Andressa Vasconcelos Flores

Alterations in seed reserves of Dalbergia nigra ((Vell.) Fr All. ex Benth.) during hydration

Seed imbibitions is the first stage of the germination process and is characterized by the hydration of tissues and cells and the activation and/or induction of the enzymes responsible for mobilizing reserves for respiration and the construction of new cell structures. The objective of this study was to investigate the alterations in reserve substances during slow hydration of Bahia Rosewood (Dalbergia nigra) seeds in water. Seeds from two different lots (Lot I and II) were placed in saturated desiccators (95-99% RH) to hydrate at 15 and 25 °C until water contents of 10, 15, 20 and 25% were reached. At each level of hydration, changes in lipid reserves, soluble carbohydrates, starch and soluble proteins were evaluated. The mobilization of reserves was similarly assessed in both lots, with no differences being observed between the two hydration temperatures. Lipid contents showed little variation during hydration, while the contents of soluble carbohydrates and starch decreased after the 15% water content level. Soluble proteins showed a gradual tendency to decrease between the control (dry seeds) up to 25% water content.

Alterações fisiológicas e bioquímicas em sementes de Pterogyne nitens tull. Durante o envelhecimento artificial

The accelerated aging test is usually used to evaluate seeds vigor and quality. This study aimed to investigate and establish relations among deterioration, physiological changes, and catalase enzyme activity, during the artificial aging process of Pterogyne nitens seeds. So, P. nitens seeds with and without dormancy overcoming, with the application of concentrated sulfuric acid (95-99%), for 10 minutes, were exposed to the accelerated aging test, for 0, 24, 48, and 72 hours, determining the germination percentage, lipids peroxidation, and catalase enzyme activity. The artificial aging process significantly affected the viability and vigor seeds, after a previous dormancy overcoming, with a decrease in germination and catalase enzyme activity and an increase in lipids peroxidation, during the aging process. For seeds that did not overcome dormancy, no relation among artificial aging, physiological changes, and enzyme activity was observed, so that dormancy acts as a protective mechanism for seeds oxidative stress.

Germinação de sementes de Melanoxylon brauna schott em diferentes temperaturas

The objective of this study was to investigate the effect of temperature on the germination of Melanoxylonbrauna seeds and identify cardinal temperatures for germination, as well as to evaluate the efficiency of the electrical conductivity test to determine the cardinal temperatures. Therefore, three testswere performed. In the first test, the determination of imbibition curves was performed at each temperature (5, 10, 15, 20, 25, 30, 35, 40 and 45oC), the seeds were weighed every two hours for a period of 12 hours and after every 12 hours until the root protrusion of 50% of the seeds, or 120 hours when there was no germination. In the second test, to identify the cardinal temperatures, seeds were kept under each temperature for a period of 10 days in DBO under constant light. In the third test, an electrical conductivity test was performed with the seeds incubated for 24, 48 and 72 hours of imbibition in each of the temperatures, and then were placed inerlenmeyer flasks with 75 mL of deionized water at 25oC for 24 hours for subsequent reading of the electrical conductivity. It is more judicious to recommend temperature ranges for germination than punctual temperatures. The cardinal temperatures (theoretical) for the characteristic germination rates are: 12.3oC - minimum - 30.0oC optimal (theoretical) and 42.7oC maximun. The temperature ranges considering all the variables investigated were: 12.1 to 12.6oC (minimum); 30.0-35.8oC (optimum) and 42.4-43.0oC (maximum). The specie has a wide range of germination with respect to temperature, and germination was observed in the temperature range from 12.0 to 42.0oC. The electrical conductivity test was efficient to evaluate the effect of temperature onseeds and according to this test the optimal temperature is 27.0oC.

Atividade enzimática durante a germinação de sementes de Melanoxylon brauna schott sob diferentes temperaturas

Objetivou-se, com este trabalho, investigar o efeito da temperatura sobre o metabolismo oxidativo, por meio da atividade das enzimas superoxido dismutase (SOD), ascorbato peroxidase (APX) e catalase (CAT) no eixo embrionario e no endosperma micropilar de sementes de Melanoxylon brauna Schott, durante a germinacao. As sementes foram semeadas em rolos de papel germitest umedecidos com agua destilada e submetidas as temperaturas constantes de 15, 25, 30 e 40oC, durante 10 dias. As determinacoes das atividades das enzimas SOD, APX e CAT foram feitas nas sementes colocadas para germinar sob as mesmas condicoes descritas acima e a cada 12 horas foram retiradas amostras ate a protrusao radicular de 50% das sementes ou 168 horas para a temperatura de 15oC. Nao foram detectadas atividades das enzimas SOD, APX e CAT no endosperma micropilar nas diferentes temperaturas. No eixo embrionario, as atividades das enzimas SOD e CAT apresentaram maiores alteracoes ao longo da germinacao em 15oC e 40oC, demonstrando que temperaturas estressantes provocam danos oxidativos. A atividade da enzima APX, no eixo embrionario, nao foi afetada pela temperatura ao longo da germinacao e sua atividade foi extremamente baixa.

