Caracterização morfológica e mobilização de ácidos graxos durante a germinação e pós-germinação de hevea spp

Abstract

Hevea species provide latex, whose physicochemical properties are not synthetically replicable. Most of the studies related to rubber trees, especially involving H. brasiliensis, are focused on genetic improvement increase latex production and investigation of its physicochemical and biological properties. There are few studies involving seeds and seedlings of this genus, as well as its biotechnological potential. Understanding the morphophysiology of seeds can not only elucidate the botanical characteristics, but also provide information that can be used for the genetic improvement of the species and for the production of certified seeds. Therefore, the objective of this work was to investigate the morphology of the initial establishment of seedlings and the mobilization of fatty acids during germination and post-germination of H. brasiliensis, H. guianensis and H. spruceana. Seeds of H. brasiliensis were collected at Inpa/Campus I and III, while those of H. guianensis were collected at Reserva Florestal Adolfo Ducke and in a privately owned forest fragment located in Bairro Tarumã. In turn, H. spruceana seeds were collected at the Zoobotanical Park and Embrapa Rio Branco. The experiments were performed at the Laboratory of Plant Physiology and Biochemistry (LFBV/Inpa). Asepsis was carried out by washing in running water followed by immersion in 1.5% sodium hypochlorite for five minutes and triple washing in distilled water. The biometry of the quiescent seeds was done with the aid of a caliper. For the morphological characterization and evaluation of the mobilization of the lipid reserve experiments, the phases of quiescent seed (QS), radicle emission (RE), roots (RS) and eophylls (EO) were chosen. To the oil extraction, hexane was used as a solvent in the proportion of 3 mL for 100 mg of flour in an ultrasonic washer, followed by centrifugation for five minutes at 200 x g at 27 ºC. The samples were esterified by adding 2 ml of 2% acetyl chloride and methanol solution and kept in an oven for six hours at 45 °C. For the analysis of the esters, 1:100 dilutions were performed in hexane and injected into a gas chromatograph coupled to a mass detector. The mean seed weight was 3.14 g for H. brasiliensis, 1.7 g for H. guianensis and 5.2 g for H. spruceana. The initial establishment of H. brasiliensis, H. guianensis and H. spruceana seedlings can be classified as hypogenous-cryptocotyledonar with absorption cotyledons. The fatty acid with the highest concentration was linoleic acid for the three species. H. brasiliensis and H. guianensis showed a similar pattern of mobilization, indicating greater energy demand in the EO phase. There was no significant mobilization of fatty acids for H. spruceana in the last stages, differing from the other species. Therefore, it is concluded that despite the similarity in terms of germination and seedling development, H. spruceana has a more discreet lipid reserve mobilization strategy than H. brasiliensis and H. guianensis. Besides that the lipid mobilization is related to final development of the seedling. KEYWORDS: rubber tree; morphology of the initial establishment, mobilization of reserves; lipid reserves.