Ação antioxidante da água catódica: estudos preliminares em sementes de café

Coffee seeds have limitations regarding to its conservation because of their sensitivity to desiccation and storage behavior. The establishment of a methodology for seed storage is difficult due to its deterioration. Deterioration can enhance the production of reactive oxygen species and cause lethal oxidative damage to plant tissues. The damage caused by harmful levels of free radicals can be softened by the action of endogenous or exogenous antioxidants. Recent research shows new antioxidative protection technologies, being cathodic protection a promising technique with relevant results in other recalcitrant species and even in other living organisms. Thus, the aim of this work was to verify the antioxidant effect of cathodic water in Coffea arabica L. seeds with the purpose of investigating a new technology to improve seed quality. The study was conducted at the Central Seed Laboratory, Department of Agriculture, at the Federal University of Lavras. Coffea arabica L. seeds were used. The study was conducted in two stages, in the first a preliminary analysis of the use of cathodic water was carried out in batches with different levels of quality. In the second it was evaluated the effect of light and of the imbibition period of the seeds in cathodic water. The seeds were immersed in distilled water and in cathodic water for eight distinct soaking periods, in absence and presence of light and then evaluated by physiological tests. It can be concluded that cathodic water can positively influence the physiological performance of the coffee seeds with poor quality, especially when embedded during periods between 4.5 to 7.5 hours in the absence of light.

Biofortificação com zinco, selênio e ferro, e biodisponibilidade de ferro em cultivares de feijoeiro-comum

The common bean (Phaseolus vulgaris L.), a staple food in nutritional diet of Brazilians and populations in developing countries, is a nutritionally rich legume with potential for biofortification. Approximately one third of the world population suffers from nutritional deficiencies, being necessary to increase the nutrient content in vegetables, especially iron (Fe), selenium (Se) and zinc (Zn), which are important micronutrients for plants and human health. In this context, three studies were carried out aiming to evaluate the potential of common bean cultivars to biofortification with Fe, Se and Zn, and verify the interaction between these minerals and iron bioavailability, in order to contribute to increased nutritional quality of grains, reducing the micronutrients deficiency and improving human health. In the first study, experiments were conducted in a greenhouse, with ten common bean cultivars in nutrient solution under different treatments with Fe, Se and Zn. The plant growth and the mineral content of the beans were evaluated in addition to verify the influence of polyphenol and phytate levels on Fe bioavailability in grains fortified with Zn and Se. The evaluated beans cultivars have proved promising for simultaneous biofortification with these nutrients without greatly affecting Fe bioavailability. In the second study, the aim was evaluate the interaction between Fe, Se and Zn in cultivars consumed in Brazil or in USA. Gene expression and root microscopy analysis were performed in order to understand the positive effect of Zn supply on the Fe uptake by roots. The expression of genes related to the transport and uptake of Fe and Zn did not clearly explain the influence of Zn in Fe nutrition. The roots microscopy and the evaluation of nutrient solutions used showed that, in the presence of Zn, there was Fe accumulation in epidermis of the roots and not in the vascular system, prone to be precipitated when it goes through the root membrane. In the latest study, a field experiment was conducted to evaluate the effect of Zn fertilization via soil and foliar, in the content and accumulation of Fe and Zn in grains and in the yield of common bean cultivars, in addition to verify the amount of these micronutrients supplied by biofortified beans. The fertilization with Zn did not affect the yield, but provided high levels of this nutrient in grains of the cultivars analyzed, representing 27% of the recommended daily intake of Zn. The higher Fe content in beans, obtained when there was no application of foliar Zn, supplies 56% of the daily requirement of Fe.

Metodologias para a avaliação do potencial fisiológico de sementes de tabaco

Despite tobacco being a culture propagated by seeds, there is little information concerning tests that allow the distinction of similar germination lots in different levels of vigor. The diversity of cultivars available in the market, and a few peculiarities of the species, such as uneven maturation of the flowers, fruits and seeds, small size and seed dormancy, are considered obstacles for obtaining lots of tobacco of high physiological potential. Thus, this research was developed with the objective of adapting feasibility and vigor tests for evaluating the physiological potential of tobacco seed lots. We used nine lots of tobacco seeds of cultivar CSC 447 and nine lots of seeds of cultivar BAT 2101, belonging to variety groups Virginia and Burley, respectively. Initially, germination test was conducted to characterize the profile of the lots. For determining the feasibility and vigor of the tobacco seeds, germination tests were conducted in distinct temperatures, controlled emergence conditions, electric conductivity, artificial aging and in tetrazolium. For determining the isoenzymatic marker for seed quality, analyses were conducted with enzymes catalase, esterase, malate dehydrogenase and alcohol dehydrogenase. In conclusion, the emergence tests at 25oC and artificial aging at 41oC for 72 hours, are efficient in discriminating the lots of tobacco seeds in different levels of vigor. The electric conductivity and germination tests in different temperatures have distinct responses in relation to the genotype of the tobacco seeds. The tetrazolium test using the methodology with pre-conditioning in 3.5% sodium hypochlorite solution and subsequent emersion in 1.0% tetrazolium solution for 18 hours is efficient for the quick evaluation of the feasibility of tobacco seeds. The analysis of the profiles of enzymes catalase, esterase, malate dehydrogenase and alcohol dehydrogenase is efficient as markers for tobacco seed quality.