Early Events in Embryogenesis

Abstract

Plants, as compared to animals, are characterized by a great flexibility in their ability to differentiate. This flexibility is manifested, in vivo, in the capacity to generate and regenerate parts of the organism and, in vitro, with the acquisition of totipotency. This characterization of general nature is not applicable as such to all plant species. Cumulative work of many years in plant tissue culture shows that primary explants of various types (hypocotyls, cotyledons, leaves, roots, etc.) respond to synthetic media supplemented with auxins, typically 2,4dichloro-phenoxyacetic acid (2,4-D) and cytokinins (dispensable in some systems) by dedifferentiating the tissues so treated. However, the acquisition of morphogenetic capacity can occur with greater or lesser ease in the different species, or even, within a species, according to the genetic background of the varieties.