Hours Of Imbibition Research Articles

Metabolism of excised embryos of Lupinus luteus L. VI. An electrophoretic analysis of some dehydrogenases in cultured embryos as compared with the normal seedling axes

The electrophoretic patterns (disc electrophoresis) of the studied dehydrogenases: glucose-6-phosphate - (A), malate - (B), glutamate - (C), alcohol - (D) and lactate dehydrogenase (E), in the axial organs of isolated <i>Lupinus luteus</i> embryos and seedlings cultivated over 12 days are characterized by great similarities. With time, after the third day of cultivation the patterns begin to become less deyeloped. Analyses performed during the first 10 hours of imbibition of seed parts indicate that the maximal development of isozyme patterns occurs during the third hour after which the patterns become poorer. The most uniform type of pattern. and the lowest number of isozymes was shown by glutamate dehydrogenase, the richest pattern was shown by malate dehydrogenase. No band common for a 11 the 27 experimental elements was found.

Germinação de sementes de Melanoxylon brauna schott em diferentes temperaturas

Os objetivos deste trabalho foram investigar o efeito da temperatura sobre a germinação de sementes de Melanoxylon brauna e identificar as temperaturas cardinais de germinação, bem como avaliar a eficiência do teste de condutividade elétrica para determinação das temperaturas cardinais. Para tanto, foram realizados três ensaios. No primeiro, foi feita a determinação das curvas de embebição, em cada temperatura (5, 10, 15, 20, 25, 30, 35, 40 e 45 ºC); as sementes foram pesadas a cada 2 h, por um período de 12 h e após a cada 12 h até a protrusão radicular de 50% das sementes, ou até 120 h quando na ausência de germinação. No segundo ensaio, para identificar as temperaturas cardinais, as sementes foram mantidas sob cada temperatura, por 10 dias, em câmara tipo BOD, sob luz constante. No terceiro ensaio, foi realizado um teste de condutividade elétrica com as sementes incubadas por períodos de 24, 48 e 72 h de embebição em cada uma das temperaturas e, em seguida, colocadas em erlenmeyers com 75 mL de água deionizada a 25 ºC, por 24 h, para posterior leitura da condutividade elétrica. É mais criterioso recomendar faixas de temperaturas para germinação do que temperaturas pontuais. As temperaturas cardinais (teóricas) para a característica porcentagem de germinação são: 12,3 ºC - mínima, 30,0 ºC - ótima (teórica) e 42,7 ºC - máxima. As faixas de temperatura considerando todas as variáveis investigadas são: 12,1-12,6 ºC (mínima); 30,0-35,8 ºC (ótima); e 42,4-43,0 ºC (máxima). A espécie apresenta grande amplitude de germinação com relação à temperatura, sendo verificada a germinação na faixa de 12,0 a 42,0 ºC. O teste de condutividade elétrica foi eficiente para avaliar o efeito da temperatura sobre as sementes e, nesse teste, a temperatura ótima é de 27,0 ºC..

Condução do teste de condutividade elétrica utilizando partes de sementes de feijão

The aim of this work was identify the best conditions for bulk and individual electrical conductivity evaluation using bean seed parts at the less time for imbibition as possible. Beans seeds cultivar IAPAR 81 were used in this work, and represented by four lots. Physiological potential was evaluated by germination standard test, first count germination, seedling vigour classification, speed radicle protrusion, and field seedling emergence. Electrical conductivity test was done by bulk and individual procedures, with whole seeds, cotyledons and embryonic axis at different immersion periods. The bulk electrical conductivity test is able to identify vigour differences in bean seed lots after two hours of imbibition using exclusively cotyledons or with whole seeds after five hours of imbibition, and both methodologies are able to classify bean seed lots by vigor levels.

