Fisiologia, bioquímica e anatomia de sementes de Melanoxylon brauna Schott. (Fabaceae) germinadas em diferentes temperaturas

• Autor(a) principal: Ataíde, Glauciana da Mata
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/607
• topic: Germinação; Vitalidade; Sementes; Germination; Vitality; Seeds; CNPQ::CIENCIAS AGRARIAS::RECURSOS FLORESTAIS E ENGENHARIA FLORESTAL::SILVICULTURA

Seeds germinate when environmental conditions are favorable for growth and they do not have any dormancy. Among the factors affecting the germination process, the temperature takes a prominent position, in that it determines the capacity and rate of seed germination, affecting the speed of absorbing water and biochemical reactions that govern the development of germination. Considering that temperature is essential for the development of germination, the aim of this work was to study physiological, biochemical and anatomical changes associated with germination of Melanoxylon brauna seeds at different temperatures. Therefore, experiments were conducted in the Laboratories of Analysis of Forest Seeds and Plant Anatomy, at Federal University of Viçosa - UFV. Were used in this study seeds of M. brauna collected in two different years, 2010 and 2012, which constituted the lots I and II. Initially, in Chapter 1, a study was done to evaluate the influence of the amount of seeds, water volume and time of soaking in electrical conductivity for seeds of the species, for the establishment of specific methodology for assessing the vigor through this test. Seed samples of two lots were tested in combinations with 25, 50 and 75 seeds in volumes of 25, 50 and 75 mL of distilled water, at times 24, 48 and 72 hours of imbibition. To Chapters 2, 3 and 4 were used only seed lot II, collected in 2012, which were put to soak at the constant temperatures of 10, 25, 30 and 40 o C. In the second chapter, were evaluated the percentage, speed and time of germination of seeds at each temperature, and the ability to rollback the seeds when transferred to 25 ° C after exposure to temperatures of 10 and 40 o C. Were also evaluated biometric changes in seeds at constant temperatures of 10, 25, 30 and 40 ° C by means of the analysis of water content, fresh weight, length, width and thickness of the seed, and length and fresh weight of embryonic axes. In the third chapter were studied the mobilization of reserve substances in cotyledons of seeds of M. brauna during germination at different temperatures, and quantified the concentrations of lipids, soluble sugars, starch and soluble proteins, and the activities of the enzymes α-amylase, β-amylase and glucose-6-phosphate dehydrogenase. The fourth chapter studied the structural and histochemical changes in cotyledons and embryonic axes of M. brauna seeds during germination at temperatures 10, 25, 30 and 40 ° C. Results indicated that the electrical conductivity test should be conduct at time of 48 hours of soaking, with 50 seeds and 50 mL of water. For germination, the seeds of M. brauna had higher average at temperatures of 25 and 30 o C, with values of 93 and 98%, respectively, while the temperatures of 10 and 40 o C germination was 5%. The soaking of seeds at 10 and 40 ° C with subsequent return to 25 ° C resulted in increases in germination at all times studied. Changes in reserves of soluble carbohydrates showed the strongest evidence of decline during the period of germination of Melanoxylon brauna, especially at 25 and 30 ° C, where the activity of the enzymes α-amylase, β- amylase and glucose-6 -phosphate dehydrogenase increases with seed imbibition, generating substrate for the respiration and formation of carbon structures for growth. The proteins decrease significantly in the early period after germination, at a temperature of 30 ° C. At temperatures 10 and 40 ° C, above and below the optimum range for germination of the species, the activity of the enzymes α-amylase, β-amylase and glucose-6-phosphate dehydrogenase is reduced, impairing proper development of the germination process. Anatomically, it was possible to visualize the lipid reserves remained constant during the study period, being responsible for the maintenance of seedlings after the start of growth. As a result, were observed the formation of starch granules in the seeds after radicle protrusion at 30 ° C, results consistent with the information collected for enzymatic activity and seed germination at this temperature. The structural analysis confirms the presence of vacuolated cells, elongated, juxtaposed with intense cellular activity after onset of imbibition.