Callus begun from in vitro culture of immature embryos from two alloplasmic lines of maize was examined histologically to observe the influence of exogenous 2-4-D hormone concentration, saccharose concentration, and age of the embryos cultivated, on the induction of somatic embryos.

Meristem apex was observed in the callogenic mass only when the callogenic mass originates through scutellar development induced by the combination of 1 mg.L-1 of 2-4-D and 3% saccharose with embryos of up to ten days after pollination. At the same time examination of the callus through MEB shows an organised globular structure with isodiametric cells characteristic of the first stages of the embryogenic axis from scutellum.

In contrast, callus originating under other combinations shows meristematic points that give rise to aberrant roots afterwards. The observations prove that somatic embryogenesis can only be induced in the first stages of in vitro culture under the influence of exogenous auxin in the appropriate concentration. Later change in the auxin concentration provokes the manifestation of the totipotentiality of the cells that were induced before.
 

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