The relationship between leaf nitrogen, nitrogen metabolites and herbivory in two species of Nyctaginaceae from the Brazilian Cerrado

Guapira graciliflora and Neea theifera are taxonomically related species of the tribe Pisoneae. Both species are found in the same environment, the Brazilian Cerrado, and therefore, are subjected to similar selective pressures. These species occur in oligotrophic environments, yet contain high concentrations of nitrogen in their leaves. The present study was carried out to investigate the ecological role of nitrogen in herbivory on these species. The differences in the N content, compositions of secondary N-metabolites, mechanical resistance, and water content between their leaves indicate that these species have different adaptations as defense mechanisms. In both species, their high nitrogen content seems to promote herbivory. The presence of secondary nitrogen metabolites does not prevent the species from suffering intense damage by herbivores on their early leaves. The herbivory rates observed were lower for mature leaves of both species than for young leaves. In G. graciliflora, nutritional content and leaf hardness are the most important variables correlated with reduction of herbivory rates, whereas in N. theifera, N compounds are also correlated with herbivory rates. Despite the differences in the strategies of these two species, they exhibit a similar efficiency of protection against natural enemies because their total herbivory rates are similar. The difference in their N defense allocation may imply benefits for survival under Cerrado conditions. We briefly discuss the oligotrophic habitat conditions of the studied plants and possible advantages of their strategies of N accumulation and metabolic uses. (C) 2011 Elsevier B.V. All rights reserved.

Growth and nitrogen fixation in soybean treated with doses of composted sewage sludge

The use of sewage sludge is a highly promising practice for the development of sustainable agricultural systems. The objective of this study was to evaluate doses of sewage sludge composted with and without Rhizobium inoculation in leaf N content, nodule number, nodule dry weight and plant during flowering. The experiment was conducted in the greenhouse of the Department of Soil Science and Natural Resources College of Agricultural Sciences of Botucatu, using as substrate used in vessels of 30 liters a Red Yelow Latosol sandy texture with experimental design adopted was randomized blocks constituted for 10 treatments and five doses of composted sewage sludge (0, 10, 20, 30, 40 t ha(-1)) with or without inoculation Bradyrhizobium japonic with three replications. There was an increase in the number and dry weight of nodules and shoot dry mass of soybeans due to the increase of the dose of sludge up to a dose of 20 t ha(-1) and after this dose there was a decrease of these parameters. At a dose of 10 t ha(-1) sludge compost inoculated seeds showed higher for foliar concentrations of N and number of nodules compared with uninoculated seeds. At a dose of 30 t ha(-1) inoculated seeds were higher compared to uninoculated in all parameters.

Arthrospira platensis biomass with high protein content cultivated in continuous process using urea as nitrogen source

Aims: Arthrospira platensis has been studied for single-cell protein production because of its biomass composition and its ability of growing in alternative media. This work evaluated the effects of different dilution rates (D) and urea concentrations (N0) on A.similar to platensis continuous culture, in terms of growth, kinetic parameters, biomass composition and nitrogen removal. Methods and results: Arthrospira platensis was continuously cultivated in a glass-made vertical column photobioreactor agitated with Rushton turbines. There were used different dilution rates (0.040.44 day-1) and urea concentrations (0.5 and 5 mmol l-1). With N0 = 5 mmol l-1, the maximum steady-state biomass concentration was1415 mg l-1, achieved with D = 0.04 day-1, but the highest protein content (71.9%) was obtained by applying D = 0.12 day-1, attaining a protein productivity of 106.41 mg l-1 day-1. Nitrogen removal reached 99% on steady-state conditions. Conclusions: The best results were achieved by applying N0 = 5 mmol l-1; however, urea led to inhibitory conditions at D = 0.16 day-1, inducing the system wash-out. The agitation afforded satisfactory mixture and did not harm the trichomes structure. Significance and Impact of the Study: These results can enhance the basis for the continuous removal of nitrogenous wastewater pollutants using cyanobacteria, with an easily assembled photobioreactor.

Spatial variability of leaf nutrient contents in a drip irrigated citrus orchard

This study aimed to evaluate the spatial variability of leaf content of macro and micronutrients. The citrus plants orchard with 5 years of age, planted at regular intervals of 8 x 7 m, was managed under drip irrigation. Leaf samples were collected from each plant to be analyzed in the laboratory. Data were analyzed using the software R, version 2.5.1 Copyright (C) 2007, along with geostatistics package GeoR. All contents of macro and micronutrients studied were adjusted to normal distribution and showed spatial dependence.The best-fit models, based on the likelihood, for the macro and micronutrients were the spherical and matern. It is suggest for the macronutrients nitrogen, phosphorus, potassium, calcium, magnesium and sulfur the minimum distances between samples of 37; 58; 29; 63; 46 and 15 m respectively, while for the micronutrients boron, copper, iron, manganese and zinc, the distances suggests are 29; 9; 113; 35 and 14 m, respectively.

