The role of lipases in the germination of dormant apple embryos

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Abstract
Changes in the activity of alkaline and acid lipases were studied during the culture of embryos isolated from dormant apple (Pyrus malus L.) seeds. Light and treatment with gibberellins (GAs) and with AMO-1618, an inhibitor of GA biosynthesis, influenced the activity of both enzymes. In dark-grown embryos the activity of the alkaline lipase is stimulated by red irradiation and by treatment with GAs, particularly GA4, but is not increased after far-red irradiation or in the presence of AMO-1618. In light cultured embryos, it is inhibited by the latter compound. Germination of the embryos is affected by the various treatments in a similar manner as alkaline lipase activity. These results suggest that light stimulates germination of dormant apple embryos by promoting GA4 biosynthesis via the phytochrome system; GA4 increases the activity of alkaline lipase, the enzyme hydrolysing the storage lipids. Activation of acid lipase by the same factors is of a more complicated nature, light, GAs, and AMO-1618 generally causing a decrease in the activity of this enzyme.