Regulation of Medicago sativa L. somatic embryos regeneration by gibberellin A3 and abscisic acid in relation to starch content and α-amylase activity

Somatic embryo quality is an important factor decisive for the efficiency of somatic embryogenesis. Addition gibberellic acid (GA(3)) at a concentration of 1 mu M to germination medium improved the regeneration of alfalfa somatic embryos. Inhibitory effect of ancymidol, an inhibitor of gibberellin biosynthesis, on germination and conversion may indicate that those processes require endogenous GAs. Since fluridone, an ABA biosynthetic inhibitor, at a concentration of 1 mu M, had a slight stimulatory effect on germination of somatic embryos, it may be presumed that embryos contain a too high level of residual ABA after maturation phase (20 mu M ABA is used at that phase). The observed improvement of regeneration of somatic embryos by GA(3) was correlated with acceleration of starch hydrolysis through alpha-amylase activity enhancement by GA(3). In contrast, the inhibitory effect of ABA on the above processes was probably related to inhibition of alpha-amylase activity and, in consequence, to delayed starch hydrolysis. It is suggested that alpha-amylase activity can be considered a good marker of the quality of Medicago sativa L. somatic embryos.