Effect of temperature and moisture on the dormancy and activation pattern of Oxalis latifolia bulbs

Con objeto de buscar información para un mejor control de Oxalis latifolia Kunth, se ha estudiado el efecto que presentan la temperatura y la humedad sobre la activación de sus bulbos, tanto en la forma común como en la forma Cornwall de la misma. Los bulbos de la mala hierba se mantuvieron en un refrigerador a +4°C durante 13, 20, 27, 41, 48 y 55 días. Se sacaron tres grupos de 30 bulbos de cada forma en cada fecha de muestreo y se colocaron a 21°C; 15 de ellos se mantuvieron en condiciones de sequía —no se regaron— y otros 15 en condiciones de humedad —añadiendo el agua necesaria—. Los resultados muestran que la activación ocurre durante un período prolongado de tiempo en ambas formas, tanto en seco como en húmedo. También se observó que los bulbos secos se activaron antes que los húmedos y los de la forma común antes que los Cornwall. Se observaron dos patrones de activación: los bulbos secos de la forma común generalmente presentaron una activación que sigue un patrón logarítmico, mientras que sus bulbos humedecidos mostraron una tendencia linear; los bulbos Cornwall se activaron con una tendencia exponencial en la mayoría de los casos. El tiempo medio requerido para la activación después del almacenamiento en frío fue constante en la forma común, sin embargo la activación de Cornwall fue más rápida cuanto más tiempo permanecieron almacenados en frío.

Effect of temperature and carpel size during pre-anthesis on potential grain weight in wheat

The effect of environmental conditions immediately before anthesis on potential grain weight was investigated in wheat at the experimental field of the Faculty of Agronomy (University of Buenos Aires, Argentina) during 1995 and 1996. Plants of two cultivars of wheat were grown in two environments (two contrasting sowing dates) to provide different background temperature conditions. In these environments, transparent boxes were installed covering the spikes in order to increase spike temperature for a short period (c. 6 days) immediately before anthesis, i.e. between ear emergence and anthesis. In both environments, transparent boxes increased mean temperatures by at least 3n8 mC. These increases were almost entirely due to the changes in maximum temperatures because minimum temperatures were little affected. Final grain weight was significantly reduced by higher temperature during the ear emergence–anthesis period. It is possible that this reduction could be mediated by the effect of the heat treatment on carpel weight at anthesis because a curvilinear association between final grain weight and carpel weight at anthesis was found. This curvilinear association may also indicate a threshold carpel weight for maximizing grain weight.

In vivo effect of flucloxacillin in experimental endocarditis caused by mecC-positive staphylococcus aureus showing temperature-dependent susceptibility in vitro.

Methicillin-resistant Staphylococcus aureus (MRSA) carrying the mecC gene (mecC-MRSA) exhibited at 37°C MICs of oxacillin close to those of methicillin-susceptible S. aureus (MSSA). We investigated whether at this temperature, mecC-MRSA strains respond to flucloxacillin treatment like MSSA strains, using a rat model of endocarditis. Flucloxacillin (human-like kinetics of 2 g intravenously every 6 h) cured 80 to 100% of aortic vegetations infected with five different mecC-MRSA strains. These results suggest that mecC-MRSA infections may successfully respond to treatment with β-lactams.

Effect of temperature on the electro-oxidation of ethanol on platinum

We present in this work an experimental investigation of the effect of temperature (from 25 to 180 ºC) in the electro-oxidation of ethanol on platinum in two different phosphoric acid concentrations. We observed that the onset potential for ethanol electro-oxidation shifts to lower values and the reaction rates increase as temperature is increased for both electrolytes. The results were rationalized in terms of the effect of temperature on the adsorption of reaction intermediates, poisons, and anions. The formation of oxygenated species at high potentials, mainly in the more diluted electrolyte, also contributes to increase the electro-oxidation reaction rate.

