Sebastião Carneiro Guimarães

Pre-harvest desiccation: effects on the physiological quality of soybean seed.

Temperature fluctuations associated with high rainfall and the oscillating relative humidity of the air during the pre-harvest stages of seed maturation may result in losses in physical and physiological quality and also in seed health. Pre-harvest desiccant application helps to reduces seed exposure to unfavourable climate conditions and reduce seed vigor and germination. The object of this research was to determine the effects of the application period of desiccants and of early harvesting on soybean seed quality. The experiments were conducted in Alto Garcas, MT, with the cultivars MG/BR-46 Conquista and FMT Tucunare in the 2005/2006 growing season, and with BRS MT Pintado and FMT Tucunare in 2006/2007. The experimental design was a randomized block in a factorial arrangement 6x2x2x2 [6 treatments (5 desiccants and 1 control), 2 application times, 2 harvest times and 2 storage periods]. Five desiccant treatments were evaluated: paraquat, diquat, paraquat + diquat, paraquat + diuron and glyphosate, applied at the R6.5 and R7 growing stages, which were compared to a control treatment. Seeds were harvested at two stages: first, when moisture content reached 17% to 20% (early harvest), and secondly, 12% to 13% (normal harvest). Seeds from early harvesting were dried to 12% to 12.5% moisture content in a forced air chamber at temperatures ranging from 38 oC to 40 oC. Seed quality was evaluated by the following tests: germination, seedling vigor classification, tetrazolium, field seedling emergence and seedling growth. Paraquat, diquat, paraquat + diquat and paraquat + diuron as pre-harvest desiccants do not affect seed physiological quality but glyphosate causes phytotoxic damage to seedling roots. With the exception of glyphosate, pre-harvest desiccation at the R6.5 and R7 growth stages results in the production of seeds having a similar quality. Early harvest results in the production of higher quality seeds compared to those from a normal harvest.

TESTES DE VIGOR EM SEMENTES DE ALGODOEIRO HERBácEO 1

The objective of this work was to study the efficiency of controlled deterioration and traditional and modified accelerated aging tests in order to evaluate the physiological potential of cotton seeds. Eight seed lots of cotton variety CD 406 were submitted to a controlled deterioration test, with seed moisture content adjusted to 15, 18, 21, and 24%. The seeds were submitted to aging in a double boiler at 41, 43, and 45°C for 24 hours. The accelerated aging test in chambers containing either water (traditional method) or saturated NaCl solution (modified method) was performed under three temperature-time conditions: 41°C/48h, 42°C/60h, or 45°C/72h. It was concluded that the controlled deterioration test, performed with seed moisture content artificially adjusted to 15%, followed by aging in a double boiler at 43°C for 24 hours, as well as the accelerated aging test with the use of a saturated NaCl solution conducted at 41°C/48h are the most promising combinations to evaluate the physiological potential of cotton seeds. Traditional accelerated aging at 45°C/72h was exceedingly harsh on the seeds, causing seed viability loss

Influência da temperatura e da luz na germinação de sementes de couve-cravinho (Porophyllum ruderale (Jacq.) Cass.)

The knowledge of the biology and of the ecology of weeds precede the elaboration of agronomic strategies for weed control, reducing the costs of the productive process. Certain plants, in addition to other biological characteristics of importance, have their germination capacity influenced by abiotic factors such as temperature and brightness. With the objective of evaluating the germinative response of Porophyllum ruderale seeds, in function of temperature and brightness, two experiments were carried out: in experiment 1, seeds of P. ruderale were put to germinate at three temperatures (20, 25 and 30oC) in two substrates (among and on-paper); in the second experiment, the effect of the light was evaluated in the germination of P. ruderale seeds. The influence of white light, red wavelength, extreme red and light absence were evaluated. Greaterer germination was obtained at temperatures of 25 and 30oC. As the light influenced the germinative process it was verified that seeds of P. ruderale are sensitive to brightness, where the light absence provoked the drastic reduction in the germination of the seeds.

Germinação de sementes de Amburana acreana (Ducke) A. C. Sm. submetidas a diferentes condições de temperatura e de estresse hídrico

The aim of this study was verify the influence of the temperature and water stress in the seeds germination and seedling formation in Amburana acreana. Two assays had been carried through. In the first one, the seeds had been placed to germinate in the temperatures of 20, 25, 30, 35 and 40°C. In the second, the seeds were placed to germinate in paper towel moistened with solutions of polietilenoglicol 6000 in the following osmotic potentials: zero, -0.2, -0.4, -0.8, -1.0 and -1.2MPa, in 30°C. The germination of the seeds and normal seedling was evaluated during 30 days, in the five replications of 20 seeds, and was considered germinated when the seeds have primary root with at least five millimeters of length and positive geotropic curve. The better results, in the first assay, were found between 30 and 35°C, with higher germination and normal seedling percentage and also those were the treatments where the germination process occurred in lesser average time. In the second assay, the percentage of germinated seeds reduced with the availability of water in the substrate at -0.4MPa and was zero at -1.0 and -1.2MPa. Seedling was reduced at -0.2MPa and was completely inhibited at -0.4 and -0.8MPa. From this study we recommend the temperature of 30°C for germination test because offer better conditions to the germination process with better percentage of seedling than the other temperatures. It was concluded that the reduction of the availability of water reduces the germination and seedling process and the limits for germination occur between zero and -1.0MPa and for seedling process between zero and -0.4MPa.

