Effect of water stress on nitrogen fixation and nodule structure of common bean

The aim of this work was to investigate the effect of water stress on N2 fixation and nodule structure of two common bean (Phaseolus vulgaris L.) cultivars Carioca and EMGOPA-201. Plants were harvested after five and eight days of water stress. Carioca had lower nodule dry weight on both water stress periods; shoot dry weight was lower at five days water stress and did not differ from control after eight days stress. Both cultivars had lower nitrogenase activity than control after five and eight days water stress. For both cultivars, after eight days stress bacteroid membranes were damaged. Carioca presented more pronounced damage to infected tissue, with host cell vacuolation and loss of the peribacteroid membrane at five days after stress; at eight days after stress, there was degradation of cytoplasm host cells and senescence of bacteroids, with their release into intercellular spaces. Intensity of immunogold-labeling of intercellular cortical glycoprotein with the monoclonal antibodies MAC 236/265 was different for both cultivars.

Combining ability of maize grain yield under different levels of environmental stress

The objectives of this work were to caracterize the tropical maize germplasm and to compare the combining abilities of maize grain yield under different levels of environmental stress. A diallel was performed among tropical maize cultivars with wide adaptability, whose hybrid combinations were evaluated in two sowing dates, in two years. The significance of the environmental effect emphasized the environmental contrasts. Based on grain yield, the environments were classified as favorable (8,331 kg ha-1), low stress (6,637 kg ha-1), high stress (5,495 kg ha-1), and intense stress (2,443 kg ha-1). None of the genetic effects were significant in favorable and intense stress environments, indicating that there was low germplasm variability under these conditions. In low and high stresses, the specific combining ability effects (SCA) were significant, showing that the nonadditive genetic effects were the most important, and that it is possible to select parent pairs with breeding potential. SCA and grain yield showed significant correlations only between the closer environment pairs like favorable/low stress and high/intense stress. The genetic control of grain yield differed under contrasting stress environments for which maize cultivars with wide adaptability are not adequate.

Physiological indicators of stress in gestating sows under different cooling systems

The objective of this work was to determine physiological stress markers, neutrophil:lymphocyte ratio (N/L) and corticoid concentrations, in gestating sows under different cooling systems. A sprinkling cooling system (SS) and a system based on fan-assisted evaporative cellulose pad (PS) were used. SS showed higher N/L ratio (1.095) than PS (0.850). Corticoid concentrations showed high variability. Corticosteroids are more efficient short-term stress indicators while N/L ratio is a good medium and long-term stress indicator. According to N/L ratio, gestating sows under PS benefit from a higher level of welfare.

Water stress before harvest of pepper-rosmarin

The objective of this work was to assess the effect of different periods of water stress before harvest of pepper-rosmarin (Lippia sidoides) on the contents of essential oil and flavonoids. The experiment was carried out during 270 days of cultivation, with drainage lysimeters, in a completely randomized block design with five treatments: 0, 2, 4, 6, and 8 days of water suppression before harvest, with four replicates. Fresh and dry matter yield, essential oil content, total flavonoids content, and water potential and temperature of leaves were determined. There was a decrease of approximately 50% in oil content and of 60% in total flavonoid content with the reduction of leaf water potential in 0.3 MPa. Essential oil is more sensitive to water stress than total flavonoids.

Growth and stress of dourado cultivated in cages at different stocking densities

The objective of this work was to evaluate the growth and the stress levels of juvenile dourado (Salminus brasiliensis) cultivated in cages. Fish stocked at densities of 15 (D15) and 30 (D30) fish per square meter were evaluated in a completely randomized design with three replicates. Fish were fed twice a day with extruded ration (42% crude protein). Density influenced only biomass and daily food intake, and glucose and lactate concentrations increased over time. D15 and D30 did not influence the growth of dourado. However, the increase of glucose and lactate levels over time indicates that cultivation in cages is a stressful condition for this species.

Salt stress change chlorophyll fluorescence in mango

This study evaluated the tolerance of mango cultivars 'Haden', 'Palmer', 'Tommy Atkins' and 'Uba' grafted on rootstock 'Imbú' to salt stress using chlorophyll fluorescence. Plants were grown in modified Hoagland solution containing 0, 15, 30, and 45 mmol L-1 NaCl. At 97 days the parameters of the chlorophyll fluorescence (F0, Fm, Fv, F0/Fm, Fv/Fm, Fv'/Fm', ΦPSII = [(Fm'-Fs)/(Fm')], D = (1- Fv'/Fm') and ETR = (ΦPSII×PPF×0,84×0,5) were determined. At 100 days, the leaf emission and leaf area, toxicity and leaf abscission indexes were determined. In all cultivars evaluated, in different degree, there were decreases in photochemical efficiency of photosystem II, enhanced concentrations from 15 mmol L-1 NaCl. The decreases in the potential quantum yield of photosystem II (Fv/Fm) were 27.9, 18.7, 20.5, and 27.4%, for cultivars 'Haden', 'Palmer', 'Tommy Atkins', and 'Uba', respectively, when grown in 45 mmol L-1 NaCl. It was found decreases in leaf emission and mean leaf area in all cultivars from 15 mmol L-1 NaCl. There were increases in leaf toxicity of 33.0, 67.5, 41.6 and 80.8% and in leaf abscission of 71.8, 29.2, 32.5, and 67.9% for the cultivars 'Haden', 'Palmer', 'Tommy Atkins', and 'Uba' respectively, when grown in 45 mmol L-1 NaCl. Leaf toxicity and leaf abscission were not observed in 15 mmol L-1 NaCl. The decrease in Fv/Fm ratio were accompanied by decreasing in leaf emission and increased leaf toxicity index, showing, therefore, the potential of chlorophyll fluorescence in the early detection of salt stress in mango tree.

