It was found that the temperature optimum for apple (Malus domestica Borb.) seed acid lipase is the same as that for seed after-ripening process. The activity of the enzyme occurs between the 40th and 70th days of stratification, whereas the activity of alkaline lipase very low at that time appears about 20 days later. The changes of both enzyme activities were also studied during dark and light culture of embryos isolated from seeds after different times of stratification. Only the alkaline enzyme activity is under the control of light. It was concluded that essentially the same process, i.e. the hydrolysis of reserve fats is catalysed by two different enzymes: acid lipase acting during the cold-mediated breaking of embryo dormancy and alkaline lipase acting during the germination of dormant embryos, thus being under light control.

No 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 A3 (GA3) or AMO 1618 (inhibitor of GA synthesis). AlkL and ICL were stimulated by light and GA3; 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 GA3. Translocation of GA from axis to cotyledons during the culture of embryos is postulated.

No abstract

The activity of acid lipase and the level of gibberellin A4 (GA4) were determined in apple embryos excised from seeds after different time periods of stratification and subsequently cultured in darkness at 4°C or at 25°C. Enzyme activity and GA4 content were higher at 4°C. Exogenous gibberellin stimulated lipase activity, while AMO‐1618, an inhibitor of gibberellin biosynthesis, inhibited, to the same degree, both the enzyme activity and the GA4 accumulation. The involvement of GA4 and lipolytic enzymes in cold‐mediated removal of embryonal dormancy has been discussed and compared with the role of these two factors in light‐stimulated germination of dormant apple embryos, described earlier (Smoleńska and Lewak 1974).