Exposition Period Research Articles

Spring frost vulnerability of sweet cherries under controlled conditions.

Spring frost is a significant production hazard in nearly all temperate fruit-growing regions. Sweet cherries are among the first fruit varieties starting their development in spring and therefore highly susceptible to late frost. Temperatures at which injuries are likely to occur are widely published, but their origin and determination methods are not well documented. In this study, a standardized method was used to investigate critical frost temperatures for the sweet cherry cultivar 'Summit' under controlled conditions. Twigs were sampled at four development stages ("side green," "green tip," "open cluster," "full bloom") and subjected to three frost temperatures (-2.5, -5.0, -10.0°C). The main advantage of this method, compared to other approaches, was that the exposition period and the time interval required to reach the target temperature were always constant (2h). Furthermore, then, the twigs were placed in a climate chamber until full bloom, before the examination of the flowers and not further developed buds started. For the first two sampling stages (side green, green tip), the number of buds found in open cluster, "first white," and full bloom at the evaluation date decreased with the strength of the frost treatment. The flower organs showed different levels of cold hardiness and became more vulnerable in more advanced development stages. In this paper, we developed four empirical functions which allow calculating possible frost damages on sweet cherry buds or flowers at the investigated development stages. These equations can help farmers to estimate possible frost damages on cherry buds due to frost events. However, it is necessary to validate the critical temperatures obtained in laboratory with some field observations.

Характеристика сульфатвідновлювальних бактерій, виділених із техногенних екотопів

The metabolic and corrosion activity of sulfate-reducing bacteria isolated from technogenic ecotopes was investigated. The sulfate-reducing bacteria had significant hydrogen sulfide production (representatives of Desulfovibri о genus had synthesized hydrogen sulfide up to 430±14–475±23 mg/L, Desulfotomaculum genus – 410±16–460±20 mg/L. Strain Desulfomicrobium sp. ТС4 had the highest production of this compound (485±24 mg/L). Investigated sulfate-reducing bacteria were corrosive-relevant. The most corrosive bacteria were isolated from soils near the surface of the gas main pipeline. Under the action of Desulfotomaculum sp. K1/3 and Desulfovibrio sp. K2/3 corrosion rates of the steel coupons were 0.1±0.004 and 0.09±0.0031 g/m 2 ×hour, respectively at 5 exposition day. Under the action of Desulfotomaculum sp. ТС3 and Desul­fomicrobium sp . ТС4 strains isolated from heating systems corrosion rates were 0.086±0.0035 and 0.07±0.0021 g/m 2 ×hour, respectively. Collection strain Desulfovibrio vulgaris 644 had the smallest corrosion rate (0.047±0.0023 g/m 2 ×hour) among investigated bacteria from technogenic ecotopes. Corrosion rate is significantly increased to 0.081±0.0036 g/m 2 ×hour during the exposition period. Correlation was noted between hydrogen sulfide production and corrosion activity of investigated sulfate-redu­cing bacterial strains. Keywords: sulfate-reducing bacteria, hydrogen sulfide, microbial corrosion, corrosive aggressiveness.

EFFECT OF EXOGENOUS PROLINE IN TWO SUGARCANE GENOTYPES GROWN in vitro UNDER SALT STRESS

Sugarcane production is influenced by various abiotic stresses including salt stress. Salinity can induce oxidative stress, which in turn damages biomolecules and cellular structures. However, such damage can be avoided or minimized by the enzymatic and non-enzymatic defense systems of plants. The aim of the study was to determine the effect of exogenous proline on Na + and K + content and on the activity of catalase, ascorbate peroxidase and peroxidase in two sugarcane genotypes (RB931011 and RB872552) grown in vitro under salt stress. The plants were grown for 20 days with or without 100 mM NaCl and exposed to 20 mM proline for varying period of time. The data were subjected to ANOVA factorial (two genotypes and five treatments), and the mean values were compared by Tukey test at a 5% probability. Under salinity stress, both genotypes exhibited membrane integrity reduction, reduced total soluble protein content and unaltered or increased endogenous proline content. Exogenous proline reduced Na + accumulation in a manner proportional to the exposition period at the amino acid. In both genotypes, antioxidant enzymes activity increased with the addition of NaCl. In conclusion, RB931011 genotype showed higher proline accumulation and increased in activity of the antioxidant enzymes, indicating better salt stress tolerance than in RB872552 genotype.