Caracterization of seed germination of Zephyranthes sylvatica (Mart.) Baker (Amarilidacea)

Zephyranthes sylvatica is a beautiful lily, endemic from the Brazilian Caatinga. Although it has a great ornamental potential, little is known about this species, especially regarding its seeds germination process. Aiming to characterize the germination of Z. sylvatica seeds, we studied its imbibition curve, optimum temperature and substrate for germination and seedling emergence, osmotic and salt stress tolerance, as well as the tolerance to frosting/ defrosting, which indicates long term cryostorage potential. The germination of Z. sylvatica presents a triphasic model of imbibition, in which the primary root protrusion occurs after 72 hours of imbibition. The ideal conditions for evaluating seed germination of Z. sylvatica is 25 ºC, in paper rolls. These seeds are highly tolerant to osmotic stress, but not to salt stress. Z. sylvatica seeds can be cryopreservated without loss of germination and seed vigor.

Loss of desiccation tolerance in Copaifera langsdorffii Desf. seeds during germination.

This study evaluated the loss of desiccation tolerance in C. langsdorffii seeds during the germination process. Seeds were imbibed for 24, 48, 72, 96, 120 and 144 hours and dried to the initial moisture content, kept in this state for 3 days after which they were submitted to pre-humidification and rehydration. Ultraestructural evaluations were done aiming to observe the cell damage caused by the dry process. Desiccation tolerance was evaluated in terms of the percentage of normal seedlings. Seeds not submitted to the drying process presented 61% of normal seedlings, and after 24 hours of imbibition, followed by drying, the seeds presented the same percentage of survival. However, after 48 hours of imbibition, seeds started to lose the desiccation tolerance. There was twenty six percent of normal seedlings formed from seeds imbibed for 96 hours and later dried and rehydrated. Only 5% of seeds imbibed for 144 hours, dried and rehydrated formed normal seedlings. At 144 hours of imbibition followed the dry process, there was damage into the cell structure, indicating that the seeds were unable to keep the cell structure during the drying process. Copaifera langsdorffii seeds loses the desiccation tolerance at the start of Phase 2 of imbibition.

Russian

Damage of seeds which leads to destruction of the crystal lattice and the phase transition of polymers is formed under the pulse pressure (PP) treatment. Biopolymers such as starch compressed under specific conditions can be changed from crystalline to a glassy state; this transition is known to extend the life of seeds. The aging of seeds is involved in the enzymatic glycosylation of proteins and nucleic acids. Reducing sugars which have been produced in seeds by non-enzymatic hydrolysis enter into reaction of glycosylation with proteins and amino acids actively. The authors studied the water absorption by seeds of buckwheat (Fagopyrum esculentum Moench., cultivar Saulyk) treated by PP. The values of PP which were used to treat had an influence on water absorption during the first hours of imbibition. When water content was 60%, hydrolysis of reserve substances could begin, so water potential was created by osmotically active molecules. Gibbs energy calculation by method of groups' contribution indicated the reduction in probability of starch hydrolysis in plant seeds during transition from the crystalline to the glassy state. Keywords: pulse pressure; biopolymer; destruction; starch; buckwheat; hydrolysis. Введение. В качестве фактора, действующего на растения, было выбрано импульсное давление (ИД), создаваемое прохождением ударной волны. ИД в интервале 3-35 МПа способствует стимулированию физиологических процессов в семенах и растениях, ведущих к

Regulation of ribosome biogenesis in maize embryonic axes during germination

Ribosome biogenesis is a pre-requisite for cell growth and proliferation; it is however, a highly regulated process that consumes a great quantity of energy. It requires the coordinated production of rRNA, ribosomal proteins and non-ribosomal factors which participate in the processing and mobilization of the new ribosomes. Ribosome biogenesis has been studied in yeast and animals; however, there is little information about this process in plants. The objective of the present work was to study ribosome biogenesis in maize seeds during germination, a stage characterized for its fast growth, and the effect of insulin in this process. Insulin has been reported to accelerate germination and to induce seedling growth. It was observed that among the first events reactivated just after 3 h of imbibition are the rDNA transcription and the pre-rRNA processing and that insulin stimulates both of them (40-230%). The transcript of nucleolin, a protein which regulates rDNA transcription and pre-rRNA processing, is among the messages stored in quiescent dry seeds and it is mobilized into the polysomal fraction during the first hours of imbibition (6 h). In contrast, de novo ribosomal protein synthesis was low during the first hours of imbibition (3 and 6 h) increasing by 60 times in later stages (24 h). Insulin increased this synthesis (75%) at 24 h of imbibition; however, not all ribosomal proteins were similarly regulated. In this regard, an increase in RPS6 and RPL7 protein levels was observed, whereas RPL3 protein levels did not change even though its transcription was induced. Results show that ribosome biogenesis in the first stages of imbibition is carried out with newly synthesized rRNA and ribosomal proteins translated from stored mRNA.