Ce - promoted catalyst from hydrotalcites for CO2 reforming of methane: calcination temperature effect

Ce-promoted Ni-catalysts from hydrotalcites were obtained. The effect of calcination temperature on the chemical and physical properties of the catalysts was studied. Several techniques were used to determine the chemical and physical characteristics of oxides. The apparent activation energies of reduction were determined. Catalytic experiments at 48 L g-1h-1 without pre-reduction in CO2 reforming of methane were performed. The spinel-like phase in these oxides was only formed at 1000 ºC. The reduction of Ni2+ in the oxides was clearly affected by the calcination temperature which was correlated with catalytic performance. The catalyst calcined at 700 ºC showed the greatest activity.

Effect of temperature, leaf wetness, and rainfall on the production of Guignardia citricarpa ascospores and on back spot severity on sweet orange

The black spot of citrus (Citrus sp.) is caused by Guignardia citricarpa with ascospore production depending on temperature, leaf wetness, and rainfall. The number of ascospores produced was monitored using a spore trap and climatic factors were recorded using an automated meteorological station of 'Natal' and 'Valencia' sweet orange (Citrus sinensis) orchards in Mogi Guaçu in the state of São Paulo, Brazil, from November 2000 to March 2001. The fruits were bagged to prevent infection and the bags removed from different sets of fruit for one week during each of the 18 weeks of the season in both orchards. Ascospores were produced during the entire experimental period, from spring through summer, primarily after rain events. In both orchards, ascospore production reached a peak in January and February. Ascospore production was related to leaf wetness only in the Natal orange orchard but was not related to total rainfall or temperature in either orchard. Disease was most severe on fruit exposed the 7th, 8th, and 13th weeks after beginning the experiment in both cultivars as well as after the 16th week for 'Natal'. There was a strong relationship between disease severity and total rainfall for both orchards and a weak correlation between temperature and severity in the 'Natal' block only. There was no relationship between severity and leaf wetness or ascospore numbers.

Effect of temperature, wetness duration and cultivar on the development of anthracnose in guava fruits

The development of a large number of postharvest diseases is closely associated with fruit ripeness. Environmental conditions may affect both the pathogen development and the fruit ripening rate. The aim of this study was to determine the most favorable temperature and wetness duration to the development of anthracnose in guava fruits. Cultivars 'Kumagai' (white pulp) and 'Pedro Sato' (red pulp) were inoculated with a conidial suspension of Colletotrichum gloeosporioides and C. acutatum and incubated at constant temperature ranging from 10 to 35ºC and wetness duration of 6 and 24 hours. Disease severity and incidence were evaluated at every two days during 12 days. No infection occurred at 10 and 35ºC, regardless of the wetness duration. The optimum conditions for fruit infection were 26 and 27ºC for 'Kumagai' and 25 and 26ºC for 'Pedro Sato', adopting 24 hours of wetness. In general, the disease development in 'Kumagai' cultivar was more affected by the wetness period, compared to 'Pedro Sato'. Disease severity for 'Kumagai' fruits was maximal between 25 and 30ºC , depending on the Colletotrichum species. Regarding 'Pedro Sato', the mean diameter of lesions was greater in fruits stored at 20, 25 and 30ºC , compared to 'Kumagai' cultivar, depending on the wetness period and the species. The incubation period (between 6 and 7 days) and the latent period (between 8 and 10 days) were minimal at 30ºC. The data generated in this study will be useful either for the development of a disease warning system or for the increase in the shelf life of guavas in the postharvest.