Poumon de puisatier au Mali pendant la décennie 2001–2010

The well-digger is a craftsman who hollows wells often manually; this trade can be source of inhalation of the particles of silica. The whole of the radio clinical signs linked to this profession is known under the term "Well-digger's lung". The goal was to study the radio clinical aspects and progression in black African's pulmonological environment. Retrospective and descriptive study concerning the respiratory involvement of well-diggers in the Pulmonology service of the Teaching Hospital of Bamako, from January 2001 to December 2010. The admission registers were used as data verification support. Among 4158 admissions for lung affection, we have collected 39 cases of well-digger's lung (0.9%), all young male adults. The average of exposition period was 13 ± 9 years, correlated to the patient's age (p<0.001). The principal reason of consultation was dyspnea (94.8%). The complications were frequent (cardiac, infectious, pleural). The radiological pictures were made of bilateral big opacities associated with small opacities. The evolution was unfavorable in the majority of the cases. The well-digger's lung is a young adult pneumoconiosis linked to the inhalation of the particles of silica during the trade (profession) of well-digger that complicates frequently in chronic respiratory insufficiency.

Concentration of polycyclic aromatic hydrocarbons in Hypogymnia Physodes (L.)Nyl. thalli and changes to morphological structure / Kumulacja wielopierścieniowych węglowodorów aromatycznych w plechach Hypogymnia physodes (L.)Nyl. i zmiany w ich budowie morfologicznej

Abstract Apart from widely known anthropogenic pollutants as SO2, NOx, CO2, CO, there are another dangerous substances emitted to the air named polycyclic aromatic hydrocarbons (PAH). In the air they occur in a form of vapours and aerosols deposited on dust particles of 10 μm (PM 10) and 2.5 μm (PM 2.5) in diameter. In cities, the air polluted by gases and atmospheric particulate was analysed using special automatic or semi-automatic equipment or analytic procedures. That is why a powerful development of bioanalytical techniques based on using organisms as bioindicators is observed in recent years. The lichens are the most frequently used organisms in bioindication. The purpose of this research is to evaluate air pollution by PAHs in urban agglomeration with the use of Hypogymnia physodes (L.)Nyl. The research was performed in two hundred thousand occupants in south-east Poland in 2004-2007. The lichens placed on tree branches of 30 cm on 4 crossroads, and the 3 branches were put in each research point. Before starting the exposition, the “O” sample had been collected that had been stored in a closed container before chemical analysis. The exposition period lasted for 3 months. Then PAHs were determined in collected lichens. The analysis was performed with high performance liquid chromatography (HPLC), LiChrosper (TM) column 100 RP - 18, UV detector; λ = 254 nm. The concentration was expressed in mg/kg of dry mass that is after deducting PAH value determined in “O” sample. The analysis of obtained results showed diverse concentration of the pollution in the analysed crossroads depending on the road traffic density and season. PAH concentrations were determined from 0.61 mg·kg-1 d.m. in the 1st quarter of 2004 to 2.56 mg·kg-1 d.m. in the 1st quarter of 2006, and from 0.48 mg·kg-1 d.m. in the 4th quarter of 2004 to 2.22 mg·kg-1 d.m. in the 4th quarter of 2006. Meteorological conditions influence the concentration of PAHs in lichens. The atmospheric precipitation contributed to the decrease of PAHs concentration in the air by scavenging the pollution with atmospheric particulate. The regression line amounted to y = 1.91759 - 0.00674 · x, at the confidence interval equal to p = 0.0308. A relation between the PAH concentration and air relative humidity turned out to be the most essential correlation. This relation indicates that the concentration of PAHs in the lichens increases with an increase of humidity. The line regression amounted to y = -1.04196 + 0.02897 · x, at the confidence interval equal to p = 0.0505.

UV-B radiation effects on terrestrial plants – A perspective

Both terrestrial and aquatic plants, the primary producers supporting life on earth, can be threatened by global climate change and particularly by UV-B radiation due to the depletion of the ozone layer in both Poles. The injurious effects of UV-B have been assessed mainly through in vitro studies and vary greatly according the dose received, the exposition period and the sensitivity of the species. Adaptive responses can include for example, synthesis of new compounds, increases of UV-B absorbing compounds or anti-oxidant enzymes. Morphological consequences are also documented such as reduced growth and thickening of leaves and cuticule. The main response of UV-B irradiation in indoor experiments is the formation of UV-B absorbing compounds such as phenolic compounds and flavonoids which function as protective screens, although in the natural habitat plants living at higher altitudes and latitudes are tolerant to UV-B due to the natural selection. The main conclusion derived from studies with terrestrial plants is that photosynthesis is not significantly affected by changes in UV-B radiation when plants grow under natural conditions. Moreover, due to the successful implementation of the Montreal Protocol the increase of UV-B radiation in most populated regions of the world (i.e., outside the regions affected by the Antarctic ozone hole) has been modest.

