Ascorbic acid changes the pattern of purine metabolism during germination of white spruce somatic embryos

It has previously been shown that exogenous applications of ascorbic acid ( AA) increase the conversion frequency of somatic embryos of white spruce (P icea glauca (Moench) Voss). To determine whether ascorbic acid alters purin e metabolism during the early phases of embryo germination, the relative ra tes of purine salvage and degradation were investigated by following the me tabolic fates of exogenously applied [8-C-14]adenine, [8-C-14]adenosine, an d [8-C-14]inosine, and the activities of several key enzymes. We demonstrat ed that both the salvage and the degradation pathways operate during germin ation. Specifically, adenine and adenosine were mainly salvaged to nucleoti des and nucleic acids, whereas an appreciable amount of inosine was degrade d to CO2 and ureides. Comparisons of purine metabolism between control and AA-treated embryos showed that exogenous applications of ascorbic acid enha nced the ability of the embryos to take up adenine and adenosine throughout the germination period. Furthermore, the higher enzymatic activities of ad enosine kinase and adenine phosphoribosyltransferase were responsible for t he larger proportion of adenine and adenosine being salvaged in AA-treated embryos compared with control embryos. Thus, there was a positive correlati on between the ability to anabolize purine precursors and successful embryo conversion.