A natural structural variant of the mouse TCR beta-chain displays intrinsic receptor function and antigen specificity.

The Cbeta0 alternate cassette exon is located between the Jbeta1 and Cbeta1 genes in the mouse TCR beta-locus. In T cells with a VDJbeta1 rearrangement, the Cbeta0 exon may be included in TCRbeta transcripts (herein called TCRbeta-Cbeta0 transcripts), potentially inserting an additional 24 aa between the V and C domains of the TCR beta-chain. These TCRbeta splice isoforms may be differentially regulated after Ag activation, because we detected TCRbeta-Cbeta0 transcripts in a high proportion (>60%) of immature and mature T cells having VDJbeta1 rearrangements but found a substantially reduced frequency (<35%) of TCRbeta-Cbeta0 expression among CD8 T cells selected by Ag in vivo. To study the potential activity of the TCRbeta-Cbeta0 splice variant, we cloned full-length TCR cDNAs by single-cell RT-PCR into retroviral expression vectors. We found that the TCRbeta-Cbeta0 splice isoform can function during an early stage of T cell development normally dependent on TCR beta-chain expression. We also demonstrate that T hybridoma-derived cells expressing a TCRbeta-Cbeta0 isoform together with the clonally associated TCR alpha-chain recognize the same cognate peptide-MHC ligand as the corresponding normal alphabetaTCR. This maintenance of receptor function and specificity upon insertion of the Cbeta0 peptide cassette signifies a remarkable adaptability for the TCR beta-chain, and our findings open the possibility that this splice isoform may function in vivo.

Brachiaria sp yield and nutrient contents after nitrogen and sulphur fertilization

Among the production factors, adequate fertilization is an important tool to raise the productivity of pastoral systems and consequently increase the share of Brazil in the supply chain of primary agricultural products at the global level. The objective of this study was to evaluate the interaction of nitrogen and sulfur fertilization in BRACHIARIA DECUMBENS: Stapf. The experiment in pots with Dystrophic Oxisol was evaluated in a completely randomized design with four replications in a 5 x 3 factorial arrangement, involving five N doses (0, 100, 200, 400, and 800 mg dm-3) in the form of ammonium nitrate and three S doses (0, 20 and 80 mg dm-3) in the form of calcium sulfate, with a total of 15 treatments. In the treatments with low S dose, calcium was provided as calcium chloride, to ensure a homogeneous Ca supply in all treatments. The results showed that the tiller production and dry weight of green leaves and of stems + sheaths and total dry weight were favored by the combination of N and S fertilizer, while the proportion of dry leaves was reduced. Nitrogen fertilization raised the N contents in green leaves and stems + sheaths and reduced K contents in fresh and dry leaves. The response to S rates in the N content of green leaves was quadratic.

Wheat yield and physical properties of a brown latosol under no-tillage in south-central Paraná

Soil management influences the chemical and physical properties of soil. Chemical conditions have been thoroughly studied, while the role of soil physical conditions regarding crop yield has been neglected. This study aimed to analyze the wheat yield and its relationship with physical properties of an Oxisol under no-tillage (NT). The study was carried out between 2010 and 2011, in Reserva do Iguaçu, State of Paraná, Brazil, on the Campo Bonito farm, after 25 years of NT management. Based on harvest maps of barley (2006), wheat (2007) and maize (2009) of a plot (150 ha), zones with higher and lower yield potential (Z1 and Z2, respectively) were identified. Sampling grids with 16 units (50 x 50 m) and three sampling points per unit were established. The wheat grain yield (GY) and water infiltration capacity (WIC) were evaluated in 2010. Soil samples with disturbed and undisturbed structure were collected from the 0.00-0.10 and 0.10-0.20 m layers. The former were used to determine soil organic carbon (Corg) levels and the latter to determine soil bulk density (BD), total porosity (TP), macroporosity (Mac), and microporosity (Mic). Soil penetration resistance (PR) and water content (SWC) were also evaluated. The wheat GY of the whole plot was close to the regional average and the yield between the zones differed significantly, i.e. 22 % higher in Z1 than in Z2. No significant variation in Mic was observed between zones, but Z1 had higher Corg levels, SWC, TP and Mac and lower BD than Z2 in both soil layers, as well as a lower PR than Z2 in the 0.00-0.10 m layer. Therefore, soil physical conditions were more restrictive in Z2, in agreement with wheat yield and zone yield potential defined a priori, based on the harvest maps. Soil WIC in Z1 was significantly higher (30 %) than in Z2, in agreement with the results of TP and Mac which were also higher in Z1 in both soil layers. The correlation analysis of data of the two layers showed a positive relationship between wheat GY and the soil properties TP, SWC and WIC.