Schistosoma mansoni: In vitro schistosomicidal activity of essential oil of Baccharis trimera (less) DC

Schistosomiasis is a chronic parasitic disease caused by the trematode species Schistosoma mansoni. Chemotherapy is the only immediate recourse to minimize the prevalence and incidence of this disease worldwide. At present, praziquantel (PZQ) is the drug of choice for the treatment of all forms of schistosomiasis. However, dependence on a single drug is concern because some strains can become resistant. In this context, medicinal plants become potential candidates as sources of new drug prototypes. This study provides findings on the schistosomicidal activity of the essential oil of Baccharis trimera in in vitro assays. During the assays parameters such as motility of adult worms, oviposition, morphological changes on the tegument and especially the mortality rate of adult worms of the BH strain were evaluated. The assays, which were carried out with four concentrations – 24, 48, 91 and 130μg/mL – of the essential oil, have shown a promising activity regarding the parameters under study. It was possible to notice a significant decline in the motility of the worms and a mortality rate of 100% 30h after they had been exposed to the essential oil in the concentration of 130μg/mL. Male worms were more susceptible, producing a dose-response effect within a smaller exposition period than female worms. In what refers to morphological changes, the essential oil of B. trimera induced a peeling on the tegument surface, as well as the destruction of tubercles and spines, which resulted in smooth areas on the body surface. The essential oil also caused tegument destruction in female worms, in addition to destruction of the oral and acetabular suckers. It is the first time that the schistosomicidal activity has been reported for essential oil of B. trimera (less) DC.

Thermal and mechanical evaluation of the stability of recycled poly(ethylene terephthalate) applied as sand control agent in petroleum wells

In petroleum wells, the granular sand control agents commonly employed are basically inorganic compounds, which are used in operations to prevent the production of sand, from unconsolidated sandstone formations, that contaminates the produced hydrocarbons. In this work the viability of applying recycled poly(ethylene terephthalate) (PETrec) as sand control agent, in an environment that simulated the conditions of the wells, was evaluated. Virgin PET (PETvir) was tested as a standard for comparison means. Pellets of each polymer (PETrec and PETvir) were confined into metallic cells filled with sea water or petroleum, under conditions observed in some sandstone formations that are normally subjected to sand control, in Campos Basin (Rio de Janeiro, Brazil). The cells systems were submitted to a controlled temperature of 70 °C and pressure of 24.1 MPa, and rolled during the experiment period. The total exposure time was approximately six months (172 days), with scheduled sampling periods. Thermal, mechanical and granulometric properties of the pellets before and after the exposition were evaluated. The samples were characterized by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TG). Mechanical experiments were performed, in order to determine the grain pack permeability, by the end of the exposition period, according to API RP 58 and API RP 61 standard methods. Particle size of the grains, before and after the exposure process, was compared. Test results showed that PETrec and PETvir samples did not present significant physical changes or evidences of degradation, nor in water neither in petrol, suggesting that the use of recycled PET as sand control agent seemed to be viable within the experiment conditions.

Efficacy of a single treatment of head lice with a neem seed extract: an in vivo and in vitro study on nits and motile stages

An anti-louse shampoo (Licener®) based on a neem seed extract was tested in vivo and in vitro on its efficacy to eliminate head louse infestation by a single treatment. The hair of 12 children being selected from a larger group due to their intense infestation with head lice were incubated for 10min with the neem seed extract-containing shampoo. It was found that after this short exposition period, none of the lice had survived, when being observed for 22h. In all cases, more than 50-70 dead lice had been combed down from each head after the shampoo had been washed out with normal tap water. A second group of eight children had been treated for 20min with identical results. Intense combing of the volunteers 7days after the treatment did not result in the finding of any motile louse neither in the 10-min treated group nor in the group the hair of which had been treated for 20min. Other living head lice were in vitro incubated within the undiluted product (being placed inside little baskets the floor of which consisted of a fine net of gauze). It was seen that a total submersion for only 3min prior to washing 3× for 2min with tap water was sufficient to kill all motile stages (larvae and adults). The incubation of nits at 30°C into the undiluted product for 3, 10, and 20min did not show differences. In all cases, there was no eyespot development or hatching larvae within 7-10days of observation. This and the fact that the hair of treated children (even in the short-time treated group of only 10min) did not reveal freshly hatched larval stages of lice indicate that there is an ovicidal activity of the product, too.