PREDICTING THE BOILING POINT OF PCDD/Fs BY THE QSPR METHOD BASED ON THE MOLECULAR DISTANCE-EDGE VECTOR INDEX

The quantitative structure property relationship (QSPR) for the boiling point (Tb) of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) was investigated. The molecular distance-edge vector (MDEV) index was used as the structural descriptor. The quantitative relationship between the MDEV index and Tb was modeled by using multivariate linear regression (MLR) and artificial neural network (ANN), respectively. Leave-one-out cross validation and external validation were carried out to assess the prediction performance of the models developed. For the MLR method, the prediction root mean square relative error (RMSRE) of leave-one-out cross validation and external validation was 1.77 and 1.23, respectively. For the ANN method, the prediction RMSRE of leave-one-out cross validation and external validation was 1.65 and 1.16, respectively. A quantitative relationship between the MDEV index and Tb of PCDD/Fs was demonstrated. Both MLR and ANN are practicable for modeling this relationship. The MLR model and ANN model developed can be used to predict the Tb of PCDD/Fs. Thus, the Tb of each PCDD/F was predicted by the developed models.

Callus cell culture of Pothomorphe umbellata (L.) under stress condition leads to high content of peroxidase enzyme

Pothomorphe umbellata (L.) known on Brazil as Caapeba has a number of popular medicinal use, and it has been studied in relation to its pharmacological activity. Peroxidase specific activity (units/mg protein) was evaluated in callus cell culture samples of the P.umbellata, grown in two different MS medium (media 1 and media 2), submitted to 16 hours photoperiod or kept in darkness. Cell growth rate curve showed that the best growth indices were observed when media 2 submitted to the photoperiod regime was used, followed by the same media kept in darkness (stress condition). The results obtained also showed that the cell culture grown under stress conditions (darkness) lead to high content of peroxidase enzyme (an increase of 700% was observed). Kinetic constant values of 3.3 mmol.L-1 and 2,8 sec-1 were obtained for kM and v max,, respectively, using guaiacol as enzyme substrate.

Relationships and estimates of longitudinal growth stress in Eucalyptus dunnii at different ages

The objective of this study was to obtain estimates of longitudinal growth stresses in standing trees of the Eucalyptus dunnii Maiden at eight, thirteen, fifteen and nineteen years of age and to determine their relationships with wood characteristics. The longitudinal growth stresses were indirectly measured by the "CIRAD-Forêt" method and estimated from both the dynamic modulus of elasticity and the modulus of elasticity in tension parallel to the grain. The longitudinal residual strain (LRS) and the estimates of the longitudinal growth stresses tended to increase with the age of the material. The LRS correlated positively and significantly with all the growth stresses estimates. The largestes magnitudes were at 13, 15 and 19 years of age. The basic density presented high, positive and significant correlations with the dynamic modulus of elasticity, estimated in the longitudinal direction, for wood saturated and at 12% moisture content, for all the ages assessed. All the growth stresses estimates presented high, positive and significant correlations between themselves.

Determinação do módulo de elasticidade em madeira laminada colada por meio de ensaio não destrutivo (''stress wave timer'')

As vigas estruturais de madeira são formas racionais do emprego da madeira na construção de estruturas, sendo obtidas pela associação de peças serradas e permitindo a utilização de tábuas com seções e comprimentos variados, além de combinações com madeira de qualidade diferenciada. Para atingir a resistência máxima de uma viga de madeira laminada colada, pode-se utilizar a classificação mecânica das peças por meio dinâmico. O objetivo deste estudo foi estabelecer correlação entre os métodos estático e dinâmico de classificação de vigas de madeira laminada. O trabalho foi desenvolvido com o emprego de peças de madeira serrada de Pinus taeda e adesivo resorcina fenolformaldeído. O processo de fabricação das vigas envolveu a classificação das peças, usinagem de emendas, formação das lamelas, montagem e prensagem das vigas. Já os ensaios envolveram a determinação do módulo de elasticidade por meio do ''stress wave method'' e de uma máquina universal de ensaios. Os resultados foram analisados pela análise de regressão do estabelecimento da equação de ajuste de correlação. O sistema de classificação visual utilizado na seleção de peças foi insuficiente para se atingirem os valores máximos de módulo de elasticidade; o posicionamento correto das lamelas por meio do método dinâmico de classificação teve como consequência direta o aumento do módulo de elasticidade da viga, e houve baixa correlação entre as formas de obtenção do módulo de elasticidade das vigas, não sendo possível a elaboração de equação adequada entre os métodos testados.