Kinetic and thermodynamic investigation of Arthrospira (Spirulina) platensis fed-batch cultivation in a tubular photobioreactor using urea as nitrogen source

BACKGROUND: Fed-batch culture allows the cultivation of Arthrospira platensis using urea as nitrogen source. Tubular photobioreactors substantially increase cell growth, but the successful use of this cheap nitrogen source requires a knowledge of the kinetic and thermodynamic parameters of the process. This work aims at identifying the effect of two independent variables, temperature (T) and urea daily molar flow-rate (U), on cell growth, biomass composition and thermodynamic parameters involved in this photosynthetic cultivation. RESULTS: The optimal values obtained were T = 32 degrees C and U = 1.16 mmol L-1 d-1, under which the maximum cell concentration was 4186 +/- 39 mg L-1, cell productivity 541 +/- 5 mg L-1 d-1 and yield of biomass on nitrogen 14.3 +/- 0.1 mg mg-1. Applying an Arrhenius-type approach, the thermodynamic parameters of growth (?H* = 98.2 kJ mol-1; ?S* = - 0.020 kJ mol-1 K-1; ?G* = 104.1 kJ mol-1) and its thermal inactivation (Delta H-D(0) =168.9 kJ mol-1; Delta S-D(0) = 0.459 kJ mol-1 K-1; Delta G(D)(0) =31.98 kJ mol-1) were estimated. CONCLUSIONS: To maximize cell growth T and U were simultaneously optimized. Biomass lipid content was not influenced by the experimental conditions, while protein content was dependent on both independent variables. Using urea as nitrogen source prevented the inhibitory effect already observed with ammonium salts. Copyright (c) 2012 Society of Chemical Industry

PRODUCTION AND CHEMICAL COMPOSITION OF VEGETABLES HARDWOOD IN HYDROPONICS

The hydroponic cultivation of vegetables has increased markedly in recent years, however, little is known about its chemical composition, which is of extreme importance in view of changing food habits of a considerable fraction of the population seeking food quality. For this reason, cultivation of watercress, chicory, rocket and lettuce American (Lucy Brown) and smooth (cv. Regina) were grown in hydroponics, NFT system, aiming to evaluate the yield, nitrate content and chemical composition. The experiment was conducted in a greenhouse at the Universidade Federal de Santa Catarina, Florianopolis city in the Santa Catarina State (Brazil), from may to july 2004 under a completely randomized design with four replications. The spacing used was 25 x 25 cm for the crops of watercress, chicory and lettuce (cv. Lucy Brown and cv. Regina) and 5 x 5 cm to the rocket. The traits were: number of leaves, nitrate content and chemical composition of vegetables. The lettuce cv. Regina and chicory had higher number of leaves per plant. The watercress had lower water content and higher dry mass of shoots. The largest increase in fresh weight was obtained in chicory, lettuce, cv. Regina. Higher levels of lipids, protein, ash, carbohydrates, calories, fiber and nitrate were obtained from the watercress. The rocket had lower values for the variables fresh and dries the whole plant, shoot and root and leaf number per plant. All cultures showed good visual appearance, low calorie and nitrate levels suitable for human consumption.

PHYSIOLOGICAL CHANGES IN SEEDS AND ANTIOXIDANT METABOLISM OF LETTUCE SEEDLING EXPOSED TO THE ACTION OF Zantedeschia aethiopica Spreng. LEAF EXTRACT

This work aimed to evaluate the influence of different concentrations of Zantedeschia aethiopica Spreng. extract on the physiological performance of the seed and on the response of the antioxidant metabolism of lettuce seedlings. The treatments consisted of leaves extracts from Z. aethiopica at concentrations of 0, 6, 12, 25 and 50%. Germination, first germination count, germination speed and index, length of shoot and radicle, seedling total dry mass, chlorophyll content, activity of superoxide dismutase, catalase and ascorbarte peroxidase enzymes, lipid peroxidation, hydrogen peroxide quantification and seedling emergence, length of organs, and total dry mass of seedlings were evaluated. The percentage of germination, the length of the shoot and radicle of seedlings and the total dry mass of seedlings grown in the greenhouse were reduced as the concentration of the extract increased. There were increases of electrical conductivity, of superoxide dismutase, catalase and ascorbate peroxidadase enzymes and the amount of hydrogen peroxide and lipid peroxidation in seedlings with increasing extract concentration. The extract reduced the physiological quality of lettuce seeds and induced an increased production of hydrogen peroxide in seedlings, which increased the activity of antioxidant enzymes that were not effective in tissue detoxification, resulting in cellular damage and increased numbers of abnormal seedlings.