Optical crop sensor for variable-rate nitrogen fertilization in corn: II - indices of fertilizer efficiency and corn yield

Generally, in tropical and subtropical agroecosystems, the efficiency of nitrogen (N) fertilization is low, inducing a temporal variability of crop yield, economic losses, and environmental impacts. Variable-rate N fertilization (VRF), based on optical spectrometry crop sensors, could increase the N use efficiency (NUE). The objective of this study was to evaluate the corn grain yield and N fertilization efficiency under VRF determined by an optical sensor in comparison to the traditional single-application N fertilization (TSF). With this purpose, three experiments with no-tillage corn were carried out in the 2008/09 and 2010/11 growing seasons on a Hapludox in South Brazil, in a completely randomized design, at three different sites that were analyzed separately. The following crop properties were evaluated: aboveground dry matter production and quantity of N uptake at corn flowering, grain yield, and vegetation index determined by an N-Sensor® ALS optical sensor. Across the sites, the corn N fertilizer had a positive effect on corn N uptake, resulting in increased corn dry matter and grain yield. However, N fertilization induced lower increases of corn grain yield at site 2, where there was a severe drought during the growing period. The VRF defined by the optical crop sensor increased the apparent N recovery (NRE) and agronomic efficiency of N (NAE) compared to the traditional fertilizer strategy. In the average of sites 1 and 3, which were not affected by drought, VRF promoted an increase of 28.0 and 41.3 % in NAE and NRE, respectively. Despite these results, no increases in corn grain yield were observed by the use of VRF compared to TSF.

Soil physical properties and grape yield influenced by cover crops and management systems

The use of cover crops in vineyards is a conservation practice with the purpose of reducing soil erosion and improving the soil physical quality. The objective of this study was to evaluate cover crop species and management systems on soil physical properties and grape yield. The experiment was carried out in Bento Gonçalves, RS, Southern Brazil, on a Haplic Cambisol, in a vineyard established in 1989, using White and Rose Niagara grape (Vitis labrusca L.) in a horizontal, overhead trellis system. The treatments were established in 2002, consisting of three cover crops: spontaneous species (SS), black oat (Avena strigosa Schreb) (BO), and a mixture of white clover (Trifolium repens L.), red clover (Trifolium pratense L.) and annual rye-grass (Lolium multiflorum L.) (MC). Two management systems were applied: desiccation with herbicide (D) and mechanical mowing (M). Soil under a native forest (NF) area was collected as a reference. The experimental design consisted of completely randomized blocks, with three replications. The soil physical properties in the vine rows were not influenced by cover crops and were similar to the native forest, with good quality of the soil structure. In the inter-rows, however, there was a reduction in biopores, macroporosity, total porosity and an increase in soil density, related to the compaction of the surface soil layer. The M system increased soil aggregate stability compared to the D system. The treatments affected grapevine yield only in years with excess or irregular rainfall.

Sugarcane trash management assessed by the interaction of yield with soil properties

Currently, sugarcane plays an important global role, particularly with a view to alternative energy sources. Thus, in a sugarcane field of the mill Vale do Paraná S/A Álcool e Açúcar, Rubineia, São Paulo State, managed under two green cane harvest systems (cane trash left on and cane trash removed from the soil), Pearson and spatial correlations between the sugarcane yield (variety RB855035 in the third cut) and soil physical and chemical properties were studied to identify the property best correlated with stalk yield and the best harvest method. For this purpose, two geostatistical grids (121 sampling points on 1.30 ha) were installed on a eutrophic Red Argisol (homogeneous slope of 0.065 m m-1), in 2011, to determine the properties: stalk yield and sugarcane plant population, and soil resistance to penetration, gravimetric moisture, bulk density, and carbon stock, in the layers 0-0.20 and 0.20-0.40 m. The data were analyzed by descriptive, linear correlation and geostatistical analysis. In both treatments, the property stand density was best correlated with sugarcane yield (r = 0.725 in the trash mulching treatment - TM and r = 0.769 in the trash removal treatment - TR). However, in relation to the soil properties, bulk density (0-0.20 m) was best correlated (r = 0.305 in TM, r = 0.211 in TR). Similarly, from the spatial point of view, stand density was the property that best explained the sugarcane yield. However, in the TM treatment the density (0.20-0.40 m) was the only soil property spatially correlated with stalk yield. The carbon stock in the soil of the TM was 11.5 % higher than in the TR treatment. Results of the TM treatment were best, also with regard to soil management and conservation.