ALTERAÇÕES FISIOLÓGICAS E ATIVIDADE ENZIMÁTICA EM SEMENTES ARMAZENADAS DE Melanoxylon brauna Schott.

Temperature and relative humidity set the basic conditions for the preservation of recalcitrant and orthodox seeds. The seed conservation of brauna under relative humidities of 55, 75 and 93% at 20°C was performed with the aim of evaluating germination and vigor responses, relating them to the membrane permeability, enzyme activity, content and lipid peroxidation. Increasing environment water content decreases seed quality and also decreases the activity of the enzymes superoxide dismutase and catalase, and increases activity of glucose-6-phosphate dehydrogenase. The membrane permeability increases with increasing deterioration of the seeds. There is no relationship between the changes in lipids content and peroxidation and seed deterioration.

Atividades de α-galactosidase e poligalacturonase durante a hidratação de sementes de Dalbergia nigra ((Vell.) Fr. All. ex Benth.) sob diferentes temperaturas

Germination is a process that begins with seed water uptake, stimulating enzyme synthesis or activating enzymes already present. The objective of this study was to evaluate variations in monosaccharide reserves and the activities of the α-galactosidase and polygalacturonase enzymes during the hydration of two lots of Dalbergia nigra (Bahia Rosewood) seeds. Seeds from different origins constituted the two lots I and II, classified as high and low vigor, respectively. Both lots were placed in desiccators with a high relative humidity to hydrate and at 15 and 25 °C until levels of 10, 15, 20 and 25% moisture levels in seeds were reached. The seed cotyledons were analyzed for the quantity of monosaccharides and enzyme activity. The control had higher concentrations of xylose and rhamnose, which decreased during hydration until the 15% level was reached, after which concentrations increased again in both lots. Lot I, with a superior quality, showed higher glucose synthesis and degradation during seed hydration. Both enzymes were pre-existing since activity was already present in the seeds without imbibition. The polygalacturonase enzyme increased and the α-galactosidase enzyme remained relatively constant during seed hydration.

Inoculation of Pinus taeda Seedlings with Plant Growth-promoting Rhizobacteria

The aim of this study was to evaluate the effect of Azospirillum brasilense, Bacillus subtilis and Pseudomonas fluorescens on the growth of Pinus taeda seedlings. Bacterial inoculants were applied in two different forms: at sowing and 20 days after emergence. At 30, 60 and 90 days after emergence, we evaluated plant height and root-colar diameter. At 180 days after emergence, we also measured shoot and root dry weight. Data were analyzed by analysis of variance and means were ranked by Duncan’s test. The most pronounced results were observed for root and shoot biomass when plants were inoculated with Bacillus subtilis and Pseudomonas fluorescens. Bacillus subtilis increased root and shoot biomass by 67.1% and 33.1%, respectively, when comparing values with those of non-inoculated plants. On the other hand, inoculation with Pseudomonas fluorescens decreased root biomass up to 31.42%. Inoculation with Azospirillum brasilense did not promote any difference in Pinus taeda seedling growth and may not be an efficient alternative for inoculation practices. According to these results, inoculation of Pinus taeda seedlings with Bacillus subtilis has great potential to improve plant growth regarding adaptation to field conditions.

SELECTION OF SEED LOTS OF Pinus taeda L. FOR TISSUE CULTURE

The aim of this work was to identify the fungi genera associated with three Pinus taeda L. seed lots and to assess the sanitary and physiological quality of these lots for use as selection criteria for tissue culture and evaluate the in vitro establishment of explants from seminal origin in different nutritive media. It was possible to discriminate the lots on the sanitary and physiological quality, as well as to establish in vitro plants of Pinus taeda from cotyledonary nodes obtained from aseptic seed germination of a selected lot by the sanitary and physiological quality higher. The nutritive media MS, ½ MS and WPM were equally suitable for this purpose. For the sanitary analysis the fungal genera Fusarium, Penicillium and Trichoderma were those of the highest sensitivity. For the physiological evaluation were important the variables: abnormal seedlings, strong normal seedlings; length, fresh and dry weight of strong normal seedlings. The analyzes were favorable to choose lots of seeds for in vitro culture and all culture media were adequate for the establishment of this species in tissue culture.