Does the edge effect influence plant community structure in a tropical dry forest?

Edge effects are considered a key factor in regulating the structure of plant communities in different ecosystems. However, regardless to few studies, edge influence does not seem to be decisive in semiarid regions such as the Brazilian tropical dry forest known as Caatinga but this issue remains inconclusive. The present study tests the null hypothesis that the plant community of shrubs and trees does not change in its structure due to edge effects. Twenty-four plots (20 x 20 m) were set up in a fragment of Caatinga, in which 12 plots were in the forest edges and 12 plots were inside the fragment. Tree richness, abundance and species composition did not differ between edge and interior plots. The results of this study are in agreement with the pattern previously found for semiarid environments and contrasts with previous results obtained in different environments such as Rainforests, Savanna and Forest of Araucaria, which indicate abrupt differences between the border and interior of the plant communities in these ecosystems, and suggest that the community of woody plants of the Caatinga is not ecologically affected by the presence of edges.

Estimativas das propriedades de compostos LVL produzidos com paricá (Schizolobium amazonicum Huber ex Ducke) por meio de stress wave

Foram avaliadas as propriedades físicas e mecânicas de compósitos LVL produzidos com a madeira de paricá (Schizolobium amazonicum Huber ex. Ducke), por meio de Stress Wave Timer. Os compósitos foram confeccionados em laboratório, dos quais foram retiradas amostras, que foram inicialmente destinadas à realização dos ensaios não destrutivos. Todas as amostras, com dimensões de 2,2 × 2,2 × 40 cm, foram ensaiadas, não destrutivamente, com a propagação de ondas nos sentidos flatwise e edgewise. Em sequência, as mesmas amostras foram destinadas à confecção de subamostras, para realização dos ensaios destrutivos, físicos (absorção de água, inchamento em espessura e inchamento residual) e mecânicos (resistência e rigidez à flexão estática flatwise; resistência e rigidez à flexão estática edgewise; resistência à compressão paralela e resistência ao cisalhamento paralelo e perpendicular). A velocidade de propagação das ondas (V0) e o módulo de elasticidade dinâmico (Emd), obtidos com o auxílio do Stress Wave, foram utilizados para elaboração de modelos de predição das propriedades avaliadas. Os resultados indicaram que o Stress Wave Timer apresenta resultados satisfatórios para predição das propriedades mecânicas de compósitos LVL. Com relação às propriedades físicas, embora tenham sido verificados modelos com ajustes significativos, constatou-se limitação dessa ferramenta para predição desses parâmetros. Contudo, considerando ambas as propriedades, físicas e mecânicas, os melhores ajustes foram observados em amostras ensaiadas com a propagação de ondas no sentido edgewise e com o uso da variável independente Emd.

Efficiency of distinct data mining algorithms for classifying stress level in piglets from their vocalization

Among the challenges of pig farming in today's competitive market, there is factor of the product traceability that ensures, among many points, animal welfare. Vocalization is a valuable tool to identify situations of stress in pigs, and it can be used in welfare records for traceability. The objective of this work was to identify stress in piglets using vocalization, calling this stress on three levels: no stress, moderate stress, and acute stress. An experiment was conducted on a commercial farm in the municipality of Holambra, São Paulo State , where vocalizations of twenty piglets were recorded during the castration procedure, and separated into two groups: without anesthesia and local anesthesia with lidocaine base. For the recording of acoustic signals, a unidirectional microphone was connected to a digital recorder, in which signals were digitized at a frequency of 44,100 Hz. For evaluation of sound signals, Praat® software was used, and different data mining algorithms were applied using Weka® software. The selection of attributes improved model accuracy, and the best attribute selection was used by applying Wrapper method, while the best classification algorithms were the k-NN and Naive Bayes. According to the results, it was possible to classify the level of stress in pigs through their vocalization.

Citrus root distribution under water stress grown in sandy soil of central Florida

The experiment was conducted in an orchard located in University of Florida (Citrus Research and Education Center), Lake Alfred, Polk County, Florida, USA. The objective of this study was to evaluate the effects of water stress in root distribution of 'Valencia' orange tree on 'Swingle' citrumelo rootstock. Three treatments were imposed on the trees: 1) normal irrigation with microsprinklers, 2) no irrigation in winter (November through mid-March) and 3) rainfall exclusion by placing a water repelling fabric (Tyvek) under the trees. Trees in treatments 1 and 2 received normal rainfall during the winter, but treatment 3 received no rain. Normal irrigation was resumed on all treatments in mid March. Soil was collected using root auger head (0.09 m diameter and height 0.25 m) in two opposing quadrants (West and East at 3 horizontal distances from tree trunk (1, 2 and 3 m) and 4 depths (0.0-0.15; 0.15-0.30; 0.30-0.60 and 0.60-0.90 m). The results from root sampling showed that there was a significant difference in root distribution between irrigated treatment and non irrigated/non rainfall.