Promotion of embryogenesis in cultured megagametophytes of Larixdecidua

In the summer of 1985, female gametophytic explants of Larixdecidua were cultured on LM medium containing 2,4-D (2.0 mg/L). In the subsequent growing season (1986), various concentrations of 2,4-D (0, 0.2, 2.0, and 20 mg/L) were used as media supplements and evaluated in material collected weekly from early June to late July. Optimal induction of callus and embryogenesis occurred at 2.0 mg/L 2,4-D and depended on collection date. Two kinds of callus were produced, a white embryogenic callus developed from explants from late June onwards, and a green nonembryogenic callus developed from middle to late July. Various concentrations of sucrose and sorbitol were tested in osmotically equivalent combinations together with the optimal level of 2,4-D (2.0 mg/L). The production of embryogenic callus was best on 3% sucrose and no sorbitol. Embryogenic callus developed from both chalazal and micropylar portions of the excised megagametophyte.