Due to increased use of treated seeds, studies are necessary in relation to the effects of the treatments and their possible consequences on seed quality. The aim of this study was to evaluate phytotoxicity according to when phytosanitary products are applied on soybean seeds and their effect on seed physiological quality and field performance. A completely randomized experimental design was used in a 9 × 2 factorial arrangement involving 9 seed treatments (fungicides and insecticides) and two application times (60 days before sowing and at the time of sowing in the field). Moisture content was determined and tests were performed to ascertain physiological quality (germination and germination under water restriction). Root and hypocotyl length, seedling length, and vigor and uniformity indices were evaluated with the assistance of Vigor-S®. In the field, the following determinations were made: plant height at 30 and 60 days after emergence, first pod height, number of pods per plant, number of seeds per pod, and yield. Early seed treatment in the soybean crop can affect initial development of the plants, but it does not affect yield. The phytotoxicity caused by the soybean seed treatment was observed in the root length characteristic.

The use of an appropriate method that accurately expresses physiological seed quality and minimizes possible phytotoxicity by chemical products in laboratory testing with soybean seeds is relevant. The objective of this work was to evaluate the influence and infer the method adequacy for the representative evaluation of physiological quality of soybean seeds treated with phytosanitary products. Two experiments were carried out in a completely randomized design, with trial 1 in a 9×5 factorial scheme involving nine seed treatments, including fungicides and insecticides, and solutions with five osmotic potentials (0, -0.25, -0.5, -0.75 and -1.0 MPa) for wetting a paper substrate in a germination experiment, with evaluation of the normal seedlings at five and eight days after sowing. The second experiment consisted of a 9×7 factorial, with nine seed treatments and seven methods for germination evaluation at 5 days (between paper - BP, between sand - BS, between paper with water restriction - BPWR, between paper with preconditioning - BPC, sand between paper - SBP and vermiculite between paper - VBP). Treatments with insecticides affect seedling germination and evaluation, with greater phytotoxicity in relation to fungicides. Methods with readily available water led to greater phytotoxicity than methods with low water availability. For soybean germination evaluation of seeds treated with phytosanitary products, the BPC, SBP and VBP methods were optimal.

Studies that evaluate the physiological and biochemical mechanisms of germination within forest species are needed in order to improve our understanding of such processes. Mercury and dithiothreitol are indicated as important tools in studies that assess the activity of aquaporins during imbibition and germination of seeds. To investigate the alterations caused by mercury in Plathymenia reticulata seeds, different doses of mercury were used in the presence and absence of dithiothreitol. Mercury had a dose-dependent effect on the seeds; in the most dilute solutions mercury partially inhibited the imbibition process, whereas in the most concentrated solutions it caused the death of the embryos. A delay in the hydration of the seeds may have caused decreased germination as a result of the reduced functionality of the aquaporins that were oxidized by mercury. In the presence of the reducing agent dithiothreitol, the activity of these proteins was restored and the germination process was re-established. These findings indicate the importance of aquaporins in the imbibition and germination stages of P. reticulata seeds, and they provide a better understanding of these important developmental events in plants.

No abstract

Germination does not guarantee plant establishment if there is no efficient and enough reserve mobilization from seeds to the initial seedling growth, mainly in adverse situations. Therefore, this study aimed to evaluate the mobilization of reserves in soybean seeds under water restriction. Four soybean seed lots previously stored for one year were used in the study. To simulate water stress, we used polyethylene glycol (PEG) solutions at concentrations of 0.0, -0.1, and -0.2 MPa. The number of normal, infected and abnormal seedlings were evaluated, along with the number of dead and hard seeds. The radicle, hypocotyl, and cotyledons were separated to determine the dry weight based on the total seed reserve available for mobilization. From this value, the seed reserve reduction, relative dry matter yield, seed reserve reduction rate, and reserve conversion efficiency into dry seedling weight were determined. The increase in water restriction elevates the reserve consumption during the germination process. Vigorous seeds are more efficient in mobilizing and converting grains reserve in dry seedling mass. In less vigorous seeds, mainly those on water restriction, the increase in reserve consumption does not result in conversion into dry seedling mass.

ABSTRACT:The use of tetrazolium test is important in the evaluation of seeds lot quality and it has been adopted for vigor and viability identification for several species. The interest on the production of oil radish is increasing since the seeds were considered a good source of oil for biofuel production. The development of the tetrazolium test methodology for seeds of this species can improve the seed quality control process, and additionally will provide information for the characterization of remaining seeds (dead or dormant) in the germination tests. To verify the ideal conditions to tetrazolium test was conducted two experiments. At the first, oil radish seeds cultivar CATI AL-1000, lots from 2001 and 2006 were submitted to imbibition between paper in water for 6 hours. After the longitudinal cut in the longest direction, the seeds were immersed in the tetrazolium solution at the concentrations of 0,075%, 0,5% and 1% at 25°C for 3h, 12h and 18h. In the second experiment, oil radish seeds cultivar CATI AL-1000 lot from 2005 and IPR 116 cultivar, lots from 2004 and 2005 were immersed in the concentrations of ,1%; 0,2%; 0,3% and 0,4% of tetrazolium solution for 12 hours at a 25°C, 30°C, 35°C and 40°C. At the first experiment was observed the necessity of test intermediate concentrations between 0,075% and 0,5%, since with 0,075% the seeds stained weakly and with 0,5% the test results, were overestimated. In the second experiment was observed that the 0,3% concentration at 30°C can be recommended for the utilization of tetrazolium test to evaluation of oil radish seeds viability.

