Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Dry matter. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Produção de serapilheira em clareiras de uma floresta estacional semidecidual no município de Campinas, SP

Abstract: Litter production was studied in 10 natural gaps of Santa Genebra Municipal Reserve (22°49'45"S and 47°06'33"W) in Campinas, Sao Paulo state. Thirty wooden litter traps of 0.5 x 0.5 m with nylon screen bottoms and 1.0 mm2 mesh were used, placed 10 cm above the surface of the soil. Collections took place on a monthly basis, from January to December of 1997. In laboratory, the material deposited in the traps was separated in the fractions of leaves, branches (up to 2.0 cm of diameter), flowers and fruits, dried in stove to 70°C and weighed in analytic scale. The annual litter production for the gaps as a whole was estimated in 5968 kg.ha­1, the fraction leaves accorenting for 75.87% of the total dry weight, followed by branches, fruits and flowers with 19.27%, 3.17% and 1.69%, respectively. Litter production was uniform throughout the year, thus showing a seasonal pattern with the largest values at the end of the dry season, reaching a maximum value in September. Among gaps, litter production was significantly and positively correlated with the dominance of pioneer species.

Yacon Flour and Bifidobacterium longum Modulate Bone Health in Rats

Abstract: Yacon flour has been considered a food with prebiotic potential because of the high levels of fructooligosaccharides, which allows for its use in formulating synbiotic foods. The purpose of this study was to evaluate the effect of yacon flour and probiotic (Bifidobacterium longum) on the modulation of variables related to bone health. Thirty-two Wistar rats were divided into 4 groups: control, yacon flour, diet+B. longum, and yacon flour+B. longum. After euthanasia, the bones were removed for analysis of biomechanical properties (thickness, length, and strength of fracture) and mineral content (Ca, Mg, and P); the cecum was removed for analysis of the microbiota and short-chain fatty acids. Tibia Ca, P, and Mg content was significantly (P<.05) higher in groups fed diet+B. longum, yacon flour+B. longum than in the control group. An increase in fracture strength was observed in the yacon flour (8.1%), diet+B. longum (8.6%), and yacon flour+B. longum (14.6%) in comparison to the control group. Total...

Glutathione S-transferase detoxification as a potential pyrethroid resistance mechanism in the maize weevil, Sitophilus zeamais

Abstract: Insecticide resistance patterns among 16 Brazilian populations of the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), were recognized by surveying resistance to three organophosphates (chlorpyrifos-methyl, malathion, and pirimiphos-methyl) and three pyrethroids (cypermethrin, deltamethrin, and permethrin). Two population clusters were obtained: one with three populations (Braganca Paulista, Cristalina, and Nova Andradina) showing low frequency of cypermethrin resistance (13-36%) and negligible frequency of deltamethrin resistance (2-9%); and another with six populations (Campos dos Goytacazes, Ivinhema, Patos de Minas, Penapolis, Uberlândia, and Venda Nova) showing low to negligible levels of pyrethroid resistance (0-23%). The remaining seven populations, including a susceptible, and a DDT- and pyrethroid-resistant reference populations (Sete Lagoas and Jacarezinho, respectively), were significantly different from each other and from the two recognized clusters. In contrast with pyrethroid resistance, organophosphate resistance was negligible except for chlorpyrifos-methyl in two populations (Fatima do Sul and Penapolis). There was no correlation between geographic distance and the Mahalanobis distance estimated from the resistance pattern ordination of the populations by canonical variate analysis, suggesting local selection and/or broad dispersal of resistant populations by grain trade. The results of biochemical in vitro studies measuring the activity of detoxification enzymes (esterases and glutathion S-transferases) in conjunction with canonical correlation analysis suggest a major involvement of enhanced conjugation by glutathione S-transferases (> 2-fold increase) in pyrethroid resistance and, in the case of cypermethrin resistance, enhanced phosphotriesterase activity.

Silicon nutrition alleviates the negative impacts of arsenic on the photosynthetic apparatus of rice leaves: an analysis of the key limitations of photosynthesis.

Abstract: Silicon (Si) plays important roles in alleviating various abiotic stresses. In rice (Oryza sativa), arsenic (As) is believed to share the Si transport pathway for entry into roots, and Si has been demonstrated to decrease As concentrations. However, the physiological mechanisms through which Si might alleviate As toxicity in plants remain poorly elucidated. We combined detailed gas exchange measurements with chlorophyll fluorescence analysis to examine the effects of Si nutrition on photosynthetic performance in rice plants [a wild-type (WT) cultivar and its lsi1 mutant defective in Si uptake] challenged with As (arsenite). As treatment impaired carbon fixation (particularly in the WT genotype) that was unrelated to photochemical or biochemical limitations but, rather, was largely associated with decreased leaf conductance at the stomata and mesophyll levels. Indeed, regardless of the genotypes, in the plants challenged with As, photosynthetic rates correlated strongly with both stomatal (r(2) = 0.90) and mesophyll (r(2) = 0.95) conductances, and these conductances were, in turn, linearly correlated with each other. The As-related impairments to carbon fixation could be considerably reverted by Si in a time- and genotype-dependent manner. In conclusion, we identified Si nutrition as an important target in an attempt to not only decrease As concentrations but also to ameliorate the photosynthetic performance of rice plants challenged with As.