Fabrício William Ávila

Impact of selenium supply on Se-methylselenocysteine and glucosinolate accumulation in selenium-biofortified Brassica sprouts

Brassica sprouts are widely marketed as functional foods. Here we examined the effects of Se treatment on the accumulation of anticancer compound Se-methylselenocysteine (SeMSCys) and glucosinolates in Brassica sprouts. Cultivars from the six most extensively consumed Brassica vegetables (broccoli, cauliflower, green cabbage, Chinese cabbage, kale, and Brussels sprouts) were used. We found that Se-biofortified Brassica sprouts all were able to synthesize significant amounts of SeMSCys. Analysis of glucosinolate profiles revealed that each Brassica crop accumulated different types and amounts of glucosinolates. Cauliflower sprouts had high total glucosinolate content. Broccoli sprouts contained high levels of glucoraphanin, a precursor for potent anticancer compound. Although studies have reported an inverse relationship between accumulation of Se and glucosinolates in mature Brassica plants, Se supply generally did not affect glucosinolate accumulation in Brassica sprouts. Thus, Brassica vegetable sprouts can be biofortified with Se for the accumulation of SeMSCys without negative effects on chemopreventive glucosinolate contents.

Assessment of the Anticancer Compounds Se-Methylselenocysteine and Glucosinolates in Se-Biofortified Broccoli (Brassica oleracea L. var. italica) Sprouts and Florets

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.

Interação entre silício e nitrogênio em arroz cultivado sob solução nutritiva

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.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.

Carbonate-silicate ratio for soil correction and influence on nutrition, biomass production and quality of palisade grass

Silicates can be used as soil correctives, with the advantage of being a source of silicon, a beneficial element to the grasses. However, high concentrations of silicon in the plant would affect the digestibility of the forage. To evaluate the influence of the substitution of the calcium carbonate by calcium silicate on the nutrition, biomass production and the feed quality of the palisade grass [Urochloa brizantha (C. Hochstetter ex A. Rich.) R. Webster], three greenhouse experiments were conducted in completely randomized designs with four replications. Experimental units (pots) contained a clayey dystrophic Rhodic Haplustox, a sandy clay loam dystrophic Typic Haplustox and a sandy loam dystrophic Typic Haplustox. Each soil received substitution proportions (0, 25, 50, 75 and 100 %) of the carbonate by calcium silicate. The increase in the proportion of calcium silicate elevated the concentrations and accumulations of Si, Ca, Mg, and B, reduced Zn and did not alter P in the shoot of plants. The effects of the treatments on the other nutrients were influenced by the soil type. Inclusion of calcium silicate also increased the relative nutritional value and the digestibility and ingestion of the forage, while the concentration and accumulation of crude protein and the neutral detergent and acid detergent fibers decreased. Biomass production and feed quality of the palisade grass were generally higher with the 50 % calcium silicate treatment.

Selenato e selenito na produção, nutrição mineral e biofortificação com selênio em cultivares de alface¹

O selenio (Se) e um importante elemento ligado a processos fisiologicos na planta, microrganismos, animais e seres humanos. No entanto, para as plantas, seu modo de acao e sua essencialidade sao ainda motivos de controversia. No Brasil, e relevante a falta de informacoes sobre o Se nas culturas agricolas, havendo ainda indicativo de baixa ingestao desse elemento pela populacao. Assim, este estudo objetivou avaliar a influencia da aplicacao de selenato e selenito na biofortificacao com Se e o efeito dessas formas de Se nos teores de macro e micronutrientes em cultivares de alface. Utilizou-se o delineamento experimental inteiramente casualizado, em esquema fatorial 5 x 3 x 2, sendo cinco cultivares de alface (Maravilha de Verao, Rafaela, Great Lakes, Veneranda e Vera), tres concentracoes de Se (0, 10 e 20 μmol L-1) e duas formas de Se (selenato e selenito), com quatro repeticoes. Os resultados encontrados mostram que, para o cultivo de alface em solucao nutritiva, o selenato foi mais indicado para a biofortificacao com Se, enquanto o selenito mostrou ser mais toxico. A aplicacao do selenato resultou em aumento no teor de S na parte aerea, enquanto o selenito reduziu o teor de P, e ambas as formas de Se diminuiram os teores de micronutrientes. Entre as cultivares de alface, nao se observou variacao genotipica para o teor de Se, e pequena variacao foi verificada para producao de materia seca da parte aerea e teores de S, Mg, Mn e Fe.

Interação fosfito e fosfato no crescimento e na nutrição fosfatada do feijoeiro em solução nutritiva

The use of phosphite as a fungicide or supplementary source of phosphorus (P) has been intensified in recent years, however, little is known about its effects on important crops such as common bean. This work aimed to evaluate the effect of phosphite on growth and phosphate nutrition of bean plants. Two experiments in an completely randomized design were conducted in nutrient solution in a green house, from January to March 2008. In the first experiment, the treatments consisted of a 5 x 2 factorial design, with five P concentrations in the nutrient solution (0.5; 10; 20; 30 and 60 mg L-1) and two P forms: phosphite (Phi) and phosphate (Pi), with four replications. In the second experiment, the treatments consisted of five proportions of Pi: Phi in nutrient solution (100:0, 25:75, 50:50, 75:25 e 100:0), with five replications. The results showed that the shoot and root dry matter of plants grown with phosphite as the only form of P or with high proportions of Phi in relation to Pi, was drastically reduced, resulting in low P accumulation in these tissues. In conclusion, phosphate cannot be replaced by phosphite in phosphate nutrition of common bean, and has no effect on common bean under adequate phosphate supply. At no or low phosphate supply, severe phosphite toxicity symptoms were observed in the common bean plants, which are very sensitive to this anion.