Predicting Delta Ferrite Content in Stainless Steel Castings

The distribution of delta ferrite fraction was measured with the magnetic method in specimens of different stainless steel compositions cast by the investment casting (lost wax) process. Ferrite fraction measurements published in the literature for stainless steel cast samples were added to the present work data, enabling an extensive analysis about practical methods to calculate delta ferrite fractions in stainless steel castings. Nineteen different versions of practical methods were formed using Schaeffler, DeLong, and Siewert diagrams and the nickel and chromium equivalent indexes suggested by several authors. These methods were evaluated by a detailed statistical analysis, showing that the Siewert diagram, including its equivalent indexes and iso-ferrite lines, gives the lowest relative errors between calculated and measured delta ferrite fractions. Although originally created for stainless steel welds, this diagram gives relative errors lower than those for the current ASTM standard method (800/A 800M-01), developed to predict ferrite fractions in stainless steel castings. Practical methods originated from a combination of different chromium/nickel equivalent indexes and the iso-ferrite lines from Schaeffler diagram give the lowest relative errors when compared with combinations using other iso-ferrite line diagrams. For the samples cast in the present work, an increase in cooling rate from 0.78 to 2.7 K/s caused a decrease in the delta ferrite fraction, but a statistical hypothesis test revealed that this effect is significant in only 50% of the samples that have ferrite in their microstructures.

OPTIMUM RATIO OF CALCIUM AND BORON IN THE NUTRIENT SOLUTION OR IN CASTOR BEAN SHOOT FOR FRUIT YIELD AND SEED OIL CONTENT

Calcium (Ca) and boron (B) have been reported as the major macro-and micronutrient required for castor bean plant yield. The objective of this study was to determine the Ca: B ratios (in the growth media and plant tissue) for fruit yield and shoot dry weight of the castor bean (Ricinus communis L.), grown in a nutrient solution, and to evaluate Ca and B supply on concentration and total uptake of Ca, potassium (K), magnesium (Mg), and B, as well on the seed oil content. The treatments were arranged in a 3 x 3 factorial fashion, consisting of three rates of Ca (40, 80, and 160 mg L-1) and three of B (0.32, 0.96, and 1.60 mg L-1). Calcium and B rates increased the shoot and root dry weight and fruit yield at a Ca: B ratio in the nutrient solution of 166 and 100, respectively. Symptoms of B deficiency were observed in plants supplied with 0.32 mg B L-1, regardless of the Ca concentration in the nutrient solution. Plants which showed visual symptoms of Ca deficiency cultivated with 40 mg Ca L-1 presented concentration of Ca in plant tissue up to 10 g kg(-1). The concentration and total Ca and B uptake increased with the rates of them. Notwithstanding, the shoot Ca accumulation was improved by B rates. In addition, there were no decreases in K and Mg uptake due to Ca rates. Furthermore, addition of 80 mg L-1 of Ca and 1.60 mg L-1 of B in the growth media increased the seed oil content. The Ca: B ratio in the diagnostic leaf associated with the highest plant dry weight (shoot and root) and fruit yield, was 500 (16 to 20 g kg(-1) of Ca, and for 30 to 40 mg kg(-1) of B).

Soil sulfur fractions dynamics and distribution in a tropical grass pasture amended with nitrogen and sulfur fertilizers

Soil sulfur (S) partitioning among the various pools and changes in tropical pasture ecosystems remain poorly understood. Our study aimed to investigate the dynamics and distribution of soil S fractions in an 8-year-old signal grass (Brachiaria decumbens Stapf.) pasture fertilized with nitrogen (N) and S. A factorial combination of two N rates (0 and 600?kg N ha1 y1, as NH4NO3) and two S rates (0 and 60?kg S ha1 y1, as gypsum) were applied to signal grass pastures during 2 y. Cattle grazing was controlled during the experimental period. Organic S was the major S pool found in the tropical pasture soil, and represented 97% to 99% of total S content. Among the organic S fractions, residual S was the most abundant (42% to 67% of total S), followed by ester-bonded S (19% to 42%), and C-bonded S (11% to 19%). Plant-available inorganic SO4-S concentrations were very low, even for the treatments receiving S fertilizers. Low inorganic SO4-S stocks suggest that S losses may play a major role in S dynamics of sandy tropical soils. Nitrogen and S additions affected forage yield, S plant uptake, and organic S fractions in the soil. Among the various soil fractions, residual S showed the greatest changes in response to N and S fertilization. Soil organic S increased in plots fertilized with S following the residual S fraction increment (16.6% to 34.8%). Soils cultivated without N and S fertilization showed a decrease in all soil organic S fractions.