Variations in the composition of the ferromanganese concretions of the Kara Sea

It has been found when studying the distribution of 57 elements in flattened, pellet-shaped, and pipelike iron-manganese concretions of the Kara Sea, that the F2O3 and MnO2 contents in them are 52.5 and 5.30%; 18.3 and 24.2%; and 13.0 and 0.44%, respectively. The pellet-shaped concretions are enriched with nonferrous metals and microelements (especially with arsenic, cobalt, molybdenum, and animony) to the highest degree relative to the sediments, the flattened concretions are enriched to a lesser degree, and the pipelike ones are enriched to the least degree. The relative enrichment with the medium elements and a negative cerium anomaly are observed in the distribution of the rare-earth elements, which is also revealed in the host sediments to a lesser degree. The low content of ore and rare elements in the iron-manganese concretions of the Kara Sea relative to oceanic concretions is related mostly to the high sedimentation rates and short exposition period of the concretions on the sea bottom.

Practical consequences for the use of a personal dosemeter for fast neutrons at high-energy accelerators based on PADC detectors exposed up to one year

Abstract Since 1998, Paul Scherrer Institut has employed the routine use of a personal neutron dosimetry system based on chemically etched PADC (poly allyl diglycol carbonate) detectors and automatic track counting. In 2004, a new concept for individual monitoring at high-energy accelerators was implemented. In this concept the photon dosemeter of a combined photon/neutron dosemeter is evaluated monthly. The neutron dosemeter is only evaluated if the personal photon dose exceeds 2 mSv, or if the exposition period of the neutron dosemeter exceeds one year. Significant consequences for the evaluation of the neutron dosemeter in the dosimetry service were evidenced in the new concept. The wearing period of the neutron dosemeter can range from 1 to 12 months, potentially longer. Therefore, the long-term behavior of background track density and variation of response to Am–Be within 17 months was studied. The effects of “fading” and “aging” that influence the response of PADC detectors are determined. The application of an algorithm for neutron dose calculation takes into account long-term behavior and is described. Furthermore, repeated field calibrations were performed at the CERN-EU high-energy reference field (CERF) facility.

Regeneração in vitro de melão, cv. 'Gaúcho'

O objetivo do presente trabalho foi otimizar um protocolo de regeneração de explantes cotiledonares de melão, cultivar 'Gaúcho', avaliando a composição de meios de germinação e o tempo de permanência dos explantes nesses meios. Para isso, as sementes foram germinadas em meio MS semi-sólido contendo BAP ou ANA e sem esses reguladores de crescimento. As sementes permaneceram nesses meios por um, dois, três e quatro dias, sendo então seus cotilédones inoculados em meio MS contendo diferentes concentrações de BAP (0,5; 0,9; 1,5 e 2,0mg L-1). As maiores taxas de regeneração ocorreram nos cotilédones oriundos de sementes mantidas durante um e dois dias nos meios contendo 0,5 e 0,9mg L-1 de BAP. O aumento da permanência dos explantes nos meios de germinação e as elevadas concentrações de BAP nos meios de regeneração diminuíram a capacidade organogênica dos explantes e incrementaram a formação de calos.

Doping and Urologic Tumors

Several substances such as growth hormone (GH), erythropoietin (Epo), and anabolic steroids (AS) are improperly utilized to increase the performance of athletes. Evaluating the potential cancer risk associated with doping agents is difficult since these drugs are often used at very high doses and in combination with other licit or illicit drugs. The GH, via its mediator, the insulin-like growth factor 1 (IGF-1), is involved in the development and progression of cancer. Animal studies suggested that high levels of GH/IGF-1 increase progression of androgen-independent prostate cancer. Clinical data regarding prostate cancer are mostly based on epidemiological studies or indirect data such as IGF-1 high levels in patients with prostate cancer. Even if experimental studies showed a correlation between Epo and cancer, no clinical data are currently available on cancer development related to Epo as a doping agent. Androgens are involved in prostate carcinogenesis modulating genes that regulate cell proliferation, apoptosis and angiogenesis. Most information on AS is anecdotal (case reports on prostate, kidney and testicular cancers). Prospective epidemiologic studies failed to support the hypothesis that circulating androgens are positively associated with prostate cancer risk. Currently, clinical and epidemiological studies supporting association between doping and urological neoplasias are not available. Nowadays, exposure to doping agents starts more prematurely with a consequent longer exposition period; drugs are often used at very high doses and in combination with other licit or illicit drugs. Due to all these elements it is impossible to predict all the side effects, including cancer; more detailed studies are therefore necessary.