Physiological potential of eggplant seeds

The use and efficiency of vigor tests depend on the plant species and the development and, or adjustment of methodology, to obtain efficient procedures for evaluating seed physiological potential. The objective of this study was to compare different methods for evaluating the physiological potential of eggplant seeds (Solanum melongena L). Six seed lots of the "Comprida Roxa" cultivar were submitted to the following tests: germination, first count germination, seedling emergence, controlled deterioration (18, 21 and 24% for 24 and 48 hours at 45 °C), accelerated ageing (AA) and saturated salt accelerated ageing (both at 41 and 45 °C for 24, 48 and 72 hours) and electrical conductivity (25 seeds, 50 and 75 mL of water for 1, 2, 4, 8, 12, 16 and 24 hours of imbibition at 25 °C). The first count test provided preliminary information on seed germination and the other tests, in general, gave similar results for seedling emergence. It was concluded that the physiological potential of eggplant seeds can be evaluated using AA for 48 h/41 °C and controlled deterioration at 24% moisture content/ 24 h/45 °C. The best conditions for the electrical conductivity test on eggplant seed are using 25 seeds in 50mL of water for four hours at 25 ºC.

A seed respiration-based index of cold-sensitivity during imbibition in four macrothermal species

A research was carried out to evaluate the influence of temperature on seed respiration response of maize, cotton, grain sorghum and sunflower during imbibition, and to define reliable indices for a fast evaluation of cold-sensitivity at germination level in plants. The seed respiration activity was measured during seed imbibition at 25 °C (optimal) and 15 °C (suboptimal) constant temperatures, using a homemade respiration chamber adapted to an infrared gas analyzer. At 15 °C, sunflower and sorghum maintained high levels of seed germination (≥90 %), whilst this last dropped in cotton (36.7 %) and maize (27.8 %). With respect to this, cotton and maize seem to be cold sensitive during germination. Instantaneous seed respiration during imbibition versus temperature or thermal time could not be used as a good indicator for cold tolerance, since the levels of CO2 recorded at 15 °C in cotton (higher than the other species) and maize (similar to that of sorghum and sunflower) did not correspond to adequate seed germination. Differently, the rates (b coefficient of linear regressions) of accumulation of CO2 respired at optimal and suboptimal temperatures during the first hours of imbibition (up to approximately 24 h from the start of experiment), were significantly different in maize and cotton, whilst they did not differ in sorghum and sunflower. Therefore, the shift between slopes may represent a reliable index for seed cold-sensitivity assessment during early germination.

Methods for evaluating the physiological potential of scarlet eggplant (Solanum aethiopicum) seeds

The use and efficiency of vigour tests depend on the plant species and the development and / or adjustment of methodology to obtain efficient procedures for evaluating seed physiological potential. The objective of this study was to compare different methods for evaluating the physiological potential of scarlet eggplant seeds (Solanum aethiopicum Scarlet eggplant Group). Six seed lots of the “Morro Grande’ cultivar were submitted to the following tests: germination, first count germination, seedling emergence, controlled deterioration (18, 21 and 24% for 24 and 48 hours at 45°C), accelerated ageing (AA) and saturated salt accelerated ageing (SSAA; NaCl) both at 41 and 45°C for 24, 48 and 72 hours) and electrical conductivity (25 and 50 seeds; 25, 50 and 75 mL of deionised water for 1, 2, 4, 8, 12, 16 and 24 hours of imbibition at 25°C). With the exception of electrical conductivity, results from the first count test and for specific times / temperatures of the other tests, generally showed similar ranking of the lots as seen for seedling emergence. It was concluded that the physiological potential of scarlet eggplant seeds can be evaluated using AA and SSAA for 48 h / 41°C and controlled deterioration at 24% moisture content / 24 h / 45°C, thus classifying the seed lots into different vigour levels.

