Nature and utilization of seed reserves during germination and heterotrophic growth of young sugar beet seedlings

The seed reserves of sugar beet (Beta vulgaris L.) are starch, located exclusively in the perisperm, and lipids, proteins and a small quantity of soluble sugars, located mainly in the cotyledons. It is shown that lipids are the main respiratory substrate used during germination whereas starch and remaining lipids are only hydrolysed after root extrusion, to sustain root and hypocotyl growth. By removing the perisperm during imbibition, it was demonstrated that lipids and proteins alone are sufficient for viable seedling development, though such seedlings grew less than those developing in the presence of perisperm. The utilization of seed reserves was followed during seedling development in the dark in various organs. At 20 degrees C, the reserves were sufficient for 8 d of growth in the dark, the hypocotyl attaining a length of 5 cm. Specific problems relating to field establishment of sugar beet are discussed in relation to these results.