Long-term stability study on a Perna perna mussel candidate reference material

The long-term stability study, one of the steps in the characterization of new reference materials, is performed on freeze-dried biological reference materials to verify if they may be stored at room temperature without modification of the property values of interest. In this study, instrumental neutron activation analysis was used in a 12-month long isochronous long-term stability study performed on a Perna perna mussel candidate reference material. No trend in the results was observed in respect to measurement order and exposition period to room temperature. The assessment of the analysis of variance test as well as the normalized results to the control temperature showed no systematic changes in the mass fractions of Ag, As, Br, Co, Cr, Cs, Fe, Eu, La, Na, Rb, Sc, Se, Th and Zn during the test period. The result showed that the candidate reference material may be stored at room temperature without significant changes in composition for the determined elements.

Efficacy of a grapefruit extract on head lice: a clinical trial

Twenty children aging 2-9 years old--four boys with short hair and 16 girls with long hair--were included in a clinical test on the efficacy of a product against head lice (Pediculus humanus capitis). Their hair were exposed to Licatack, which is a recently developed new anti-louse medicinal product containing extracts of grapefruits besides high quality shampoo components. Prior to this field trial, the product Licatack was tested dermatologically to be skin safe receiving the grade "very good". The children's mothers combed the kids prior to the start of the test in order to confirm that they were all lice-infested. The obtained lice were used for in vitro tests. All children were heavily infested. After combing and preservation of the living lice, the hair was wet with tap water. Then, 50 ml of the Licatack shampoo was placed onto the top of each child's head. Then, the mothers distributed the rather fluid product all over the hair thoroughly from their base at the skin until the free end. During this process, a type of massage, the product became foamy and it was easily recognized where the product covered the hair, thus, avoiding untreated spots. The hair of half of the treated children were washed with tap water after 10 min of exposition; while in the other half of the children, the exposition period was prolonged to 20 min before washing. When combing the kids with a metal louse comb after the washing, the lice were found immobile and they did not recover during the following observation period of 4 h. Only two lice from the group with an exposition time of only 10 min showed some slight leg movements after they had been combed off, but they died within the next 2 h. Thus, this new anti-louse medicinal product has a very quick and efficient activity besides its advantages of being non-inflammable, skin safe, and nice smelling. None of the kids claimed any burning at the skin or other side effects, although the skin showed, prior to treatment, lots of scars due to louse bites. The dead lice always appeared considerably shrunken due to drying. The second treatment after 10 days revealed a few dead larval stages since, apparently, some larvae (apparently treated at an early stage of development when treated) had hatched from the extremely numerous nits in the period between first and second treatment. Experiments with cutoff nits, however, showed that the product also kills larval stages inside nits.

Teste de envelhecimento acelerado em sementes de aveia preta

Objetivou-se com este trabalho, estudar o teste de envelhecimento acelerado tradicional (com água), em sementes de aveia preta com e sem tratamento fungicida, e o envelhecimento acelerado com solução saturada de cloreto de sódio (NaCl), visando identificar o período de exposição e a temperatura para a classificação dos níveis de vigor de lotes dessas sementes. Foram utilizados cinco lotes de sementes, nos quais foram realizados testes para a caracterização da qualidade inicial de lotes (germinação, emergência de plântulas, condutividade elétrica, o comprimento de plântulas normais e massa de 1000 sementes), e estudado o envelhecimento acelerado tradicional (com água), com e sem tratamento fungicida, e o envelhecimento acelerado com solução saturada de sal (NaCl) por períodos de 24, 48, 72, 96 e 120 horas de condicionamento às temperaturas de 40, 43 e 45ºC. O teste de envelhecimento acelerado é adequado para estimar o vigor de sementes de aveia preta pelo procedimento tradicional (com e sem tratamento fungicida) ou com solução saturada de sal, ambos a temperatura de 40ºC por 24 horas.