Automated system of seedling image analysis (SVIS) and electrical conductivity to assess sun hemp seed vigor

The development of new procedures for quickly obtaining accurate information on the physiological potential of seed lots is essential for developing quality control programs for the seed industry. In this study, the effectiveness of an automated system of seedling image analysis (Seed Vigor Imaging System - SVIS) in determining the physiological potential of sun hemp seeds and its relationship with electrical conductivity tests, were evaluated. SVIS evaluations were performed three and four days after sowing and data on the vigor index and the length and uniformity of seedling growth were collected. The electrical conductivity test was made on 50 seed replicates placed in containers with 75 mL of deionised water at 25 ºC and readings were taken after 1, 2, 4, 8 and 16 hours of imbibition. Electrical conductivity measurements at 4 or 8 hours and the use of the SVIS on 3-day old seedlings can effectively detect differences in vigor between different sun hemp seed lots.

A stress-associated protein containing A20/AN1 zing-finger domains expressed in Medicago truncatula seeds

MtSAP1 (Medicago truncatula stress-associated protein 1) was revealed as a down-regulated gene by suppressive subtractive hybridization between two mRNA populations of embryo axes harvested before and after radicle emergence. MtSAP1 is the first gene encoding a SAP with A20 and AN1 zinc-finger domains characterized in M. truncatula. MtSAP1 protein shares 54% and 62% homology with AtSAP7 (Arabidopsis thaliana) and OsiSAP8 (Oryza sativa) respectively, with in particular a strong homology in the A20 and AN1 conserved domains. MtSAP1 gene expression increased in the embryos during the acquisition of tolerance to desiccation, reached its maximum in dry seed and decreased dramatically during the first hours of imbibition. Abiotic stresses (cold and hypoxia), abscisic acid and desiccation treatments induced MtSAP1 gene expression and protein accumulation in embryo axis, while mild drought stress did not affect significantly its expression. This profile of expression along with the presence of anaerobic response elements and ABRE sequences in the upstream region of the gene is consistent with a role of MtSAP1 in the tolerance of low oxygen availability and desiccation during late stages of seed maturation. Silencing of MtSAP1 by RNA interference (RNAi) showed that the function of the encoded protein is required for adequate accumulation of storage globulin proteins, vicilin and legumin, and for the development of embryos able to achieve successful germination.

Avaliação da perda da tolerância à dessecação e da quantidade de dna nuclear em sementes de Peltophorum dubium (spreng.) taubert durante e após a germinação

O presente trabalho teve por objetivo a avaliação da perda da tolerância à dessecação (TD) em sementes de Peltophorum dubium durante e após a germinação. As sementes foram colocadas para germinar e, ao atingirem 1, 3 e 5 mm de raiz primária (68% de umidade), foram desidratadas em sílica gel, até atingirem o grau de umidade inicial (8%), sendo em seguida reidratadas e avaliadas quanto à sobrevivência (retomada do crescimento e formação de plântulas normais). Procedimento semelhante foi adotado para os ensaios realizados durante a embebição, onde foram amostradas 100 sementes divididas em quatro repetições de 25 para cada um dos seguintes tempos de embebição: 12, 24, 48, 60 e 72 horas. Em seguida, foram selecionados diferentes pontos de interesse (12, 48 e 60 horas de embebição e raízes primárias com 1 mm de comprimento) para determinação da quantidade de DNA nuclear, afim de analisar possível correlação entre início do ciclo celular e perda da TD. Com relação ao comportamento de sementes germinadas submetidas à secagem e reidratação, para os três comprimentos de raízes primárias amostradas, não houve sobrevivência. Foi observada queda progressiva na sobrevivência de sementes de Peltophorum dubium relacionada ao tempo de embebição, e posterior secagem e reidratação, sugerindo que a perda da TD desta espécie acontece nos estágios iniciais da germinação, antes da protrusão da radícula. Sementes embebidas por 12 h, 24 h, 48 h, 60 h, 72 h e aquelas germinadas, com 1 mm de comprimento radicular, apresentaram índices iguais a 98%, 93%, 83%, 35%, 17% e 0% de sobrevivência respectivamente. Os estudos relacionados ao conteúdo de DNA nuclear não demonstram correlação entre retomada do ciclo celular e perda da TD.

