PROLIFERATION AND PLANT REGENERATION FROM THE NODAL REGION OF ZEA MAYS L. (MAIZE,GRAMINEAE) EMBRYOS

Immature embryos of Zea mays L. (maize), cultured on Murashige and Skoog's medium containing 2,4-dichlorophenoxyacetic acid (2,4-D, 0.25–1.0 mg/l) and sucrose (3, 6 and 12%), produced a narrow ridge of tissue in the nodal region of the embryo axis, opposite the scutellum. Only those embryos which were placed with the scutellum in contact with medium showed such a response. The ridge of tissue further proliferated and formed a compact and opaque callus that appeared similar to the scutellar callus. Morphogenesis took place on media containing low concentrations of both 2,4-D and sucrose. Plant regeneration was achieved and is interpreted to take place by the precocious germination of somatic embryos. It is suggested that the ridge of tissue formed at the node may represent an evolutionarily extinct epiblast of the maize embryo and may be cotyledonary in nature.