cotyledon explants of Korean ginseng (Panax ginseng C. A. Meyer) produced somatic embryos directly on growth regulator-free medium. Somatic embryos developed as either multiple or single-state forms, depending on the degree of maturity of the cotyledons. Cotyledon explants from midmature zygotic embryos formed multiple embryos, while cotyledons from fully mature zygotic embryos formed single embryos. Somatic single embryos regenerated into normal plantlets with both roots and shoots, while multiple embryos did not produce roots but regenerated only into multiple shoots. In full-strength MS basal medium, the root growth of plantlets derived from single embryos was weak compared to that of shoots. Deletion of ammonium nitrate from the MS medium promoted the root growth of the plantlets. The ginseng plants with well-developed shoots and roots regenerated from single embryos were successfully acclimatized in a greenhouse when they were planted in soil.

Developmental and structural aspects of somatic embryos formed on medium containing 2,3,5-triiodobenzoic acid

Abstract Cotyledon explants of ginseng (Panax ginseng C.A. Meyer) zygotic embryos produced somatic embryos at a high rate (68%) on medium without any growth regulators. Under this culture condition, apparent polar somatic embryogenesis occurred near the basal-excised portion of the cotyledons. When the cotyledon explants were cultured on medium containing 2,3,5-triiodobenzoic acid (TIBA), an auxin polar-transport inhibitor, the frequency of somatic embryo formation markedly decreased and was completely inhibited on medium containing 20 µM TIBA. On medium containing 5–10 µM, somatic embryos developed sporadically on the surface of the cotyledons and had a normal embryo axis but jar-shaped cotyledons. Embryos with jar-shaped cotyledons were also observed to occur at a high frequency when the early globular embryos formed on hormone-free medium were transferred to medium containing 20 µM TIBA. From these results, it was deduced that endogenous auxin in the cotyledon explants plays an important role in the induction of somatic embryos and that the cotyledon development in somatic embryos is also related to the polar transport of endogenous auxin.

Somatic embryogenesis and plant regeneration from suspension cultures of Acanthopanax koreanum Nakai

Abstract High-frequency somatic embryogenesis was achieved from an embryogenic cell suspension culture of Acanthopanax koreanum Nakai. Stem segments were cultured on Murashige and Skoog (MS) medium containing auxins and cytokinins. Opaque and friable embryogenic callus formed on MS medium with 4.5 µm 2,4-dichlorophenoxyacetic acid (2,4-D) and 2.0 µm kinetin or zeatin, but was highest on medium containing 4.5 µm 2,4-D alone. Embryogenic calli were transferred to MS liquid medium containing 4.5 µm 2,4-D and maintained by subculture at 2-week intervals. Initiation of somatic embryogenesis and development up to the globular stage from embryogenic cell clumps occurred in medium containing 0.45 µm 2,4-D, whereas maturation and germination of somatic embryos occurred in MS medium lacking 2,4-D. Cytokinin treatment suppressed the normal growth of embryos, but stimulated secondary somatic embryogenesis from the surfaces of primary embryos. Plants from somatic embryos were acclimatized in a greenhouse.

Effect of plumule and radicle on somatic embryogenesis in the cultures of ginseng zygotic embryos

Immature zygotic embryos of ginseng produced somatic embryos on MS medium without growth regulators. However, in the culture of mature zygotic embryos, excision of the embryo was required for somatic embryo induction. Somatic embryos formed only on excised cotyledons without an embryo axis or on excised embryos without the plumule and radicle of the axis. This observation suggests that the axis tip of the embryo might suppress somatic embryo production although the cotyledon tissues have predetermined embryogenic competency. To clarify the role of the embryo axis on somatic embryo formation, excised plumules or radicles were placed in direct contact with the basal cut-ends of cotyledons. The adhesion of plumules or radicles highly suppressed somatic embryo formation from cotyledon explants. When an agar block containing exudate from excised plumules or radicles was placed in contact with the cut end of the cotyledon, a similar inhibition was observed. These results suggest that embryogenic competence is suppressed by endogenous inhibitors present in the axis tip of the zygotic embryo.

Plant regeneration through somatic embryogenesis from suspension cultures of Allium fistulosum L.