Transcriptional regulatory programs underlying barley germination and regulatory functions of Gibberellin and abscisic acid

BackgroundSeed germination is a complex multi-stage developmental process, and mainly accomplished through concerted activities of many gene products and biological pathways that are often subjected to strict developmental regulation. Gibberellins (GA) and abscisic acid (ABA) are two key phytohormones regulating seed germination and seedling growth. However, transcriptional regulatory networks underlying seed germination and its associated biological pathways are largely unknown.ResultsThe studies examined transcriptomes of barley representing six distinct and well characterized germination stages and revealed that the transcriptional regulatory program underlying barley germination was composed of early, late, and post-germination phases. Each phase was accompanied with transcriptional up-regulation of distinct biological pathways. Cell wall synthesis and regulatory components including transcription factors, signaling and post-translational modification components were specifically and transiently up-regulated in early germination phase while histone families and many metabolic pathways were up-regulated in late germination phase. Photosynthesis and seed reserve mobilization pathways were up-regulated in post-germination phase. However, stress related pathways and seed storage proteins were suppressed through the entire course of germination. A set of genes were transiently up-regulated within three hours of imbibition, and might play roles in initiating biological pathways involved in seed germination. However, highly abundant transcripts in dry barley and Arabidopsis seeds were significantly conserved. Comparison with transcriptomes of barley aleurone in response to GA and ABA identified three sets of germination responsive genes that were regulated coordinately by GA, antagonistically by ABA, and coordinately by GA but antagonistically by ABA. Major CHO metabolism, cell wall degradation and protein degradation pathways were up-regulated by both GA and seed germination. Those genes and metabolic pathways are likely to be important parts of transcriptional regulatory networks underlying GA and ABA regulation of seed germination and seedling growth.ConclusionsThe studies developed a model depicting transcriptional regulatory programs underlying barley germination and GA and ABA regulation of germination at gene, pathway and systems levels, and established a standard transcriptome reference for further integration with various -omics and biological data to illustrate biological networks underlying seed germination. The studies also generated a great amount of systems biological evidence for previously proposed hypotheses, and developed a number of new hypotheses on transcriptional regulation of seed germination for further experimental validation.

Teste de condutividade elétrica para sementes de feijão-mungo-verde

A utilização de sementes de boa qualidade é fundamental para o estabelecimento adequado de uma lavoura. Para uma análise mais precisa da qualidade de sementes, faz-se necessário complementar as informações fornecidas pelo teste de germinação com testes de vigor, possibilitando, assim, selecionar os melhores lotes para comercialização e semeadura. Dentre esses testes, destaca-se o de condutividade elétrica. Objetivou-se neste trabalho estabelecer uma metodologia adequada para o teste de condutividade elétrica em sementes de feijão-mungo-verde, considerando períodos de embebição e número de sementes. Foram utilizados seis lotes de sementes e o teste de condutividade elétrica foi realizado com as seguintes variações: 100, 75 e 50 sementes embebidas em 75 mL de água destilada a 25 °C, com leituras realizadas após 3, 6, 9, 12, e 15 horas de embebição. O teste de condutividade elétrica conduzido com quatro sub-amostras de 50 sementes embebidas em 75 mL de água destilada permite a separação dos lotes a partir de 3 horas de embebição, mostrando-se promissor na avaliação da qualidade das sementes de feijão-mungo-verde.

