[Comparison of presence of ascorbic acid and the appearance of ascorbate peroxidase activity in embryos of Avena sativa L]

Abstract

Avena sativa L. grains are devoid of ascorbic acid (AA) and of oxidative enzymes (AA oxidase and AA peroxidase), while both reducing enzymes (AFR reductase and DHA reductase) are present. AA biosynthesis in the embryos starts after 12-14 hours of germination and at the same time AA peroxidase activity is detectable. During the following 14 hours the AA peroxidase activity rises up to 28 nmoles/AA oxidated/min/mg/prot. Incubation of Avena embryos with GL (the last precursor of AA according to the Isherwood biosynthetic pathway), results in both earlier AA biosynthesis and enhanced AA peroxidase activity. A 4 hour treatment is enough to induce AA synthesis and AA peroxidase elicitation. These data suggest that the development of AA peroxidase activity is controlled by AA, but they are not sufficient to clarify how that happens. Probably AA induces the synthesis of specific m-RNAs or activates enzymic precursors present in the embryos but still not working.