INFLUENCE OF SOME EXOGENOUS AMINO-ACIDS ON THE PRODUCTION OF MAIZE EMBRYOGENIC CALLUS AND ON ENDOGENOUS AMINO-ACID CONTENT

The effects of four exogenous amino acids (proline, glycine, asparagin e and serine) on the production of maize embryogenic callus and on its endogenous amino acid content have been investigated. For this purpos e, an established embryogenic line of Type 1 callus from the inbred W6 4Ao2 has been used. From the results it may be concluded that a concen tration of proline exceeding 6 mM is negative for the production of em bryogenic callus. When proline is eliminated from the medium, other am ino acids tested in certain concentrations yield a percentage of embry ogenic callus production that exceeds or equals that of proline. The e ndogenous free proline content in embryogenic callus is significantly higher than that in non-embryogenic callus regardless of proline prese nce in the medium. The only exception are the glycine-containing media , in which endogenous free alanine of embryogenic callus increases at the expense of endogenous free proline. This study suggest a positive role of endogenous free proline or alanine accumulation in the embryog enic callus production which might be related to an adaptation to the metabolic changes produced by in vitro culture and embryogenesis induc tion. Furthermore, these results indicate that treatments with amino a cids that are different from proline can be used to improve the effici ency of embryogenic callus production from well established maize call us cultures.