Eduardo Fontes Araújo

AVALIAÇÃO DA QUALIDADE FISIOLÓGICA DE SEMENTES DE MILHO-DOCE PELO TESTE DE ENVELHECIMENTO ACELERADO 1

This study was carried out to evaluate methods of breaking Stylosanthes scabra seed and fruit hardness, separately. The methods evaluated were: control dry heat at 85°C for 10, 12, and 14 hours, immersion in concentrated sulphuric acid for five and 10 minutes, and immersion in boiling water for one minute. The germination test consisted of evaluating normal seedlings (germination percentage), abnormal seedlings, hard seeds and dead seeds. It was concluded that the best treatment was seed scarification with concentrated sulfuric acid for five and 10 minutes. In relation to fruit scarification, an immersion time longer than 10 minutes deserves further study. The dry heat treatment did not overcome the impermeabily of the seed covering layers. Boiling water led to the death of more than 90% of the seeds.This study aimed to evaluate the efficiency of the accelerated aging test at different periods and exposure temperatures in evaluation of the physiological seed quality of sweet corn lots. The assays were carried out from February to June 2000 at the Laboratorio de Sementes of the Phytotechny Department in the Universidade Federal de Vicosa - MG. Corn seeds of the cultivar BR 400 (Super-Doce) were used into four lots obtained from a drying process at 30, 40, 50 and 60oC and an environmental relative humidity of 60%. Initially the moisture content of the seeds was determined and then the seed physiologic quality were evaluated by the germination, first germination count and cold tests. The entirely randomized experimental design was used for these tests. Two experiments were carried out in evaluating the methodology of the accelerated aging test. The first experiment was carried out at 42oC temperature on an entirely randomized design and a factorial scheme 4x4 (four aging periods: zero, 48, 72 and 96 hours and four seed lots) arranged on a split-plot design over time. The second experiment was carried out at 45oC temperature by using the same design and a factorial scheme 4x4 (four aging periods: zero, 24, 48 and 72 hours and four seed lots). In both experiments, the 45oC temperature and the 24hour-exposure to the accelerated aging provided a better differentiation among lots with different quality levels. The 42oC temperature over a 72 hour-period allowed a better differentiation between seed lots as to their physiologic quality.

Uso do teste de tetrazólio para avaliação da qualidade fisiológica de sementes de abobrinha

165RESUMO – O trabalho teve como objetivo desenvolver metodologia apropriada para o uso doteste de tetrazolio em sementes de abobrinha, visando determinar a viabilidade e o vigor. Osseguintes procedimentos foram avaliados: umedecimento das sementes em papel toalha por 16 e24h, a 25°C; imersao direta em agua, em câmara BOD, a 40°C, por 15, 30 e 60 minutos para a remocaodo tegumento e por mais 30 e 60 minutos para retirada da membrana que envolve o embriao. Osembrioes foram entao imersos em solucao de tetrazolio a 0,05 e 0,075% por 30, 60 e 90 minutos, emcâmara BOD, a 40°C, para coloracao. Paralelamente, foram conduzidos testes de germinacao evigor, estabelecendo-se cinco classes de viabilidade e vigor. A metodologia desenvolvida foiaplicada a oito lotes, sendo aferida com os resultados dos testes de germinacao, envelhecimentoacelerado e emergencia de plântulas em areia. O teste de tetrazolio mostrou-se eficiente para avaliara viabilidade e o vigor das sementes de abobrinha. O metodo de pre-condicionamento mais eficientefoi imersao direta em agua, a 40°C, por 30 minutos para a remocao do tegumento e por mais 30minutos para a retirada da membrana interna. A coloracao ideal dos embrioes foi obtida apos 60minutos de imersao em solucao de tetrazolio a 0,05 ou 0,075% a 40°C.Termos para indexacao:

