Morphogenesis in callus tissue ofMedicago sativa: The role of ammonium ion in somatic embryogenesis

Abstract

Abstract. Exogenously supplied ammonium ion is critical to alfalfa morphogenesis in vitro. In alfalfa, the ability to induce the formation of either roots or somatic embryos provided an opportunity to examine the effects of ammonium ion on each pattern of morphogenesis. Somatic embryo formation required a minimum of 12.5 mM NH~ in regeneration medium for optimal expression. Root formation was inhibited by NH~ levels of 50 mM and above, and occurred in the absence of exogenous NH~. At high levels of NH~ somatic embryos were formed from ceils exposed to the root-inducing combination of hormones. This observation suggests that the growth regulators and exogenously supplied ammonium ion comprise an interactive system controlling the in vitro pattern of alfalfa morphogenesis.

Establishment of Embryogenic Potential of Economically Important Bulgarian Alfalfa Cultivars (Medicago SativaL.)

“…In their case 50 mg of the induced 45-50 days old callus was re-suspended in 3 types of liquid media, different in their content of ammonium and L-proline: B 5 II medium; Bsll 1 medium, containing NH4H2P04 and (NH4hS04 and Bsll2 medium, containing NH4H2P04, (NH 4 ) 2 S04 and L-proline. There are indications that a certain level of ammonium ions in the nutrient formulation is required for the expression of somatic embryogenesis in some leguminous species (39,14). Somatic embryos were induced, for example, with as little as 5mM ammonium in alfalfa (24).…”

Indirect somatic embryogenesis from transgenic immature leaf of safflower Carthamus tinctorius (Mohler, Roth, Schmidt & Boudreaux, 1967) (Asterales: Asteraceae)

“…The embryogenic induction and differentiation is requirement of NH 4 + was noticed by several other authors in different species and culturing systems (Walker and Sato, 1981;Meijer and Brown, 1987;He et al, 1989). Germinated, somatic embryos sprouted cotyledons with shoot poles and hypocotyls with root poles synchronously on semi solid medium containing GA 3 .…”

Somatic Embryogenesis and the Technology of Synthetic Seed

“…Such cultivars would be genetically uniform. Although excellent embryogenic culture systems exist for both alfalfa (e.g., Walker and Sato 1981) and orchardgrass (e.g., Gray et al 1984), a limitation to this application of synthetic seed technology is the low per-plant value and the low cost of existing seed. An intermediate use of synthetic seed for these crops may be to increase parental lines prior to establishment in open crossing blocks (McKersie et al 1989;Gray 1990a;Gray et al 1992).…”