Avaliação físico-mecânica de colmos de bambu tratados

O bambu é um material renovável e de baixo custo, encontrado em abundância em regiões tropicais e subtropicais; no entanto, a maior parte das espécies de bambu é altamente suscetível ao ataque de fungos e insetos. Basicamente, pode-se aumentar a durabilidade dos colmos de bambu; de duas maneiras: por procedimentos culturais (naturais) e pelo tratamento dos colmos com produtos químicos. Neste trabalho, testou-se a eficiência da aplicação do Método de Boucherie Modificado, comparando-se o aumento na durabilidade das amostras tratadas (taliscas de bambu) com amostras não tratadas ou testemunhas. Para tal, avaliaram-se os efeitos de algumas variáveis, tais como: posição da amostra no colmo, tipos de preservativo e sua concentração, duração do tratamento e tempo de exposição das taliscas em dois ambientes (protegido e exposto) e se realizaram ensaios não destrutivos - END (visual, pesagem das amostras e de ultra-som) e destrutivo (flexão estática). Verificou-se a ineficiência do uso de soluções com baixa concentração, principalmente quando elas foram combinadas com tratamentos de curta duração. Os ensaios de ultra-som e de flexão estática foram suficientemente sensíveis para detectar a melhor combinação do efeito dos parâmetros avaliados.

Photolytic degradation of the insecticide thiamethoxam in aqueous medium monitored by direct infusion electrospray ionization mass spectrometry

Photodegradation of the insecticide thiamethoxam (1), 3-[(2-chloro-5-thiazolyl)methyl]tetrahydro-5-methyl-N-nitro-4H-1,3,5-oxadiazin-4-imine, in an aqueous medium was monitored by electrospray ionization mass spectrometry in the positive ion mode, ESI(+)-MS. An aqueous solution of (1) was incessantly exposed to a UV radiation source and aliquots were taken after reaction times of 1, 2, 3, and 4 h. Analysis by GC/NCI-MS revealed that (1) was continuously degraded under these experimental conditions. However, the total organic carbon (TOC) content remained practically constant during the exposition period, thereby indicating that 1 was not mineralized but continuously converted into other compounds. ESI(+)-MS monitoring revealed that whereas the intensity of the ions of m/z 292/294 ([1 + H](+)) constantly decreased, there was the emergence of other ions of m/z 247/249, 197, 168, and 116 whose intensities simultaneously increased. Their structures were proposed on the basis of: (1) the data of their ESI(+)-MS/MS; (2) their high resolution m/z values; and (3) a plausible reactivity of the thiamethoxam molecule exposed to UV radiation in aqueous solution. Finally, these data allowed us to suggest a reaction route for the photodegradation of 1 in an aqueous medium.

Riboflavin production from mutants ofAshbya gossypii utilising orange rind as a substrate

The use of agroindustrial wastes such as orange rind as an alternative in the production of riboflavin was evaluated in this study withAshbya gossypii mutants.Ashbya gossypii mutants were obtained using 300 μg/mL of MNNG after an exposition period of 90 min with 2.3% of survival rate. A total of 11 mutant high yield strains of riboflavin were selected. Of these mutants, the most productive in YM medium were ASHLVII, ASHLX, ASHLXI and ASHLXV. Three additional different mutants were shown to be unsusceptible to inhibition by itaconate in the medium. When we used orange rind at 0.3% in YM medium without malt extract, the rate of riboflavin production was enhanced in the mutant strains producing 223 mg/L of this vitamin, an increase of 184% in the ASHLXI and ASHLXV mutants, as compared with the wild strain.

O teste de frio sem solo em sementes de abóbora

Este trabalho teve como objetivo determinar o período de exposição à baixa temperatura no teste de frio sem solo, para avaliação de diferentes potenciais fisiológicos em lotes de sementes de abóbora. Foram avaliados seis lotes de sementes de abóbora cultivar "Menina Brasileira" (Cucurbita moschata Duch.) produzidas na safra 2003/2004. As sementes foram submetidas a diferentes períodos (três, cinco, sete e nove dias) de exposição à baixa temperatura para condução do teste de frio sem solo, a uma temperatura constante de 10°C. Utilizou-se o delineamento inteiramente casualizado, em que os tratamentos constituíram um fatorial 6x4 (seis lotes e quatro períodos de exposição), com quatro repetições de 50 sementes. As médias foram comparadas pelo teste de Tukey em nível de 5% de probabilidade de erro. Realizou-se também o teste de correlação simples de Pearson .Os resultados permitiram concluir que o período de três dias de exposição à baixa temperatura foi o mais indicado para a condução do teste de frio sem solo em sementes de abóbora.