Primed carrot seeds performance under water and temperature stress

Uniformity and percentage of seedling emergence of direct-seeded vegetables have a major impact on their yield and quality. Depending on temperature and soil water potential, carrot seeds performance in the field is poor justifying the use of techniques to accelerate the germination and seedling emergence. The objective of this work was to evaluate the effects of priming treatments, with and without aeration, on carrot seeds performance under water and temperature stress. Two seed lots of carrots, Brasilia cultivar, were primed in PEG 6000 -1.0 and -1.2 MPa solutions, for four and eight days, at 20oC, using two imbibition methods: priming in paper towel moistened with the respective solutions and immersion into aerated osmotic solutions. Non-primed seeds were used as control. After priming, the seeds were dried at room temperature until reach initial seed moisture content. The seeds were submitted to the following tests: germination, first count, seedling emergence in the field, germination at sub-optimal (15oC) and supra-optimal temperature (30oC) and germination under water stress (PEG 6000 at -0.4 MPa). Priming in -1.0 and -1.2 MPa PEG 6000 during four and eight days can be useful for improving carrot seedling emergence in the field and seed performance under supra and sub-optimal temperatures. Aeration of the peg solution was beneficial when seeds were primed at -1.2 MPa for eight days.

Germination and vigour of primed asparagus seeds

The osmotic conditioning or priming is considered a promising technique to speed up germination and to improve seed performance. Four seed lots of asparagus, Mary Washington cultivar, were primed at 25°C for seven or 14 days using PEG 6000 at -1.0 or -1.2 MPa, or sea water at -3.3 MPa; or for three days in distilled water. The physiological quality of the seeds was evaluated by standard germination, first count germination, speed of seedling emergence, and germination percentage and seedling fresh and dry weights after controlled deterioration test. Primed seeds presented higher germination speed, independently of their initial physiological quality. Beneficial effects of priming on germination and vigour were more expressive in the seed lot of low physiological quality. Priming in PEG 6000 at -1.0 MPa for 14 days was the most beneficial treatment to improve asparagus seeds performance.

Comparação de modelos matemáticos para descrição das curvas de dessorção de sementes de milho-doce

This work had the goal to determine the desorption curves of seeds of sweet corn cultivars Superdoce and Doce Cristal, and to adjust mathematical models to obtained data. Corn seeds were submitted to desorption under different temperature conditions (30, 40, 50 and 60°C), associated with different relative humidity (30, 40, 50 and 60%) until reaching the equilibrium humidity. The following models of regression analysis were adjusted to the experimental data: Henderson-Thompson, Chung-Pfost, Copace, Sigma-Copace, Sabbah and Smith. Seeds of both cultivars showed similar hygroscopic equilibrium. For both cultivars, the equations of Chung-Pfost, Sabbah and Smith, showed the best adjustments to the experimental data, with slight superiority of the first one.

Influência do tipo de fruto, peso específico das sementes e período de armazenamento na qualidade fisiológica de sementes de mamão do grupo formosa

The present study evaluated the influence of the fruit type, specific seed weight and storage on the germination and vigor of papaya seeds of the Solo group. After harvest the fruits were classified as small, medium or large. The seeds were extracted manually, washed and placed to dry in the shade. After drying, the seeds were processed in a pneumatic machine to separate light materials and also through a gravity table machine, where the seeds were separated into three classes: light, intermediate and heavy. The seeds were placed in paper bags, stored in a cold chamber and evaluated for germination and vigor (First Count of GT, Seedling Size and Accelerated Aging test) at the start of the experiment and after 3 and 6 months of storage. The best germination and vigor results were found when heavy seeds were used. High seed quality was preserved until the third month of storage.