Rice straw incorporated just before soil flooding increases acetic acid formation and decreases available nitrogen

Incorporation of rice straw into the soil just before flooding for water-seeded rice can immobilize mineral nitrogen (N) and lead to the production of acetic acid harmful to the rice seedlings, which negatively affects grain yield. This study aimed to evaluate the formation of organic acids and variation in pH and to quantify the mineral N concentration in the soil as a function of different times of incorporation of rice straw or of ashes from burning the straw before flooding. The experiment was carried out in a greenhouse using an Inceptisol (Typic Haplaquept) soil. The treatments were as follows: control (no straw or ash); incorporation of ashes from previous straw burning; rice straw incorporated to drained soil 60 days before flooding; straw incorporated 30 days before flooding; straw incorporated 15 days before flooding and straw incorporated on the day of flooding. Experimental units were plastic buckets with 6.0 kg of soil. The buckets remained flooded throughout the trial period without rice plants. Soil samples were collected every seven days, beginning one day before flooding until the 13th week of flooding for determination of mineral N- ammonium (NH4+) and nitrate (NO3-). Soil solution pH and concentration of organic acids (acetic, propionic and butyric) were determined. All NO3- there was before flooding was lost in approximately two weeks of flooding, in all treatments. There was sigmoidal behavior for NH4+ formation in all treatments, i.e., ammonium ion concentration began to rise shortly after soil flooding, slightly decreased and then went up again. On the 91st day of flooding, the NH4+ concentrations in soil was 56 mg kg-1 in the control treatment, 72 mg kg-1 for the 60-day treatment, 73 mg kg-1 for the 30-day treatment and 53 mg kg-1 for the ash incorporation treatment. These ammonium concentrations correspond to 84, 108, 110 and 80 kg ha-1 of N-NH4+, respectively. When the straw was incorporated on the day of flooding or 15 days before, the concentration of N-NH4+ in the soil was 28 and 54 mg kg-1, equivalent to an accumulation of 42 and 81 kg ha-1 of N-NH4+, respectively. There was formation of acetic acid in which toxic concentrations were reached (7.2 mmol L-1) on the 15th day of flooding only for the treatment with straw incorporated on the day of flooding. The pH of the soil solution of all the treatments increased after flooding and this increase was faster in the treatments with incorporation of straw, followed by the ash treatment and then the control. After 60 days of flooding, however, the pH values were around 6.5 for all treatments, except for the control, which reached a pH of 6.3. Rice straw should be incorporated into the soil at least 30 days before flooding; otherwise, it may immobilize part of the mineral N and produce acetic acid in concentrations toxic to rice seedlings.

Evaluation of ammonia volatilization losses by adjusted parameters of a logistic function

The dynamics of N losses in fertilizer by ammonia volatilization is affected by several factors, making investigation of these dynamics more complex. Moreover, some features of the behavior of the variable can lead to deviation from normal distribution, making the main commonly adopted statistical strategies inadequate for data analysis. Thus, the purpose of this study was to evaluate the patterns of cumulative N losses from urea through ammonia volatilization in order to find a more adequate and detailed way of assessing the behavior of the variable. For that reason, changes in patterns of ammonia volatilization losses as a result of applying different combinations of two soil classes [Planossolo and Chernossolo (Typic Albaqualf and Vertic Argiaquolls)] and different rates of urea (50, 100 and 150 kg ha-1 N), in the presence or absence of a urease inhibitor, were evaluated, adopting a 2 × 3 × 2 factorial design with four replications. Univariate and multivariate analysis of variance were performed using the adjusted parameter values of a logistic function as a response variable. The results obtained from multivariate analysis indicated a prominent effect of the soil class factor on the set of parameters, indicating greater relevance of soil adsorption potential on ammonia volatilization losses. Univariate analysis showed that the parameters related to total N losses and rate of volatilization were more affected by soil class and the rate of urea applied. The urease inhibitor affected only the rate and inflection point parameters, decreasing the rate of losses and delaying the beginning of the process, but had no effect on total ammonia losses. Patterns of ammonia volatilization losses provide details on behavior of the variable, details which can be used to develop and adopt more accurate techniques for more efficient use of urea.

Soybean root growth and crop yield in reponse to liming at the beginning of a no-tillage system

Analyzing the soil near crop roots may reveal limitations to growth and yield even in a no-tillage system. The purpose of the present study was to relate the chemical and physical properties of soil under a no-tillage system to soybean root growth and plant yield after five years of use of different types of limestone and forms of application. A clayey Oxisol received application of dolomitic and calcitic limestones and their 1:1 combination in two forms: surface application, maintained on the soil surface; and incorporated, applied on the surface and incorporated mechanically. Soil physical properties (resistance to mechanical penetration, soil bulk density and soil aggregation), soil chemical properties (pH, exchangeable cations, H+Al, and cation exchange capacity) and plant parameters (root growth system, soybean grain yield, and oat dry matter production) were evaluated five years after setting up the experiment. Incorporation of lime neutralized exchangeable Al up to a depth of 20 cm without affecting the soil physical properties. The soybean root system reached depths of 40 cm or more with incorporated limestone, increasing grain yield an average of 31 % in relation to surface application, which limited the effect of lime up to a depth of 5 cm and root growth up to 20 cm. It was concluded that incorporation of limestone at the beginning of a no-tillage system ensures a favorable environment for root growth and soybean yield, while this intervention does not show long-term effects on soil physical properties under no-tillage. This suggests that there is resilience in the physical properties evaluated.