Devido à baixa germinação de sementes de Bixa orellana L., há a necessidade de se testar diferentes técnicas que viabilizem sua reprodução, como o condicionamento fisiológico. O objetivo do presente trabalho foi caracterizar a germinação de dois lotes de sementes de urucum sob efeito do condicionamento fisiológico. Para isso, sementes de dois lotes (recém-colhido e armazenado) foram submetidas ao condicionamento fisiológico em solução aerada de: 1) água deionizada; 2) água catódica; 3) nitrato de potássio a 0,3%; 4) nitroprussiato de sódio a 100 µM; por 24 e 48h, e um tratamento adicional (controle) sem condicionamento. Após o teste de germinação, as  sementes que não germinaram foram submetidas ao teste de tetrazólio a 0,075% a 30 °C, no escuro, durante 24 h. O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial (4 x 2 + 1) com quatro repetições de 25 sementes por tratamento. Apesar da baixa germinação já relatada para a espécie, foi possível obter germinação sem nenhum tipo de pré-tratamento como quebra de dormência, mesmo em lote armazenado por 10 anos e com teor de água de 8%. Os agentes condicionantes não foram eficientes no aumento da germinação de sementes de urucum. São necessários novos trabalhos para classificação da espécie quanto ao seu armazenamento.

-The objective in this work was to investigate the effect of nitric oxide (NO) like protective agent in sesame seeds submitted to different osmotic potentials. The treatments, in total of eight, were water (control), water plus sodium nitroprusside (SNP) and the other treatments with PEG 6000 and PEG 6000 plus SNP: -0.1 MPa, -0.1MPa +200 µM of SNP, 0.2 MPa, -0.2 MPa +200 µM of SNP, -0.3 MPa and -0.3 MPa, +200 µM of SNP. Were done the following determinations: germination, first count of germination, speed germination index, hypocotyl length, radicle length, dry mass of hypocotyl and radicle. It was quantified the activity of the antioxidative enzymes, superoxide dismutase, catalase, ascorbate peroxidase and total peroxidase. The experimental design was completely randomized with five replications. The water restriction reduced the germination of sesame seeds, however, the presence of nitric oxide (NO) due to the application of SNP, was beneficial, promoting increase in germination, vigor and seedlings. There was an increase of antioxidative enzymes activity in the period of 0 to 24 hours, demonstrating organization of antioxidative system in all long the time. The association of PEG 6000 to SNP, increased the activity of antioxidative enzymes, evidencing an efficient system of elimination of ROS formed during the exposition to water deficit.Index terms: Sesamum indicum L., sodium nitroprusside, vigor, germination, antioxidative system. Ação protetora do óxido nítrico em sementes de gergelim submetidas ao estresse hídrico RESUMO -O objetivo neste trabalho foi investigar o efeito do óxido nítrico como agente protetor em sementes de gergelim submetidas a diferentes potenciais osmóticos. Os tratamentos, no total de oito, foram: água (controle), água acrescida de nitroprussiato de sódio (SNP) e os demais tratamentos referentes às concentrações de PEG e PEG acrescido de SNP: 0,1MPa, 0,1MPa +200 µM de SNP, -0,2 MPa, -0,2MPa +200 µM de SNP, -0,3 MPa e -0,3 MPa, +200 µM de SNP. Foram feitas as seguintes determinações: germinação, primeira contagem de germinação, índice de velocidade de germinação, comprimento de hipocótilo, radícula e massa seca de hipocótilo e radícula, além da quantificação da atividade das enzimas superóxido dismutase, catalase, ascorbato peroxidase e peroxidases totais. O delineamento estatístico utilizado foi o inteiramente casualizado com cinco repetições. A restrição hídrica reduz a germinação de sementes de gergelim, entretanto, a presença de óxido nítrico (ON) proporciona aumento na germinação e vigor. Há aumento da atividade das enzimas do sistema antioxidante no período de 0 a 24 horas, demonstrando organização do sistema antioxidante nas sementes de gergelim. A associação do PEG-6000 ao SNP aumenta a atividade das enzimas antioxidantes evidenciando um eficiente sistema de eliminação de ERO durante a exposição ao estresse hídrico.Termos para indexação: Sesamum indicum L., nitroprussiato de sódio, vigor, germinação, sistema antioxidante.