NON-STRUCTURAL CARBOHYDRATE PARTITIONING IN Erythrina velutina Willd. DURING SEED GERMINATION AND SEEDLING ESTABLISHMENT
Amylases, mulungu, source-sink relation, soluble sugars, starch
Seed germination and seedling establishment are critical processes for plant communities, as high mortality takes place at these initial steps of the plant life cycle due to the exposure to biotic and abiotic stresses. Taking into account the central role of carbon metabolism in the heterotrophy-autotrophy transition, closely related to survivorship, this work aims to investigate the partitioning of non-structural carbohydrates in the different organs of Erythrina velutinaWilld., a pioneer species from the Caatinga, during seed germination and seedling establishment. Seeds from ten mother trees were scarified, disinfected, soaked in distilled water, sown in rolls of Germitest® paper and kept under controlled conditions for 9 days. Then, the seedlings were transferred to hydroponics in distilled water and grown in a greenhouse for 12 days. The collections were carried out at discrete physiological stages, including imbibed seed, radicle protrusion, hypocotyl emergence, plumular hook opening, and emergence of cordiform leaves, first trifoliolate leaf and second trifoliolate leaf. The seedlings were divided into cotyledons and other parts, according to their appearance during the different stages. Ao longo do estabelecimento, houve diminuição progressiva de massa seca nos cotilédones, sendo transferida para os órgãos dreno, especialmente a parte aérea, segundo o decréscimo da relação raiz/parte área ao longo do experimento. Total soluble sugars, non-reducing sugars and starch were accumulated in the root and hypocotyl during the initial stages and the content of these compounds increased in the leaves at the late stages of establishment. Amylase activity was higher in the shoot than in the root in the course of the experiment. These results show that E. velutina massively utilized non-structural carbohydrates to axis growth at early establishment and these compounds may have been accumulated in the leaves at late establishment as a result of photosynthetic activity.