Maria Cristina de Figueiredo e Albuquerque

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.

Qualidade fisiológica de sementes de algodoeiro submetidas a tratamentos químico e biológico

An alternative to chemical treatments is the biological treatment of seeds with bioprotectors. Trichoderma spp. has been considered efficient in the control of fungi and bacteria. This study was carried out with the objective of evaluating the efficiency of the treatments of cottonseeds with the fungicides: carboxin+thiram, carbendazin+thiram and flutolanil, comparing them with T. harzianum, in the seed germination and vigor and in the promotion of seedling growth. The standard germination, emergence in sand and in the field, germination at low temperature, index of germination speed, dry matter and length of the aerial part of the seedlings were evaluated. Seeds treated with T. harzianum, carbendazin+thiram and carboxin+thiram showed higher germination and emergence and the first two also resulted in more vigorous seedlings. Seeds treated with carboxin+thiram produced smaller seedlings with lower dry matter.

Fruit, seed and seedling morphology of Jatropha elliptica Müll. Arg. (Euphorbiaceae).

The aim of this work was to describe the morphology of the fruit, the seed and the development of the seedling of Jatropha elliptica Mull. Arg. The fruits were collected in September and October (2002), in the Experimental Farm at Universidade Federal Mato Grosso, in Santo Antonio de Leverger-MT. 50 fruits and 50 seeds were utilized to describe the fruit and the seed morphology. For the characterization of the germination stages, four repetitions of 20 seeds were used, sowning upon blot paper, in clear plastic boxes, moisten with giberelic acid (400 ppm), kept in a germination chamber, at 30 oC and with an eight hours photoperiod, during 45 days. The fruit of J. elliptica is dry, with three cocas, a hard endocarp, and shows an explosive dehiscence. The seed is oval, albuminous, has a smooth testa and a marmoreal color, with a caruncule in the ventral part, a visible hilum in the base and the distinct longitudinal rafe. The germination is epigeous and phanerocotyledonal. The germination average time is from 13 to 25 days. It was possible to describe and to illustrate, in a distinct form, J. elliptica fruit, seed and seedling morphologies, which behaved in a sufficiently homogeneous and trustworthy way for the identification.

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.

Sobrevivência e crescimento inicial de espécies arbóreas nativas do Cerrado em consórcio com mandioca

O objetivo deste trabalho foi avaliar a sobrevivencia e o crescimento inicial de seis especies arboreas do Cerrado em consorcio com mandioca ( Manihot esculenta ), com ou sem adubacao fosfatada. Utilizou-se o delineamento experimental de blocos ao acaso, em arranjo fatorial 6x2x2, com quatro repeticoes. As variaveis consideradas foram as especies: Anadenanthera colubrina var. cebil (angico‑vermelho), Anacardium occidentale (caju), Dipteryx alata (cumbaru), Hymenaea stigonocarpa (jatoba), Hancornia speciosa (mangaba) e Sclerolobium paniculatum var. rubiginosum (taxi‑branco), em monocultivo ou em consorcio com mandioca, com ou sem adubacao fosfatada. Uma distância fixa de 3x3 m foi usada para as especies arboreas e de 1,00x0,60 m para amandioca. Ate a idade de 20 meses, as especies arboreas foram avaliadas quatro vezes quanto a altura e ao diâmetro do coleto. A producao de biomassa da mandioca foi avaliada aos 20 meses. A taxa media de sobrevivencia das especies arboreas foi crescente na seguinte ordem: cumbaru (79%), taxi-branco (86%), jatoba (95%), mangaba (98%), angico (99%) e caju (100%). O taxi-branco apresentou maiores taxas de crescimento relativo em diâmetro e altura, enquanto jatoba e cumbaru apresentaram os menores valores. A adubacao fosfatada favoreceu apenas ao taxi-branco. A produtividade de mandioca nao foi afetada pelo consorcio. Caju, angico‑vermelho e taxi‑branco sao as especies mais indicadas para o consorcio com mandioca no Cerrado.

Desempenho de sementes de algodão após o processamento e armazenamento

O trabalho foi realizado com o objetivo de estudar os efeitos do processamento e armazenamento na qualidade de sementes de algodao, cultivar ITA 90-2, produzidas em Campo Verde-MT, nos anos agricolas de 2001 e 2002. As sementes foram analisadas antes e apos cada etapa do processamento e durante o armazenamento. O delineamento experimental foi o inteiramente casualizado, com quatro repeticoes. Os tratamentos foram constituidos das etapas do processamento: antes e apos a colheita mecânica, apos 30, 60 e 85 dias de armazenamento em fardo no campo, apos descarocamento mecânico, apos deslintamento quimico, apos beneficiamento em mesa de gravidade e apos 15, 30, 60 90 e 120 dias de armazenamento. No ano de 2002 foram apenas 30 dias de armazenamento. As medias foram comparadas pelo teste de Scott-Knott a 5%. Os resultados obtidos permitem concluir que o armazenamento temporario, em fardos no campo, por ate 85 dias, nao causa perda imediata na qualidade das sementes; o descarocamento mecânico nao tem efeito prejudicial imediato sobre o vigor das sementes e a porcentagem de germinacao mantem-se dentro do padrao (70%) para o comercio de sementes por ate seis meses apos a colheita.