Vigor de sementes e desempenho agronômico de plantas de algodão

Seed vigor may influence seedling emergence, plant field performance and yield, depending on species and environmental factors. Thus, one of the most important challenges to the researcher is to evaluate the influence of the physiological potential of seeds on the plant cycle. The objective of this study was to evaluate seed vigor effects on the morphophysiological characteristics of cotton plants, as well as on cotton seed and fiber yield. Three seed lots of the cultivar FMT 701 (produced in the 2005/2006 cropping year) were selected, based on laboratory evaluations. Seed vigor effects were evaluated in the field during the 2006/2007 and 2007/2008 seasons. The experiments were conducted in Jaciara county, Mato Grosso state, Brazil. The percentage of emerged seedlings, speed of emergence index, plant height, number of branches bearing cotton balls, number of nodes, number of fruiting positions, number of cotton balls, cotton seed and fiber production were evaluated. Initial and reproductive performances were found to be dependent on seed vigor and other factors. High vigor plants produced more fiber and seed.

Germinação de sementes de Conyza canadensis e C. bonariensis em função da presença de alumínio no substrato

A germinacao das sementes pode ser fortemente influenciada pelas condicoes ambientais, afetando o estabelecimento de comunidades floristicas. As plantas daninhas, apesar das caracteristicas de rusticidade e capacidade de suas sementes germinarem em condicoes de estresse ambiental, podem sofrer o efeito direto da presenca de elementos toxicos no substrato. O aluminio, presente em solos com pH baixo, pode interferir negativamente no processo germinativo de sementes de especies cultivadas e tambem de plantas daninhas. No presente trabalho, objetivou-se estudar o efeito toxico da presenca de aluminio no substrato durante a germinacao de sementes de Conyza. A germinacao foi reduzida pela presenca de aluminio no substrato, havendo decrescimos significativos a partir de 1,5cmolc dm-3 para as sementes de ambas as especies, enquanto a velocidade de germinacao foi prejudicada a partir da menor concentracao (0,5cmolc dm-3) de aluminio testada. Esses resultados demonstram que as sementes de ambas as especies sao sensiveis a presenca de aluminio no substrato de germinacao.

Effects of environmental factors induced in the germination of Chaptalia nutans (L.) Polack seeds

Chaptalia nutans is species whose medicinal value has been studied thoroughly, and aspects regarding seed germination are important to define better propagation practices. The objective of the present study was to evaluate the germination response of C. nutans seeds to conditions of light and temperature, as well as osmotic and saline stresses and potassium nitrate. Four experiments were conducted: a) combination of four temperatures (20oC, 25oC, 30oC and laboratory atmosphere) with two light conditions (presence or absence); b) ten levels of osmotic stress induced with manitol (0.0; -0.05; -0.1; -0.2; -0.3; -0.4; -0.5; -0.6; -0.7 and -0.8 MPa); c) eight levels of saline stress induced with NaCl (0.0; -0.1; -0.2; -0.3; -0.4; -0.5; -0.6 and -0.7 MPa) and d) combination of two levels of potassium nitrate (presence or absence) with two temperatures (20 and 25 oC) and two levels of light (presence or absence). Germination of C. nutans seeds was maximized under light, at constant temperatures of 25 , 30 oC, or room temperature between 19 and 31 oC. There was no germination reduction with osmotic stress of up to -0.6 MPa and saline stress of up to -0.5 MPa. The addition of potassium nitrate did not promote any increase in the germination.

Métodos para o condicionamento fisiológico de sementes de milho

This study aimed to evaluated different methodologies and water potentials for priming of maize seeds, in order to increase vigor. The experiment was carried out following a completely randomized design, in a factorial scheme 4x3+1, with four water potentials (0.0, -0.4, -0.8 and -1.2 MPa), three priming methods (immersion in non-aerated solution, immersion in aerated solution, paper roll) and a control. After priming, the seeds were dried and evaluated for water content, percentage and first germination count, seedlings length and dry mass, cold test and vigor index. The water potential recommended for priming maize seeds, in polyethylene glycol 6000 is -0.4 MPa for 24 hours. The priming procedures in towel paper rolls improve the quality of maize seeds.

Qualea grandiflora Mart.: TEMPERATURA NA GERMINABILIDADE DE SEMENTES

Qualea grandiflora Mart. ocorre em matas de galeria e cerrado, sendo conhecida popularmente como pau- terra. Com o objetivo de obter informacoes sobre a propagacao reprodutiva dessa especie foi estudado o efeito da temperatura sobre a germinabilidade das sementes. As temperaturas utilizadas foram: 15, 20, 25, 30, 35 e 40 oC. As sementes foram semeadas em substrato papel-toalha, na forma de rolo, com quatro repeticoes, sendo a unidade experimental constituida por um rolo com 25 sementes. O experimento seguiu o delineamento inteiramente casualizado com seis tratamentos e quatro repeticoes. Houve emissao de raiz primaria em temperaturas de 15 a 40 oC. Valores entre 78 e 93 % foram obtidos numa ampla faixa de temperaturas, entre 15 e 35 oC. A formacao de plântulas normais ocorreu em faixa mais restrita, entre 20 e 35 oC. A protrusao de raiz iniciou no setimo dia apos a semeadura, exceto a 15 oC que proporcionou um processo lento e gradativo, iniciando no decimo quarto dia apos a incubacao. A 40 oC a germinabilidade foi inferior a 15 % e nao houve formacao de plântulas normais. Para germinacao de sementes de pau-terra, recomenda-se a faixa de temperatura entre 20 e 30 oC.