Selenium behavior in the soil environment and its implication for human health

O selenio (Se) e 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 funcoes, papel relevante no sistema antioxidante dos mamiferos. Niveis inadequados de Se no corpo humano tem sido uma preocupacao bem conhecida em muitas regioes do mundo. Esse problema de desnutricao com Se ocorre frequentemente devido a dietas pobres nesse elemento, o que provavelmente tem relacao com a baixa disponibilidade de Se nos solos onde as culturas agricolas estao sendo cultivadas. Atualmente, sabe-se que, alem da quantidade de Se contida nos alimentos, sua forma (e.g., inorgânica ou orgânica) e importante para a nutricao humana. Apesar da deficiencia de Se ser um problema em alguns locais, algumas regioes do mundo apresentam niveis altos de Se nos solos, causando varias desordens e doencas nas pessoas que moram nestas areas consideradas seleniferas. Sendo um elemento essencial, o Se deve ser suprido em quantidades adequadas para evitar efeitos prejudiciais. Assim, levando-se em consideracao a importância dos solos como um meio para garantir o suprimento adequado de Se para a populacao, esta revisao tem abordado o comportamento do Se no ambiente do solo (e.g., formas de Se e reacoes de adsorcao e dessorcao) e sua relevância para a saude humana. Como mensagem final, a compreensao do comportamento de Se em solos visando prever sua disponibilidade para as culturas agricolas em diferentes sistemas sera uma abordagem significativa em estudos futuros para estabelecer formas e doses seguras de Se para serem adicionadas em fertilizantes. A biofortificacao agronomica, aliada a biofortificacao genetica, de culturas basicas com Se tem sido sugerida como importante ferramenta para melhorar a ingestao de Se pela populacao que vive em locais onde os solos sao pobres em Se.

Effect of potassium sources on the antioxidant activity of eggplant

Potassium participates in the essential processes in plant physiology, however, the effects of K sources on plant metabolism have been little studied. Also, in certain cases, K sources and concentrations may cause undesirable effects, e.g., soil salinization. The objective was to evaluate the effect of K sources and levels on the enzyme activity of the antioxidant system and protein content in eggplant (Solanum melongena L.) leaves and to determine the most suitable K sources for these physiological characteristics. The experiment was conducted in randomized blocks, in a 2 × 4 factorial design, consisting of two K sources (KCl and K2SO4) and rates (250, 500, 750, and 1000 kg ha-1 K2O), with four replications. The following variables were evaluated: plant height, number of leaves per plant, superoxide dismutase (SOD), catalase (CAT), and leaf protein content. There was an increase in CAT activity with increasing K levels until 30 days after transplanting (DAT), when K2SO4 was applied and until 60 DAT, when KCl was used; after this period, the enzyme activity decreased under both sources. The activity of SOD increased in the presence of KCl, but was reduced with the application of K2SO4. For both K sources, increasing rates reduced the protein content and number of leaves per plant, and this reduction was greater under KCl application. Thus it was concluded that KCl tends more strongly to salinize the soil than K2SO4. Both for KCl and for K2SO4, the increasing rates adversely affected the activities of CAT and SOD and the levels of leaf protein in eggplant. The potential of KCl to reduce the enzyme activity of SOD and CAT, leaf protein content and plant growth of eggplant was stronger than that of K2SO4.

Effects of selenium supplementation on glucosinolate biosynthesis in broccoli

Selenium (Se)-enriched broccoli has health-beneficial selenium-containing compounds, but it may contain reduced amounts of chemopreventive glucosinolates. To investigate the basis by which Se treatment influences glucosinolate levels, we treated two broccoli cultivars with 25 μM Na2SeO4. We found that Se supplementation suppressed the accumulation of total glucosinolates, particularly glucoraphanin, the direct precursor of a potent anticancer compound, in broccoli florets and leaves. We showed that the suppression was not associated with plant sulfur nutrition. The levels of the glucosinolate precursors methionine and phenylalanine as well as the expression of genes involved in glucosinolate biosynthesis were greatly decreased following Se supplementation. Comparative proteomic analysis identified proteins in multiple metabolic and cellular processes that were greatly affected and detected an enzyme affecting methionine biosynthesis that was reduced in the Se-biofortified broccoli. These results indicate that Se-conferred glucosinolate reduction is associated with negative effects on precursor amino acid biosynthesis and glucosinolate-biosynthetic-gene expression and provide information for a better understanding of glucosinolate accumulation in response to Se supplementation in broccoli.

Phosphite and phosphate in the accumulation and translocation of nutrients in common bean1

et al. 2006, Moor et al. 2009, Gómez-Merino & Trejo-Téllez 2015). Many beneficial effects of phosphites on crops have been reported in some studies. Tambascio et al. (2014) observed that phosphite provided an increase in the emergence of tubers, leaf area and mycorrhizal colonization in potatoes. Estrada-Ortiz et al. (2013) reported that the use of phosphite in the nutrient solution increased the concentration of free amino