Performance of cotton seeds submitted to different types of stress

Temperature and moisture variations during the plantlet emergence period are the most important types of stress, representing the greatest hazards in cotton emergence. The objective of this study was to investigate the influence of type of stress on the germination performance of cotton seeds and determine germination test effectiveness at low temperature. Five seed lots were previously submitted to moisture content, germination, and vigor tests (germination at low temperature). The seeds from each lot were then submitted to temperature (18oC and 35oC) and water availability (40% and 80%) stresses conditions. After germination was conducted under a stress situation, evaluations were made for plantlet emergence percentage and velocity, and root length and above-ground part length. Root length and above-ground part length at 18oC were more effective than plantlet emergence percentage in discriminating the seed lots with respect to their physiological potential. Seed exposure to stress produced by high water availability and low temperature cause reduced germination performance of the cotton seed lots and may represent the greatest hazards during plantlet emergence. The germination test at low temperature is effective to estimate plantlet performance under low and high temperature and low moisture conditions.

Superação da dormência em sementes de Bromelia balansae (Bromeliaceae)

The effects of temperature and substrates and different methods to overcome dormancy of Bromelia balansae (caraguata) seeds were evaluated. The fruits were collected on Chapada dos Guimaraes, Mato Grosso State, Brazil. The experimental design was completely randomized with five replications of 50 seeds for each sample. On the first experiment the seeds were submitted to six treatments: a) 25°C and over the paper, b) 30°C and over the paper, c) 25°C and between papers, d) 35°C and between papers, e) alternating 25/30°C and over the paper f) alternating 25/30°C and between papers. On the second experiment we evaluated a) immersion in concentrated sulfuric acid PA (98%) during 60 minutes, b) immersion in concentrated sulfuric acid PA (98%) during 15 minutes, c) immersion in concentrated sulfuric acid PA (98%) during 5 minutes, d) mechanical scarification with no 80 sandpaper, e) control. On the third experiment we evaluated a) sulfuric acid PA (98%) for 1 minute; b) sulfuric acid PA (98%) for 3 minutes; c) sulfuric acid PA (98%) for 5 minutes; d) mechanical scarification with no 80 sandpaper, e) immersion in water at 100oC and f) control. On the two first experiments the seed germination was low. On the third experiment the seed germination was higher in the treatments with sulfuric acid (40% to 70%). The seeds of B. balansae present seedcoat dormancy that is overcome with the sulfuric acid immersion 100% for 1 minute.

Influência da escarificação e da temperatura sobre a germinação de sementes de Samanea tubulosa (Benth.) Barneby & J.W. Grimes (sete cascas)

Samanea tubulosa (Benth.) Barneby & J.W Grimes (sete cascas) e uma planta arborea nativa do Pantanal Matogrossense, cujas sementes possuem dormencia provavelmente causada pela impermeabilidade do tegumento a agua. O presente trabalho foi conduzido com o objetivo de comparar a eficiencia da escarificacao mecânica e quimica para superar a dormencia tegumentar e o efeito da temperatura sobre a germinacao de sementes de sete cascas. Foram empregados quatro diferentes procedimentos de escarificacao: testemunha (sem escarificacao); a escarificacao mecânica; a escarificacao com acido sulfurico durante cinco minutos e a escarificacao com acido sulfurico durante dez minutos. Os niveis de temperatura empregados foram de 20, 25, 30 e 35oC. A semeadura foi realizada em papel toalha germitest, na forma de rolo. O delineamento experimental adotado foi o inteiramente casualizado com os tratamentos em esquema fatorial 4x4. Para cada tratamento, foram utilizadas quatro repeticoes de 25 sementes. Foi avaliada a porcentagem de germinacao das sementes, utilizado como criterio emissao da raiz primaria com 2 mm de comprimento. Foi observado que a especie S. tubulosa possui dormencia tegumentar causada pela impermeabilidade do tegumento a agua. As escarificacoes quimica com acido sulfurico por cinco e dez minutos foram eficientes para superacao da dormencia e as combinacoes de escarificacao com temperatura que promoveram maiores porcentagens de germinacao para a especie foram a escarificacao com imersao em acido sulfurico durante cinco e dez minutos e as temperaturas de 25, 30 e 35oC.

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.