In vitro effect of substrate, temperature and photoperiod on Phakopsora pachyrhizi urediniospore germination and germ tube growth

In vitro experiments were conducted to assess the effects of substrate, temperature and time of exposure to temperature and photoperiod on P. pachyrhizi uredospore germination and germ tube growth. The following substrates were tested: water-agar and soybean leaf extract-agar at different leaf concentrations (0.5, 1.0, 2.0 and 4.0 g of leaves and 15g agar/L water), temperatures (10, 15, 20, 25, 30, and 35oC) and times of exposure (1, 2, 3, 4, 5, 6, 7, and 8 hours) to temperature and 12 different photoperiods. The highest germination and germ tube length was found for the soybean leaf extract agar. Maximum P. pachyrhizi uredospore germination was obtained at 21.8 and 22.3°C, and maximum germ tube growth at 21.4 and 22.1°C. The maximum uredospore germination was found at 6.4 hours exposure, while the maximum germ tube length was obtained at 7.7 h exposure. Regarding photoperiod, the maximum spore germination and the maximum uredospore germ tube length were found in the dark. Neither spore germination nor uredospore germ tube growth was completely inhibited by the exposure to continuous light.

Evaluation of the physiological quality of anadenenthera peregrina (L.) Speg. seeds during storage

The aim of this experiment was to evaluate the effect of storage temperature on the viability and vigour of A. peregrina seeds. Seeds of A. peregrina harvested in Viçosa-MG, in September 2005 were used. The seeds were stored in the Laboratory of Forest Seeds Analysis (LASF) of the Universidade Federal de Viçosa (UFV), in a cold chamber, under approximately 5ºC over150 days. The seeds were stored under 20ºC for 150 days more. Seed moisture was determined after oven-drying at 105 ± 3ºC for 24 hours. The seeds were analyzed monthly using germination, tetrazolium and electrical conductivity tests and Osmopriming during 300 days, with four repetitions of 25 seeds. A. peregrina seeds kept a constant percentage of germination and viable seeds under the tetrazolium test for five months of storage, under either 5ºC and 20ºC. The electrical conductivity test showed significant differences in relation to the storage period, proving to be more sensitive than the standard germination test. Seed priming in PEG -0,4 MPa solution was not efficient in recovering the viability and vigor of the stored seeds at 5ºC and 20ºC.

Effects of thermal environment and supplementation levels on the physiological parameters of moxotó goats in confined and semi-confined rising systems

The objective of this work was to determine the effect of environmental variables and supplementation levels on physiological parameters of Moxotó goats in confined and semi-confined rising systems, in the Brazilian semi-arid region. The semi-confined individuals were kept on a grass based diet during the day and arrested in the end of the afternoon. The confined animals were kept in a management center, receiving two diets composed by forage cactus and maniçoba hay into two different levels (0.5 and 1.5% of the body weight). Inside the management center and in the external environment the environmental comfort parameters were set high during the afternoon period characterizing a situation of thermal discomfort for the animals. During the morning the semi-confined animals presented an average respiratory frequency (69.5 mov min-1) and rectal temperature (39.5 ºC) higher than the confined ones (62.6 mov min-1 and 39.0 ºC, respectively). The confined and semi-confined animals were able to maintain their rectal temperature within normal limits, with increase in the cardiac beatings rate and respiratory frequency. The greater percentage of the used supplementations (1.5%) seemed to increase rectal temperature in the two studied rising systems.

Temperature effect in potassium and nitrate ions in soil transport

When doing researches on solute dynamics in porous medium, the knowledge of medium characteristics and percolating liquids, as well as of external factors is very important. An important external factor is temperature and, in this sense, our purpose was determining potassium and nitrate transport parameters for different values of temperature, in miscible displacement experiments. Evaluated parameters were retardation factor (R), diffusion/dispersion coefficient (D) and dispersivity, at ambient temperature (25 up to 28 ºC), 40 ºC and 50 ºC. Salts used were potassium nitrate and potassium chlorate, prepared in a solution made up of 5 ppm nitrate and 2.000 ppm potassium, with Red-Yellow Latosol porous medium. Temperature exhibited a positive influence upon porous medium solution and upon dispersion coefficient.