Seed Development and Germination in anArabidopsis thalianaLine Antisense to Glutathione Reductase 2

Desiccating and germinating seeds are particularly prone to oxidative stress. Glutathione (GSH) is one of the most abundant and ubiquitous antioxidants in plants. To better understand GSH's role in developing and germinating seeds, wildtype (WT) and a line of seed antisense for glutathione reductase 2 (anGR2), one of two glutathione reductase (GR) genes characterized in the genetic model plant Arabidopsis thaliana, were compared. GSH levels in maturing and germinating seeds were measured by high performance liquid chromatography (HPLC) and GR activity by native Polyacrylamide gel electrophoresis (PAGE). Natural and accelerated aging and germination at high temperature and under water stress were compared for WT and anGR2 seeds. Total GSH pools were two-fold less in anGR2 than in WT after three hours of imbibition. Under high temperature and osmotic stress, germination percentages were lower in anGR2, suggesting a specific relationship between GSH metabolism and stress defense mechanisms early in germinati...

Gene expression profiling identifies two regulatory genes controlling dormancy and ABA sensitivity in Arabidopsis seeds

Seed dormancy is a very important trait that maximizes the survival of seed in nature, the control of which can have important repercussions on the yield of many crop species. We have used gene expression profiling to identify genes that are involved in dormancy regulation in Arabidopsis thaliana. RNA was isolated from imbibed dormant (D) and after-ripened (AR) ecotype C24 seeds, and then screened by quantitative RT-PCR (qRT-PCR) for differentially expressed transcription factors (TFs) and other regulatory genes. Out of 2207 genes screened, we have identified 39 that were differentially expressed during the first few hours of imbibition. After analyzing T-DNA insertion mutants for 22 of these genes, two displayed altered dormancy compared with the wild type. These mutants are affected in genes that encode a RING finger and an HDZip protein. The first, named DESPIERTO, is involved in ABA sensitivity during seed development, regulates the expression of ABI3, and produces a complete loss of dormancy when mutated. The second, the HDZip (ATHB20), is expressed during seed germination in the micropylar endosperm and in the root cap, and increases ABA sensitivity and seed dormancy when mutated.

Light-Mediated Germination in Lettuce Seeds: Resurrection of a Classic Plant Physiology Lab Exercise

[ILLUSTRATION OMITTED] Most students are taught that plants use light for photosynthetic energy conversion. However, many students do not realize that plants also use light as a source of information that is translated into changing growth and development. In 1952, H.A. Borthwick and colleagues demonstrated that light controls germination in certain varieties of lettuce seeds. They found that red light was most effective at inducing germination of imbibed Grand Rapids var. lettuce seeds whereas far-red light inhibited germination. They also discovered that when lettuce seeds were given multiple exposures of one light color followed by the other, it was the last light treatment that determined the germination response. This classic study demonstrated that red and far-red light act as an and switch to regulate seed germination (Borthwick et al., 1952). These observations ultimately led to the isolation and characterization of the red/far-red light photoreceptors called phytochromes (meaning plant pigment). Based on this publication, Grand Rapids var. lettuce seeds were used in physiology laboratory teaching exercises to demonstrate phytochrome mediated red\far-red control of seed germination. However, during the past 20 years, most Grand Rapids derived varieties no longer require red light to induce germination. Though having uniform seed germination is ideal from an agricultural point of view, these lettuce breeding efforts have also led to the abandonment of this laboratory exercise demonstrating how light can regulate seed germination in plants. The purpose of this project is to identify which varieties derived from Grand Rapids lettuce still maintain a light-dependent germination response. With this information, this classic laboratory exercise can be resurrected. In addition, we present a new teaching tool that demonstrates the biological relevance of light-mediated seed germination and can be used in a lower budgeted class, such as in a public high school or college. * Germination Assay Count out 50 seeds for each light treatment. The treatments will be: dark, FR (far-red light), R (red light), and R/FR (red followed by far-red light). Place one or two sheets of Whatman (Maidstone, UK) #1 90 mm diameter filter paper (or some other absorbent paper) into four round, shallow petri dishes. Moisten the filter paper with distilled water so that they are damp, but not filled with standing water. In a darkroom lit by a green safety light (we use a 25A/TG, 25W, 120V, Transparent Green Party Bulb, A-19 Shape from General Electric, Fairfield, CT), place 50 seeds in the petri dish and label the dish with one of the light treatments. Wrap aluminum foil around each petri dish to create a light-tight seal (usually two layers) and let seeds imbibe (take up water) for at least one hour in the dark at room temperature. Be sure to re-label the plates after sealing with aluminum foil. After at least one hour of imbibition, place both the red light treatment dishes and the red to far-red light treatment dishes in a red light treatment chamber. Expose seeds to red light for approximately five minutes. For our experiments described here, we use red light emitting diodes (LEDs) in an E30-LED chamber (Percival Scientific, http://www.percival-scientific.com). We have also used cool white fluorescent bulbs filtered through a sheet of red (#2423) acrylic for our red light treatment. After the five-minute exposure, turn off the red light and, in the presence of the green safe light, cover the red light treatment dishes with enough aluminum foil to create a light-tight seal. Move the red to far-red light and the far-red light treatment dishes into a far-red light treatment chamber and expose for five minutes. For our experiments described here, we use far-red LEDs in an E30LED chamber (Percival Scientific, Perry, IA, http://www.percivalscientific. …