Introducing Acacia mangium trees in Eucalyptus grandis plantations: consequences for soil organic matter stocks and nitrogen mineralization

Background and aims Eucalyptus plantations cover 20 million hectares on highly weathered soils. Large amounts of nitrogen (N) exported during harvesting lead to concerns about their sustainability. Our goal was to assess the potential of introducing A. mangium trees in highly productive Eucalyptus plantations to enhance soil organic matter stocks and N availability. Methods A randomized block design was set up in a Brazilian Ferralsol soil to assess the effects of mono-specific Eucalyptus grandis (100E) and Acacia mangium (100A) stands and mixed plantations (50A:50E)on soil organic matter stocks and net N mineralization. Results A 6-year rotation of mono-specific A. mangium plantations led to carbon (C) and N stocks in the forest floor that were 44% lower and 86% higher than in pure E. grandis stands, respectively. Carbon and N stocks were not significantly different between the three treatments in the 0-15 cm soil layer. Field incubations conducted every 4 weeks for the two last years of the rotation estimated net soil N mineralization in 100A and 100E at 124 and 64 kg ha(-1) yr(-1), respectively. Nitrogen inputs to soil with litterfall were of the same order as net N mineralization. Conclusions Acacia mangium trees largely increased the turnover rate of N in the topsoil. Introducing A. mangium trees might improve mineral N availability in soils where commercial Eucalyptus plantations have been managed for a long time.

Influence of caffeine on the survival of leaf-cutting ants Atta sexdens rubropilosa and in vitro growth of their mutualistic fungus

BACKGROUND: Leaf-cutting ants collect plant fresh material for the cultivation of their mutualistic fungus. Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae) cause great economic losses through their foraging activity, mainly in agriculture. The main control method is the application of granulated toxic baits incorporated with an active ingredient (AI). The present goal is to evaluate the effect of caffeine on in vitro growth of the mutualistic fungus and on the survival of the leaf-cutting ants, aiming to verify the potential toxicity of this secondary metabolite over these organisms. RESULTS: Three distinct patterns of fungal growth correlated with caffeine concentration were observed: (1) no effect (0.01% caffeine); (2) intermediate growth reduction (0.05% caffeine); (3) drastic growth reduction (0.10 and 0.50% caffeine). The highest caffeine concentration causes fungus death in the first week. As for insect survival, caffeine does not seem to exert any effect. The treatments with diet containing caffeine showed similar values of M50, irrespective of caffeine concentration. CONCLUSION: As caffeine was shown to reduce growth of the mutualistic fungus of Atta sexdens rubropilosa, but with no conclusive effect on insect survival, a hypothetical explanation for the selection of different Coffea species by this leaf-cutting ant species might be associated with caffeine toxicity to the fungus. Copyright (C) 2011 Society of Chemical Industry

The nitrogen sufficiency index underlying estimates of nitrogen fertilization requirements of common bean

Chlorophyll determination with a portable chlorophyll meter can indicate the period of highest N demand of plants and whether sidedressing is required or not. In this sense, defining the optimal timing of N application to common bean is fundamental to increase N use efficiency, increase yields and reduce the cost of fertilization. The objectives of this study were to evaluate the efficiency of N sufficiency index (NSI) calculated based on the relative chlorophyll index (RCI) in leaves, measured with a portable chlorophyll meter, as an indicator of time of N sidedressing fertilization and to verify which NSI (90 and 95 %) value is the most appropriate to indicate the moment of N fertilization of common bean cultivar Perola. The experiment was carried out in the rainy and dry growing seasons of the agricultural year 2009/10 on a dystroferric Red Nitosol, in Botucatu, São Paulo State, Brazil. The experiment was arranged in a randomized complete block design with five treatments, consisting of N managements (M1: 200 kg ha-1 N (40 kg at sowing + 80 kg 15 days after emergence (DAE) + 80 kg 30 DAE); M2: 100 kg ha-1 N (20 kg at sowing + 40 kg 15 DAE + 40 kg 30 DAE); M3: 20 kg ha-1 N at sowing + 30 kg ha-1 when chlorophyll meter readings indicated NSI < 95 %; M4: 20 kg ha-1 N at sowing + 30 kg ha-1 N when chlorophyll meter readings indicated NSI < 90 % and, M5: control (without N application)) and four replications. The variables RCI, aboveground dry matter, total leaf N concentration, production components, grain yield, relative yield, and N use efficiency were evaluated. The RCI correlated with leaf N concentrations. By monitoring the RCI with the chlorophyll meter, the period of N sidedressing of common bean could be defined, improving N use efficiency and avoiding unnecessary N supply to common bean. The NSI 90 % of the reference area was more efficient to define the moment of N sidedressing of common bean, to increase N use efficiency.