Behavior, performance and physiological parameters of pigs reared in deep bedding

An experiment was conducted to evaluate the behavior, performance and physiological parameters of pigs in different production systems. Twenty four animals in the growth phase were distributed in a randomized block design in three treatments: T1 - concrete floor, T2 - deep bedding with wood shaving, and T3 - deep bedding with coffee husks. The behavioral study was carried out by observing the animal behavior for an uninterrupted period of eight hours throughout seven weeks. The proportions of time spent in each behavior were characterized using the frequency histogram composition. Environmental (IBGTH), physiological (rectal and skin temperature and respiratory rate) and performance (weight gain, feed intake and feed conversion) parameters were measured in animals during the period. The production systems of deep bedding showed higher values of IBGTH. There was no effect of production systems evaluated on the performance parameters. Rectal temperature was higher in animals reared on deep bedding with coffee husks in relation to the concrete floor. The use of deep bedding benefited the behavior of piglets in the growth phase and it reduced the agonistic behavior among individuals.

Physiological evaluation of heat stress in gestating sows under different housing systems in bedding and concrete floor

The purpose of this paper was to observe the use of bedding (wood shavings) in physiological variables that indicate thermal stress in gestating sows. The experiment was conducted in order to evaluate the effect of two types of floor (concrete and wood shavings). Worse microclimatic conditions were observed in bedding systems (P<0.05), with an increase in temperature and enthalpy of 1.14 ºC and 2.37 kJ.kg dry air-1, respectively. The floor temperature at the dirty area was higher in the bedding presence in comparison to its absence. In spite of the worse microclimatic conditions in the bedding, the rectal temperature did not differ significantly (P>0.05) but the skin surface temperature was higher in the bedding systems. The same occurred with the respiratory rates. The physical characteristics of the floor material influenced the rate of heat loss by conductance. Estimated values were 35.04 and 7.99 W m-2 for the conductive heat loss between the animal and floor for treatments with or without bedding, respectively. The use of bedding in sow rearing has a negative impact on microclimatic conditions, what implies in thermoregulatory damages.

Effect of time-temperature binomial in obtaining biochemical oxygen demand of different wastewaters

Studies on the effects of temperature and time of incubation of wastewater samples for the estimation of biodegradable organic matter through the biochemical oxygen demand (BOD), that nowadays are rare, considering that the results of the classic study of STREETER & PHELPS(1925) have been accepted as standard. However, there are still questions how could be possible to reduce the incubation time; whether the coefficient of temperature (θ) varies with the temperature and with the type of wastewater and if it approaches 1.047. Aiming the elucidation of these questions, wastewater samples of dairy, swine and sewage treated in septic tanks were incubated at temperatures of 20, 30 and 35 °C, respectively for 5, 3.16 and 2.5 days. From the parameter of deoxygenation coefficient at 20 °C (k20), θ30 and θ35 were calculated. The results indicated that θ values changes with the type of wastewater, however does not vary in the temperature range between 30 and 35 °C, and that the use of 1.047 value did not implied significant differences in obtaining k in a determined T temperature. Thus, it is observed that the value of θ can be used to estimate the required incubation time of the samples at different temperatures.

Effect of light and temperature on germination and early growth of Vochysia tucanorum Mart., Vochysiaceae, in cerrado and forest soil under different radiation levels

Vochysia tucanorum Mart. (Vochysiaceae) is a very widely distributed species in the cerrado and forests in Brazil, from the State of Bahia to Paraná. Its seed germination was analysed under eight treatments using different conditions of light and temperature. Up to 73 days, at least ca. 93% of the seeds germinated in all treatments, except under alternating temperatures of 35°/10°C (62%). Light enhanced germination, except under constant temperature of 25°C when seeds are not photoblastic. At this temperature, the highest percentage of germination was found. Initial vegetative growth was analysed by comparing the effects of shading, by means of different percentages of full daylight (100%, 45%, 10.6%, 4.8%), and soils from cerrado and forest. During 123 days, no mortality was recorded and cotyledons persisted on the seedlings of all treatments. In general, the seedlings of V. tucanorum were found to be more or less indifferent to the soil from cerrado or forest and shading seems to promote height increment. However, total dry mass was larger under a radiation of 45% full daylight and smaller under extreme conditions (100% or 4.8% full daylight).