Metabolismo de lipídeos, sacarose e antioxidante durante a germinação e desenvolvimento inicial de plântulas de seringueira (Hevea spp)

Abstract

The rubber tree (Hevea spp) is known as a potential species of latex. Little attention is focused on their seeds, since they can be used in the production of rootstocks for the implementation of new seringals and biofuel, in addition to being appreciated for human consumption in flours, supplements, cosmetics. The objective of this study was to evaluate the behavior of some enzymes involved in the metabolism of lipids, sucrose and antioxidants in order to increase knowledge about germinative aspects and initial development of rubber tree seedlings. The seeds used were collected from standing trees. The following stages of development were evaluated: quiescent seed (SQ) - shortly after dehiscence; "White point" (PB) - 9 days after sowing (DAS); "Spider's paw" (PA) - 13 DAS; "Palito" (PAL) - 18 DAS and leaf initiation (IF) - 25 DAS. 100 seeds and / or seedlings were collected at each stage and the following evaluations were performed: water content, dry matter, lipid content and histological analysis of the lipid bodies present in the endosperm. The enzymes analyzed were: acid invertase of the vacuole (IAV), acid wall invertase (IAP), cytosol neutral invertase (INC), embryonic axis, cotyledon, endosperm, almond, root and shoot. The enzymes: isocitrate lyase (ICL), lipoxygenase (LOX), catalase (CAT), glutathione peroxidase (GPX) and superoxide dismutase (SOD) were also analyzed by electrophoresis technique in cotyledon, endosperm, almond, root and shoot. Expression analysis was performed using ImageJ® software. The experimental design was completely randomized using the SISVAR software with analysis of variance based on the comparison of means by the Scott-Knott test, with a 5% probability. The highest content of lipids and dry matter was evidenced in SQ, this behavior is justified, since this is quantitatively the main reserve compound of the seed. Dry matter of the endosperm was significantly consumed during germination while the embryonic axis and cotyledons grew. The maximum degradation of lipids and sucrose synthesis occurs in the endosperm in PB. IAV activity was more pronounced in mature tissues. The activity of IPA was higher in developing tissues because this enzyme is characteristic of active growth zones. The activity of INC is relatively lower than acidic invertases, since it is an enzyme expressed in tissues aiming at the maintenance of carbohydrates. Another important finding is the presence of invertebrates in SQ, suggesting that these enzymes are pre-existing, since they are important during seed development. The expression of ICL in SQ can be derived from the seed formation process. On the other hand, the presence of LOX stresses the stress conditions that the tissues may have passed during germination. The high activity of CAT and GPX in SQ suggest that these enzymes come from the seed formation process and the SOD activity was superior to those of CAT and GPX as it is the first cell detoxification barrier. The increase in SOD activity during the germination process indicates the good hydration of these tissues, reducing the formation of reactive oxygen species.