SEASONAL CHANGES IN METABOLISM OF SPRUCE LEAVES

Abstract

Sucrose, raffinose, pinitol, shikimic acid, and pungenin were isolated in crystalline form from leafy twigs of both Colorado spruce (Picea pungens Engelm.) and white spruce (Picea glauca (Moench) Voss) collected in winter. Raffinose and sucrose were the main sugars present in winter but raffinose disappeared in early spring and was not found again until autumn. Pungenin was also found in lowered concentrations in summer, and pinitol could not be crystallized from material collected in warm weather.Leafy twigs were harvested at different seasons and allowed to photosynthesize in the presence of C¹⁴O₂under constant conditions in the laboratory. Winter twigs were found to be convenient and efficient for the preparative biosynthesis of sucrose-C¹⁴and raffinose-C¹⁴. Hemicellulose was labelled much more rapidly than cellulose. The C¹⁴in the hemicellulose was concentrated in the glucose, little being found in the xylose.The relative rates of labelling of the sugars, pinitol, shikimic acid, pungenin, cellulose, and lignin showed some marked seasonal changes.