Relationship of Cotyledon Number with Procambium Differentiation in Somatic Embryogenesis of Codonopsis lanceolata L

Embryogenic callus was obtained from cotyledonary explants of Codonopsis lanceloata on Murashige and Skoog's medium supplemented with 1 mg/L 2,4-D. Suspension cultures of the embryogenic calli were grown on a shaker at 100 strokes/min, and then the calli were subcultured for 2 weeks in 2,4-D-free medium to produce somatic embryo. In somatic embryos at the globular stage, cotyledon initials began to differentiate themselves in the near distal end of the procambial strand.