The embryonic axis controls lipid catabolism in cotyledons of apple seeds during germination

Abstract

Activities of alkaline lipase (AlkL, EC 3.1.1.3), isocitrate lyase (ICL, EC 4.1.3.1), glucose 6‐phosphate dehydrogenase (G6PDH, EC 1.1.1.49) and pyruvate kinase (PK, EC 2.7.1.40) were determined in embryos of apple ( Malus domestica Borb. cv. Antonówka) during culture in darkness or at 12 h photoperiod; in both cases either in the presence of gibberellin A 3 (GA 3 ) or AMO 1618 (inhibitor of GA synthesis). AlkL and ICL were stimulated by light and GA 3 ; light stimulation was reversed by AMO. G6PDH and PK were not affected by culture conditions. Almost all the activity of all enzymes was found in the cotyledons; only PK was distributed between axis and cotyledons. GA‐like activity was found almost exclusively in the embryo axis. Cultured isolated cotyledons lost their sensitivity to light and AMO, but AlkL and ICL were still stimulated by GA 3 . Translocation of GA from axis to cotyledons during the culture of embryos is postulated.