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 & Biology. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Stomatal control of transpiration in the canopy of a clonal Eucalyptus grandis plantation

Abstract: Predawn leaf water potential, stomatal conductance and microclimatic variables were measured on 13 sampling days from November 1995 through August 1996 to determine how environmental and physiological factors affect water use at the canopy scale in a plantation of mature clonal Eucalyptus grandis Hill ex-Maiden hybrids in the State of Espirito Santo, Brazil. The simple ”big leaf” Penman-Monteith model was used to estimate canopy transpiration. During the study period the predawn leaf water potential varied from –0.4 to –1.3 MPa, with the minimum values observed in the winter months (June and August 1996), while the average estimated values for canopy conductance and canopy transpiration fell from 17.3 to 5.8 mm s–1 and from 0.54 to 0.18 mm h–1, respectively. On the basis of all measurements, the average value of the decoupling coefficient was 0.25. During continuous soil water shortage a proportional reduction was observed in predawn leaf water potential and in daily maximum values of stomatal conductance, canopy transpiration and decoupling coefficient. The results showed that water vapour exchange in this canopy is strongly dominated by the regional vapour pressure deficit and that canopy transpiration is controlled mainly by stomatal conductance. On a seasonal basis, stomatal conductance and canopy transpiration were mainly related to predawn leaf water potential and, thus, to soil moisture and rainfall. Good results were obtained with a multiplicative empirical model that uses values of photosynthetically active radiation, vapour pressure deficit and predawn leaf water potential to estimate stomatal conductance.

Análise de trilha e correlações entre caracteres em soja cultivada em duas épocas de semeadura = Path analysis and correlations among traits in soybean grown in two dates sowing

Abstract: O conhecimento das relacoes existentes entre caracteres, tais como estimados pelas correlacoes, tem sido de grande relevância no melhoramento vegetal, pois fornece informacoes uteis ao melhorista no processo de selecao Todavia, a quantificacao e a interpretacao da magnitude das correlacoes nao implicam efeitos diretos e indiretos Nesse contexto, a analise de trilha apresenta-se como uma alternativa viavel Os objetivos deste estudo foram avaliar as correlacoes fenotipicas e genotipicas entre caracteres agronomicos importantes no melhoramento genetico da soja, realizar analise de trilha, tendo como carater principal a produtividade de graos e identificar criterios de selecao indireta para produtividade de graos Foram conduzidos dois experimentos em condicoes de casa de vegetacao, semeados em fevereiro e em dezembro de 2007 Os tratamentos foram constituidos de 90 genotipos de soja incluindo linhagens e cultivares Adotou-se o delineamento de blocos casualizados com tres repeticoes Cada unidade experimental foi constituida por tres plantas cultivadas em substrato num vaso de 3dm3 Avaliaram-se os caracteres: numero de dias para o florescimento e maturidade; altura da planta no florescimento e maturidade; numero de nos na haste principal; altura da primeira vagem; numero de vagens; produtividade de graos; numero medio de graos por vagem; e o peso de 100 graos As correlacoes genotipicas tiveram, predominantemente, magnitude superior as correlacoes fenotipicas, sendo ambas de mesmo sinal nas duas epocas de semeadura A partir das correlacoes fenotipicas, genotipicas e a analise de trilha identificaram-se o carater numero de vagens por planta, independentemente da epoca de semeadura, de maior efeito favoravel sobre a produtividade de graos

Vitamin D: Link between Osteoporosis, Obesity, and Diabetes?

Abstract: Vitamin D (1,25(OH)2D3) is a steroid hormone that has a range of physiological functions in skeletal and nonskeletal tissues, and can contribute to prevent and/or treat osteoporosis, obesity, and Type 2 diabetes mellitus (T2DM). In bone metabolism, vitamin D increases the plasma levels of calcium and phosphorus, regulates osteoblast and osteoclast the activity, and combats PTH hypersecretion, promoting bone formation and preventing/treating osteoporosis. This evidence is supported by most clinical studies, especially those that have included calcium and assessed the effects of vitamin D doses (≥800 IU/day) on bone mineral density. However, annual megadoses should be avoided as they impair bone health. Recent findings suggest that low serum vitamin D is the consequence (not the cause) of obesity and the results from randomized double-blind clinical trials are still scarce and inconclusive to establish the relationship between vitamin D, obesity, and T2DM. Nevertheless, there is evidence that vitamin D inhibits fat accumulation, increases insulin synthesis and preserves pancreatic islet cells, decreases insulin resistance and reduces hunger, favoring obesity and T2DM control. To date, there is not enough scientific evidence to support the use of vitamin D as a pathway to prevent and/or treat obesity and T2DM.

Coffee growth, pest and yield responses to free-air CO2 enrichment

Abstract: Despite the importance of coffee as a globally traded commodity and increasing concerns about risks associated with climate change, there is virtually no information about the effects of rising atmospheric [CO2] on field-grown coffee trees. This study shows the results of the first 2 years of an innovative experiment. Two commercial coffee cultivars (Catuai and Obata) were grown using the first free-air CO2 enrichment (FACE) facility in Latin America (ClimapestFACE). Plants of both cultivars maintained relatively high photosynthetic rates, water-use efficiency, increased growth and yield under elevated [CO2]. Harvestable crop yields increased 14.6 % for Catuai and 12.0 % for Obata. Leaf N content was lower in Obata (5.2 %) grown under elevated [CO2] than under ambient [CO2]; N content was unresponsive to elevated [CO2] in Catuai. Under elevated [CO2] reduced incidence of leaf miners (Leucoptera coffeella) occurred on both coffee cultivars during periods of high infestation. The percentage of leaves with parasitized and predated mines increased when leaf miner infestation was high, but there was no effect of elevated [CO2] on the incidence of natural enemies. The incidence of rust (Hemileia vastatrix) and Cercospora leaf spot (Cercospora coffeicola) was low during the trial, with maximum values of 5.8 and 1 %, respectively, and there was no significant effect of [CO2] treatments on disease incidence. The fungal community associated with mycotoxins was not affected by the treatments.

Deforestation reduces rainfall and agricultural revenues in the Brazilian Amazon.

Abstract: It has been suggested that rainfall in the Amazon decreases if forest loss exceeds some threshold, but the specific value of this threshold remains uncertain. Here, we investigate the relationship between historical deforestation and rainfall at different geographical scales across the Southern Brazilian Amazon (SBA). We also assess impacts of deforestation policy scenarios on the region’s agriculture. Forest loss of up to 55–60% within 28 km grid cells enhances rainfall, but further deforestation reduces rainfall precipitously. This threshold is lower at larger scales (45–50% at 56 km and 25–30% at 112 km grid cells), while rainfall decreases linearly within 224 km grid cells. Widespread deforestation results in a hydrological and economic negative-sum game, because lower rainfall and agricultural productivity at larger scales outdo local gains. Under a weak governance scenario, SBA may lose 56% of its forests by 2050. Reducing deforestation prevents agricultural losses in SBA up to US$ 1 billion annually. Deforestation in the Amazon region has suggested to influence precipitation in a non-linear way. Here, the authors show that forest loss is associated with decreasing precipitation after a scale-dependent threshold is crossed, which can cause stress on agriculture if deforestation is expanded.