Seeds of Hymenaea courbaril L. have a storage polysaccharide that is mobilized after germination, when the first leaf is already photosynthetic. During reserve mobilization, the seedling has to coordinate two carbohydrate sources: photosynthesis and storage mobilisation. Both use sucrose to export carbon. To understand the allocation of carbon resources in the seedling, therefore, it is essential to study the catabolism of sucrose in the organs. In the present work, the low molecular weight carbohydrates were analyzed, as well as the activity of sucrose synthase and of the three isoforms of invertase in organs of Hymenaea courbaril L. seedlings along a day. The analysis was made each 6 hours, with an extra analysis at 2 am. Each enzyme had a characteristic variation pattern along the day, suggesting distinct and independent functions for each organ. The carbohydrate analysis showed higher concentration of sucrose in the sink-organs, while the cotyledons had high concentration of free monosaccharides. The existence of isoforms with distinct properties and cellular distribution varying in independent ways along the day suggests that these isoforms may have distinct physiological functions in the plant.
cotyledons; germination; invertase; sucrose synthase; seed
