Morphotypes of friable embryogenic maize callus.

Friable, embryogenic callus cultures of maize are normally maintained as a heterogeneous mixture of various morphotypes in different stages of development (Fransz and Schel 1991). With stringent selection during subculture, three Type II callus morphotypes have been enriched and maintained. Cultured tissue segments from the three morphotypes referred to as "pre-embryogenic", "early embryogenic", and "late embryogenic" were analyzed using light and scanning electron microscopy. The results suggest a developmental relationship between the three morphotypes. Regeneration studies substantiated that all morphotypes were capable of regenerating through somatic embryogenesis.