Abstract Green callus was obtained from the surface of embryogenic yellow callus which was induced from Allium fistulosum floret tissue on MS agar medium containing 0.5 mg/l 2,4-D and 0.5 mg/l BA. The initiation of green callus was significantly promoted by 0.5–1.0 mg/l BA supplement in culture medium. After the cell clumps developed from green callus were transferred to MS liquid medium supplemented with 0.1 mg/l of 2,4-D, proembryos formed. The proembryos put through a stainless sieve developed into synchronous somatic embryos, and these somatic embryos matured in MS liquid medium either without growth regulators or containing 0.1 mg/l of zeatin and 0.1 mg/l of ABA. Plantlets developed from mature embryos in MS medium either without growth regulators or containing 0.1 mg/l BA, and they were regenerated to plants in pots.

Somatic embryogenesis and plant regeneration in cotyledonary explant cultures of Chinese cabbage

Cotyledonary explants of Chinese cabbage were cultured on Murashige and Skoogs medium supplemented with various concentrations of 2,4-dichlorophenoxyacetic acid. Up to 20% of the cotyledonary explants produced somatic embryos with or without intervening callus production. Explants became more competent as the age of the source seedlings increased up to 8 days, but cotyledonary explants from 10-day-old seedlings were not responsive. Upon transfer to MS basal medium most of the somatic embryos developed into plantlets. Plantlets were transplanted to potting soil and grown to maturity in a phytotron. Among three cultivars used, only cotyledonary explants of ‘Top Salad’ were capable of producing somatic embryos.

High frequency somatic embryogenesis and plant regeneration in tissue cultures of Codonopsis lanceolata

Culture conditions for high frequency somatic embryogenesis and plant regeneration from cotyledonary explants of Codonopsis lanceolata are described. The maximum induction frequency of somatic embryos from cotyledonary explants was 80% on Murashige and Skoog (MS) medium containing 6% sucrose with 1 mg/l 2,4-dichlorophenoxyacetic acid and 10% coconut water. Upon transfer onto MS basal medium containing 3% sucrose, most somatic embryos developed into plantlets.

Somatic embryogenesis and plant regeneration in immature zygotic embryo, ovule, and anther filament cultures of Chinese cabbage

Abstract Immature zygotic embryos, ovules, and anther filaments of Chinese cabbage were cultured on Murashige and Skoogs (MS) medium supplemented with 1 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D). Up to 80% of the zygotic embryos, 17% of the ovules, and 13% of the filaments produced somatic embryos with or without intervening calli. Upon transfer to MS basal medium, most of the somatic embryos developed into plantlets. Plantlets were transplanted to potting soil and grown in a phytotron.

Morphological and anatomical variations ofCajanus cajan (Linn.) huth raised in cadmium-rich soil

Different concentrations of cadmium in the growing media affected morphological parameters ofCajanus cajan. Over time, the amount of increase in shoot and root lengths, number of branches and leaves per plant, single and total leaf areas, and dry mass of leaves, was significantly lower for treated plants compared with controls. The root-shoot length ratio, which varied little over time, was relatively low for the treated plants. Although dry mass of both stems and roots increased, the rates were considerably low under Cd stress. The root-shoot dry mass ratio in the controls was highest during flowering and lowest in the post-flowering stage, but continually declined over time for the stressed plants. Compared with the controls, treated plants had fewer pods, with the number decreasing as the Cd concentration increased. Cd content was greater in roots than in stems or leaves, and leaves had greater amounts than did stems at higher doses. For all plants, the width and density of vessel elements and the length of fibers in the wood of stems and roots increased with plant age. However, the rate of increase was generally lower in the treated plants, the difference being more pronounced with higher doses of Cd. This indicated a reduced ascent of sap and, hence, less available water for tissues in treated plants.

Effect of ammonium ion on morphogenesis from cultured cotyledon explants ofPanax ginseng

Cotyledon expiants ofPanax ginseng were cultured on modified Murashige and Skoog medium with various concentrations of NH4C1 and KNO,. Morphogenesis such as somatic embryo, embryogenic callus, or adventitious root formation from cotyledon expiants differently occurred according to the concentrations of NH/ and NO3. Somatic embryos were actively formed in a moderate concentration of NH4+ (20 mM) in combination of NO3, but in a high concentration of NH4+ (60 mM), only embryogenie calli were formed. In little or no NH4+, adventitious roots were formed at a high rate. The influence of NO3 on those morphogenesis was slight but combination of NO3 with NH4+ was indispensable since the cotyledon expiants were necrotized on medium containing only NH4+ as a nitrogen source. Histological observation revealed that somatic embryo and embryogénie callus formation occurred from the same origin (cotyledon epidermis), whereas, adventitious roots were originated from the cells near vascular strands.