Envelhecimento acelerado para avaliação do potencial fisiológico de sementes de melão

O teste de envelhecimento acelerado tem potencial para ser utilizado no controle de qualidade de sementes de hortaliças. No entanto, há fatores que podem afetar os resultados, sendo necessários ajustes na metodologia para obtenção de resultados consistentes. Esta pesquisa foi conduzida com o objetivo principal de avaliar procedimentos para a condução do teste de envelhecimento acelerado para avaliação do potencial fisiológico de sementes de melão, incluindo o uso de solução saturada de NaCl em substituição à água. Sementes de dois híbridos de melão (Goldex e Vereda), cada um representados por cinco lotes, foram submetidos aos testes de germinação, primeira contagem de germinação, condutividade elétrica (16 e 24 horas de embebição), emergência de plântulas em casa de vegetação e envelhecimento acelerado. Neste, foram empregados dois procedimentos: tradicional (água) e solução saturada (40 g 100 mL-1) de NaCl, a 41ºC, por períodos de 24, 48 e 72 horas. Foi utilizado o delineamento inteiramente casualizado, com quatro repetições e análises isoladas para cada teste. Os testes de primeira contagem de germinação e emergência de plântulas foram eficientes na identificação dos lotes de sementes de qualidade inferior. Já o teste de condutividade elétrica não se constituiu em opção eficiente para avaliação do vigor das sementes. O teste de envelhecimento acelerado (procedimento tradicional e com solução salina saturada), utilizando o período de 72 horas, a 41ºC, mostra-se adequado para avaliação do potencial fisiológico de sementes de melão. Observou-se ainda que, em comparação com o uso de água, a utilização de solução salina no teste de envelhecimento acelerado inibiu sensivelmente o crescimento e desenvolvimento de fungos.

VIABILIDADE E VIGOR DE SEMENTES DE ACEROLA (Malpighia punicifolia) SUBMETIDAS À EMBEBIÇÃO SOB DIFERENTES TEMPERATURAS

Acerola is a fruit tree species highly rich in vitamin C, which has a great acceptance both in the domestic and foreign markets. However, its seeds present viability problems. This research aimed at studying the germination behavior of acerola seeds submitting them to different periods of imbibition in distilled water, under room temperature (24°C) and refrigerated (±10°C). The treatments consisted of 0, 24, 48 and 72 hours of imbibition. The following characteristics were evaluated: germination, first counting, and germination speed rate. The experimental design was completely randomized, following a 4x2 factorial scheme (imbibition periods x temperatures). The imbibition of acerola seeds in distilled water, between the periods of 38 and 48 hours, under room temperature, favored more viable and vigorous seedlings. KEY-WORDS: Acerola; germination; immersion in water; room temperature; refrigeration.