Abstract: Using immature embryos of soybean as explants, green structures and somatic embryoids were able to be induced on higher auxin-containing media. Genotypes, developmental degree of the embryos, origin of the explants and medium compositions all affected the occurrence of the structures and calli. After the green structures were transferred to high 2,4-D containing medium (30 mg/l) calli were reinduced. These calli were maintained on the same medium without being subcultured for 2 months and then transferred to lower hormone-containing media. After 2 weeks, a great number of new green structures in the same shapes were induced. It was shown that high level of 2,4-D played a unique role in lasting the morphogenesis ability of the cultures. When the green structure were cultured on low hormone-containing media they developed new leaves and formed leaf clusters while the apical did not develop. In order to stimulate the apical development the medium containing 2 mg/l GA3 and 0.1 mg/l IBA was used and some plantlets were obtained. The different effects of NAA and 2,4-D on the explants and calli were studied. Calli induced from the cotyledon of immature seeds (416 mm) had a regeneration ability stronger than that from the seedlings. The calli induced by use of the medium containing high concentration of 2,4-D (5–30 mg/l) have higher potentialities in producing green structures. In contrast, the calli induced by high concentration of NAA (10 mg/l) were highly root-morphogenetic. The explants and the calli cultured on the medium containing 5 mg/l 2,4-D could be maintained for a long term without being subcultured frequently.

Key words: Glycine max , Immature embryo, High concentration auxin, Plant regeneration