Human epidermal stem cell function is regulated by circadian oscillations.

Human skin copes with harmful environmental factors that are circadian in nature, yet how circadian rhythms modulate the function of human epidermal stem cells is mostly unknown. Here we show that in human epidermal stem cells and their differentiated counterparts, core clock genes peak in a successive and phased manner, establishing distinct temporal intervals during the 24 hr day period. Each of these successive clock waves is associated with a peak in the expression of subsets of transcripts that temporally segregate the predisposition of epidermal stem cells to respond to cues that regulate their proliferation or differentiation, such as TGFβ and calcium. Accordingly, circadian arrhythmia profoundly affects stem cell function in culture and in vivo. We hypothesize that this intricate mechanism ensures homeostasis by providing epidermal stem cells with environmentally relevant temporal functional cues during the course of the day and that its perturbation may contribute to aging and carcinogenesis.

Least limiting water range in assessing compaction in a Brazilian Cerrado latosol growing sugarcane

In the south-central region of Brazil, there is a trend toward reducing the sugarcane inter-harvest period and increasing traffic of heavy harvesting machinery on soil with high water content, which may intensify the compaction process. In this study, we assessed the structural changes of a distroferric Red Latosol (Oxisol) by monitoring soil water content as a function of the Least Limiting Water Range (LLWR) and quantified its effects on the crop yield and industrial quality of the first ratoon crop of sugarcane cultivars with different maturation cycles. Three cultivars (RB 83-5054, RB 84-5210 and RB 86-7515) were subjected to four levels of soil compaction brought about by a differing number of passes of a farm tractor (T0 = soil not trafficked, T2 = 2 passes, T10 = 10 passes, and T20 = 20 passes of the tractor in the same place) in a 3 × 4 factorial arrangement with three replications. The deleterious effects on the soil structure from the farm machinery traffic were limited to the surface layer (0-10 cm) of the inter-row area of the ratoon crop. The LLWR dropped to nearly zero after 20 tractor passes between the cane rows. We detected differences among the cultivars studied; cultivar RB 86-7515 stood out for its industrial processing quality, regardless of the level of soil compaction. Monitoring of soil moisture in the crop showed exposure to water stress conditions, although soil compaction did not affect the production variables of the sugarcane cultivars. We thus conclude that the absence of traffic on the plant row maintained suitable soil conditions for plant development and may have offset the harmful effects of soil compaction shown by the high values for bulk density between the rows of the sugarcane cultivars.

Impact of global warming on potato late blight : risk, yield loss and control

Selostus: Ilmaston lämpenemisen vaikutus perunaruttoon

In defense of the "tunneling" wave function of the universe

The tunneling approach to the wave function of the Universe has been recently criticized by Bousso and Hawking who claim that it predicts a catastrophic instability of de Sitter space with respect to pair production of black holes. We show that this claim is unfounded. First, we argue that different horizon size regions in de Sitter space cannot be treated as independently created, as they contend. And second, the WKB tunneling wave function is not simply the inverse of the Hartle-Hawking one, except in very special cases. Applied to the related problem of pair production of massive particles, we argue that the tunneling wave function leads to a small constant production rate, and not to a catastrophe as the argument of Bousso and Hawking would suggest.

Yield gains of coffee plants from phosphorus fertilization may not be generalized for high density planting

Inconclusive responses of the adult coffee plant to phosphorus fertilization have been reported in the literature, especially when dealing with application of this nutrient in high density planting systems. Thus, this study was carried out for the purpose of assessing the response of adult coffee plants at high planting density in full production (in regard to yield and their biennial cycle/stability) to the addition of different sources and application rates of P in the Zona da Mata region of Minas Gerais, Brazil. The experiment with coffee plants of the Catucaí Amarelo 6/30 variety was carried out over four growing seasons. Treatments were arranged in a full factorial design [(4 × 3) + 1] consisting of four P sources (monoammonium phosphate, simple superphosphate, natural reactive rock phosphate from Algeria (Djebel-Onk), and FH 550®), three P rates (100, 200, and 400 kg ha-1 year-1 of P2O5), and an additional treatment without application of the nutrient (0 kg ha-¹ year-¹). A randomized block experimental design was used with three replicates. The four seasons were evaluated as subplots in a split plot experiment. The P contents in soil and leaves increased with increased rates of P application. However, there was no effect from P application on the yield and its biennial cycle/stability regardless of the source used over the four seasons assessed.