CHANGES IN POLYAMINE METABOLISM DURING SOMATIC EMBRYOGENESIS IN PICEA-ABIES

The concentrations of free, conjugated and bound polyamines (putrescine and spermidine) and the activity of a key enzyme, [S-adenosylmethionine decarboxylase (SAMdc)], which participates in the biosynthesis of spermidine, were studied in embryogenic and non-embryogenic callus cultures of Picea abies (L.) Karst. When the calli were transferred on ABA (10 muM) containing maturation media, where proembryos in embryogenic callus develop to mature embryos, both tissues contained high levels of free and conjugated putrescine. After 5 days the putrescine levels decreased in both tissues and did not rise thereafter. The total spermidine level (free, conjugated and bound) was nearly four-fold higher in the embryogenic callus in comparison to the non-embryogenic tissue during the development of globular embryos in the embryogenic callus. In our cultures a positive correlation was found between spermidine concentration and SAMdc-activity. If methylglyoxal bis(guanylhydrazone) (0.1 mM), an inhibitor of SAMdc, was added to the nutrient medium of embryogenic cultures, the levels of total spermidine decreased to nearly half, although further development of somatic embryos was not inhibited.