Histological Observations on Initiation and Morphogenesis in Immature and Mature Embryo Derived Callus of Barley (Hordeum vulgare L.)

Callus was induced from immature and mature embryos of barley (cv. Haruna Nijo) on Murashige and Skoog medium containing 2 mg l-1 2,4-D and 5 mg l-1 picloram, respectively. Paraffin sections (10 µm thick) were prepared for histology during callus initiation and plant regeneration. Meristems were regenerated from nodular compact callus (NC) derived from scutellar epidermis in immature embryos, whereas they were regenerated from NC derived from epidermal cells of leaf or coleoptile bases in mature embryos. Regardless of the explant source, regeneration was predominantly through organogenesis, although regeneration through somatic embryogenesis infrequently occurred. Thus, the callus induced from immature and mature embryos of barley was regarded as 'nodular compact' rather than 'embryogenic'.