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

Good quality seeds are indispensable for successful crop establishment. A more precise analysis of seed quality requires a complementation of the information supplied by the germination with vigor tests to allow selection of the best lots for commercialization and sowing. Among these tests, the electric conductivity test is important. The objective of this study was to develop a suitable methodology for the electric conductivity test in mung bean seeds, with treatments of different imbibition periods and seed numbers. Six seed lots were used with the following treatments: 100, 75 and 50 seeds imbibed in 75 mL of 25 °C distilled water, and evaluations after 3, 6, 9, 12, and 15 hours of imbibition. The electrical conductivity test done with four subsamples of 50 pure seeds soaked in 75 mL of distilled water at 25 °C, permits a separation of the lots after three hours of soaking, and this procedure would make a quality evaluation of mung bean seeds viable.

Potato plant growth and macronutrient uptake as affected by soil tillage and irrigation systems

The objective of this study was to evaluate potato plant growth and macronutrient uptake, as affected by soil tillage methods, in sprinkle and drip irrigated experiments. Eight treatments were set: T1, no tillage, except for furrowing before planting; T2, one subsoiling (SS); T3, twice rotary hoeing (RH); T4, one disc plowing (DP) + twice disc harrow leveling (DL); T5, 1DP + 2DL + 1RH; T6, 1DP + 2DL + 2RH; T7, 1SS + T6; T8, one moldboard plowing (MP) + 2DL. Treatments were arranged in a randomized block design with four replications. In both irrigation systems, plants presented higher emergence velocity index (EVI), when the soil was not tillaged, and the EVI was inversely related to the maximum tuber dry mass production. In both experiments, a functional direct relationship was found between the leaf area index and maximum tuber dry mass yield. The growth of plant organs (tuber, leaf, stem and root) and the macronutrient (N, P, K, Ca and Mg) contents in potato plant responded positively to a deeper soil revolving caused by plowing, especially with moldboard plow.

Germinação e vigor de sementes de cenoura osmocondicionadas em papel umedecido e solução aerada

The problems regarding carrot seeds performance in the field are constant justifying the use of techniques to accelerate germination and seedling emergence. The objective of this study was to evaluate the effects of two imbibition methods during priming on carrot seed germination and vigour.. Two seed lots of carrot, Brasilia cultivar, were primed in PEG 6000 -1.0 and -1.2MPa solutions for 4 and 8 days, at 20o C, using two imbibition methods: paper towel moistened with the respective solutions and immersion in aerated osmotic solutions. Non-primed seeds were used as control. The seeds were submitted to the following tests: germination, first count, percentage and speed of seedling emergence in the field at 10 and 25 days after sowing and primary root length. Priming in PEG 6000 for four days was effective in increasing the percentage and speed of germination and seedling emergence in the field. For primary root length, priming in PEG 6000 -1.2 MPa aerated solution was superior to moistened paper treatment.

Uso de hipoclorito de sódio para degradação do endocarpo de sementes de cafeeiro com diferentes graus de umidade

The objective of this study was to evaluate the combinations between sodium hypochlorite concentrations and presoaking times that would provide higher germination of coffee seeds with moisture contents from 13 to 33% (w.b.). The seeds of Catuai Vermelho IAC 44 variety were dried in the shade until they reached the desired moisture contents. Five assays were accomplished, one for each moisture content of the seeds (13, 18, 23, 28 and 33%). Each assay consisted of 12 treatments, each one consisting of combinations of five sodium hypochlorite concentrations (3, 4, 5, 6 and 7% active chlorine) in the presoaking solution and two presoaking times (3 and 6 hr), besides the seeds with or without endocarp that were manually removed (control). The seeds were evaluated, by using the following tests: first germination counting, germination, germination speed index and seedling vigor. According to the results, the presoaking of the coffee seeds into sodium hypochlorite at 6% concentration active chlorine for three hours promoted an efficient degradation of the endocarp, besides providing germination speed index similar to the control, when seeds showed initial moisture content between 23 and 33%. In those seeds with moisture content at 18 and 13%, the presoaking in sodium hypochlorite led to an inferior germination performance of the seeds relative to the seeds without endocarp that was manually removed, regardless of the combination between concentration and the presoaking time.