No abstract

Selenium is an important element associated with enhancement of antioxidant activity in plants, microorganisms, animals, and humans. In Brazil, the information on Se in agricultural crops is lacking, though there are indications that low levels of Se are consumed by the population. The experiment was conducted under greenhouse conditions with pots containing 3 l of nutritive solution in a completely randomized factorial design, with seven Se concentrations (0, 2, 4, 8, 16, 32, and 64 µmol/l) and two forms of Se (sodium selenate -Na 2 SeO 4 and sodium selenite -Na 2 SeO 3 ), with six replicates. The application of Se as selenate at low concentrations is more appropriate for lettuce biofortification because it favors shoot biomass growth and Se levels in the shoot biomass. Selenium in both forms had two effects on lettuce plant metabolism: at low doses it acted as an antioxidant and enhanced plant growth, whereas at higher levels it reduced yield.

Broccoli (Brassica oleracea L. var. italica) is a rich source of chemopreventive compounds. Here, we evaluated and compared the effect of selenium (Se) treatment on the accumulation of anticancer compounds Se-methylselenocysteine (SeMSCys) and glucosinolates in broccoli sprouts and florets. Total Se and SeMSCys content in sprouts increased concomitantly with increasing Se doses. Selenate was superior to selenite in inducing total Se accumulation, but selenite is equally effective as selenate in promoting SeMSCys synthesis in sprouts. Increasing sulfur doses reduced total Se and SeMSCys content in sprouts treated with selenate, but not in those with selenite. Examination of five broccoli cultivars reveals that sprouts generally have better fractional ability than florets to convert inorganic Se into SeMSCys. Distinctive glucosinolate profiles between sprouts and florets were observed, and sprouts contained approximately 6-fold more glucoraphanin than florets. In contrast to florets, glucosinolate content was not affected by Se treatment in sprouts. Thus, Se-enriched broccoli sprouts are excellent for simultaneous accumulation of chemopreventive compounds SeMSCys and glucoraphanin.

No abstract

This study aims to explain the effects of silicon on chlorophyll and to measure gas exchange and carbohydrate levels in two Lycopersicon esculentum cultivars that are exposed to drought. The experimental design used in this study was a randomised combination of five different water and silicon conditions (control, water deficit + 0.00 μmol Si, water deficit + 0.25 μmol Si, water deficit + 1.00 μmol Si, and water deficit + 1.75 μmol Si) applied to the two cultivars (Super Marmante and Santa Cruz). Parameters measured were gas exchanges, chlorophylls, and total soluble carbohydrates. Silicon at concentrations of 0.25, 1.00, and 1.75 μmol induced a gradual increase in the total chlorophyll levels. A correlation analysis revealed a linear, positive interaction between the leaf water potential and the total chlorophyll (r = 0.71; P < 0.05). This study confirmed the hypothesis that silicon has a beneficial effect with regard to chlorophyll. Under water-deficient conditions, both cultivars showed an increase in chlorophyll a when treated with silicon in addition to changes in the total chlorophyll levels. These results were supported by the change in leaf water potential. In addition, a reduction of the effects of water restriction was also observed in the transpiration rate, the stomatal conductance and in the levels of total carbohydrates.

summarY the expansion of Brazilian agriculture has led to a heavy dependence on imported fertilizers to ensure the supply of the growing food demand. this fact has contributed to a growing interest in alternative nutrient sources, such as ground silicate rocks. it is necessary, however, to know the potential of nutrient release and changes these materials can cause in soils. the purpose of this study was to characterize six silicate rocks and evaluate their effects on the chemical properties of treated soil, assessed by chemical extractants after greenhouse incubation. the experimental design consisted of completely randomized plots, in a 3 x 6 factorial scheme, with four replications. the factors were potassium levels (0-control: without silicate rock application; 200; 400; 600 kg ha -1 of k 2 o), supplied as six silicate rock types (breccia, biotite schist, ultramafic rock, phlogopite schist and two types of mining waste). the chemical, physical and mineralogical properties of the alternative rock fertilizers were characterized. treatments were applied to a dystrophic red-Yellow oxisol (ferralsol), which was incubated for 100 days, at 70 % (w/w) moisture in 3.7 kg/pots. the soil was evaluated for ph; calcium and magnesium were extracted with kCl 1 mol l -1 ; potassium, phosphorus and sodium by mehlich 1; nickel, copper and zinc with dtPa; and the saturation of the cation exchange capacity was calculated for aluminum, calcium, magnesium, potassium, and sodium, and overall base saturation. the alternative fertilizers affected soil chemical properties. ultramafic rock and Chapada mining byproduct (CmB) were the silicate rocks that most influenced (1) received for publication in June 29, 2011 and approved in april 12, 2012. (2) Professor soil science department, federal university of lavras -ufla. CP 3037, CeP 37200-000 lavras (mG), Brazil. e-mails:douglasguelfi@dcs.ufla.br; guilherm@dcs.ufla.br (3) research embrapa Cerrados, rodovia Br 020, km 18, CeP 73370-970 Planaltina (df), Brazil. e-mails: giuliano.marchi@cpac. embrapa.br; rein@cpac.embrapa.br (4) Professor faculty of agronomy and Veterinary medicine, university of Brasília, Campus universitário darcy ribeiro, asa norte, CeP 70910-970 Brasília (df), Brazil. e-mail: spehar@unb.br (5) student of the doctorate Program on

Selenium (Se) is an important element that was discovered in 1817, and since the 1960s, it has been regarded as an essential micronutrient for both animals and humans, playing among other functions a relevant role in the antioxidant system of mammals. Inadequate blood Se levels in the human body is a well-known concern in many parts of the world. This malnutrition problem is often due to Se-poor diet, probably as a result of the low Se availability in soils where crops are growing. Nowadays, it is known that not only the total content, but also the inorganic and organic forms of Se contained in foods are important for human nutrition. However, paradoxically some regions of the world present high Se levels in soils causing several functional disorders and diseases in people who live in seleniferous areas. As essential micronutrient, Se should be supplied in controlled amounts to avoid harmful effects. Therefore, taking into account the importance of the soils as a way to ensure the adequate Se supply for the population, this review has dealt with Se behavior in soil environment (e.g., Se forms and adsorption and desorption reactions) and its relevance for the human health. As a final message, the further understanding of Se behavior in soils to predict its availability for crops in different systems will be a significant approach in future studies to establish forms and safe doses of Se to be added in fertilizers. Agronomic and genetic biofortification of staple crops with Se has been suggested as an important tool to improve Se intake by population in Se-poor sites.Index terms: Essential micronutrient; Se adsorption; Se availability; biofortification; human nutrition. RESUMOO selênio (Se) é um elemento importante que foi descoberto em 1817 e reconhecido como elemento essencial para os humanos e animais desde os anos 60. Esse elemento apresenta, dentre outras funções, papel relevante no sistema antioxidante dos mamíferos. Níveis inadequados de Se no corpo humano tem sido uma preocupação bem conhecida em muitas regiões do mundo. Esse problema de desnutrição com Se ocorre frequentemente devido a dietas pobres nesse elemento, o que provavelmente tem relação com a baixa disponibilidade de Se nos solos onde as culturas agrícolas estão sendo cultivadas. Atualmente, sabe-se que, além da quantidade de Se contida nos alimentos, sua forma (e.g., inorgânica ou orgânica) é importante para a nutrição humana. Apesar da deficiência de Se ser um problema em alguns locais, algumas regiões do mundo apresentam níveis altos de Se nos solos, causando várias desordens e doenças nas pessoas que moram nestas áreas consideradas seleníferas. Sendo um elemento essencial, o Se deve ser suprido em quantidades adequadas para evitar efeitos prejudiciais. Assim, levando-se em consideração a importância dos solos como um meio para garantir o suprimento adequado de Se para a população, esta revisão tem abordado o comportamento do Se no ambiente do solo (e.g., formas de Se e reações de adsorção e dessorção) e sua relevância para a saúde hu...

Resumo -O presente estudo objetivou avaliar o efeito da interação entre silício e nitrogênio nos teores de clorofila, nitrato, amônio e nitrogênio total, na produção de biomassa e nos números de perfilhos e de panículas em arroz cultivado em solução nutritiva. Utilizou-se o delineamento inteiramente casualizado em esquema fatorial 5 x 2, sendo duas concentrações de silício (0 e 50 mg L -1 ) e cinco as de nitrogênio (20; 50; 100; 200 e 400 mg L -1 ), com três repetições. No estádio de formação do colar da folha bandeira foram realizadas a leitura SPAD e as determinações dos teores de clorofila a e b, nitrogênio nítrico, amoniacal e total. No estádio de maturidade completa da panícula, foram avaliados os números de perfilhos e de panículas e determinaram-se os pesos de matéria seca de raiz e parte aérea e o acúmulo de silício na planta. Os resultados mostraram que o fornecimento de silício não alterou o perfilhamento, a produção de matéria seca e os teores de nitrogênio total. O silício elevou os valores SPAD, os teores de clorofila a e b, os teores de nitrato nas raízes e o número de panículas, especialmente em doses elevadas de nitrogênio.Palavras-chave -Oryza sativa. Perfilhamento. Clorofila. SPAD. Abstract -The present study aimed to evaluate the interaction effect between silicon and nitrogen in the content of chlorophyll, nitrate, ammonium and total nitrogen, dry matter production, number of tillers and number of panicles rice-plant cultivated in nutritional solution. A factorial design 5 x 2 trial installed in a completely randomized design was used being two silicon (0 and 50mg L -1 ) and five nitrogen (20; 50; l00; 200 and 400 mg L -1 ) concentrations. In the stadium of the flag leaf collar formation SPDA reading and the a and b chlorophyll contents, ammoniacal and total nitrogen determinations in plants were detemined. During the panicle complete maturity stadium, the number of tillers and panicles were evaluated and the aerial part and root dry matter contents and silicon accumulation were determined. The outcomes show that the silicon supply did not change the tillering, the dry matter production and total nitrogen contents. The silicon increased the SPAD values, the a and b chlorophyll and the root nitrate contents, and the number of panicles, especially at high nitrogen levels.