Alek Sandro Dutra

Envelhecimento acelerado como teste de vigor para sementes de milho e soja

The evaluation of the seed vigor has been a fundamental tool of quality control program and the accelerated aging test an important procedure for that. This work was carried out in order to search for specific methodologies of evaluation of seed vigor, in laboratory, based on the accelerated aging test. The research was conducted using six seed lots of corn and soybean species, with commercially accepted quality patterns (germination). The prior established conditions for aging were 42oC/96h and 45oC/72h for corn and 41oC/48 and 72h and 42oC/48 and 72h for soybean. For each combination of temperature and aging periods, the seeds were placed into plastic boxes (gerbox), with 40mL of distilled water, distributed on the screen, using single layer and based on the seed weight. For the aging, two chamber types, BOD and water jacketed were used. The moisture content and germination of seed lots, after aging, were determined. The water uptake considering the combinations of temperature/exposure period, the two chamber types and the two procedures of determining seed moisture content was higher when the seeds were conditioned in a single layer compared to weight (constant mass). For the corn, the combination of 45oC/72h with the conditioning of the seeds in only layer was the most efficient method for the separation of the lots with relationship to the vigor. For soybean, the combination 42oC/48h was more efficient in the separation of the lots, not having interference of the method of conditioning of the seeds, in the screen. Considering the results it can be concluded that the single layer distribution should be used for corn and soybean and the BOD chambers should also be used for accelerated aging test for both species.

Electrical conductivity and soybean seedling emergence

A avaliacao do vigor e sua relacao com a emergencia de plântulas em campo e fundamental para a estimativa correta do potencial fisiologico de sementes de soja [Glycine max (L.) Merrill]. O presente trabalho objetivou verificar a relacao entre os resultados do teste de condutividade eletrica (CE) e os da emergencia de plântulas de soja em campo e em laboratorio. Foram estudados niveis de disponibilidade de agua no substrato -0,03; -0,2; -0,4; e -0,6 MPa. Foram avaliados 14 lotes de sementes das cultivares Embrapa 48 e BRS 133. O experimento em campo foi conduzido em tres epocas de semeadura (26/11 e 3 e 10/12/2000); em laboratorio, foram determinados o teor de agua, antes e apos o envelhecimento acelerado (EA) das sementes, a germinacao e o vigor (testes de EA e de CE). A reducao progressiva da quantidade de agua no substrato provocou diminuicao das porcentagens de germinacao e de emergencia de plântulas em laboratorio, de modo que o desempenho germinativo das sementes dependeu dos niveis de estresse hidrico e do vigor da semente. Para lotes de maior vigor da cultivar Embrapa 48, o melhor desempenho ocorreu sob o potencial hidrico de -0,6 MPa. CE pode ser um eficiente procedimento para a avaliacao do potencial fisiologico e desempenho de lotes de sementes de soja, necessitando, porem, que estudos adicionais sejam conduzidos para o estabelecimento de valores ou limites de valores para caracterizar o nivel de vigor das sementes (alto, medio ou baixo) permitindo direcionar de maneira consistente o uso dos lotes de sementes.

Envelhecimento acelerado para avaliar o vigor de sementes de feijão caupi

Seed vigor testing is an important component of quality control programs, and accelerated aging is a possible option in this process. This study was conducted to investigate procedures to assess seed vigor by the accelerated aging test in cowpea (Vigna unguiculata L. Walp) seeds. Samples from Setentao and Epace 10 cultivars, harvested in 1998, 2001, 2002 and 2003 were used. During the experimental period seeds were stored in plastic bags and kept at 10oC and 50% R.H. Accelerated aging was performed at 40, 42 and 45oC during 24, 48, 72 and 96 hours; seeds were kept in plastic boxes with 40mL of distilled water in a BOD chamber. Seeds were tested for germination and moisture content before and after aging. The best condition to evaluate physiological potential of cowpea seeds was the combination 42oC/48 hours.

QUALIDADE FISIOLÓGICA DE SEMENTES DE FEIJÃO-CAUPI EM QUATRO REGIÕES DO ESTADO DO CEARÁ

The present study aimed to evaluate the physiological quality of cowpea seeds from the cultivars Sempre verde, Setentao, Patativa, Pingo de ouro, Aparecido and Epace-10 collected in four different regions of the State of Ceara. The seeds were produced in Quixada, Pentecoste, Limoeiro do Norte and Morada Nova Counties during 2004. The seeds were tested for germination, first germination counting, seedling emergence, emergence speed index, and electric conductivity. The physiological quality of the seeds produced in Pentecoste and Limoeiro do Norte counties was better than the physiological quality of those produced in Quixada and Morada Nova, for the majority of the cultivars tested. The seeds of the cultivars Sempre Verde, Setentao, Pingo de Ouro and Aparecido showed superior performance, the cultivar Epace-10 showed intermediary performance and the cultivar Patativa showed inferior performance.

Condutividade elétrica em sementes de abóbora, híbrido Bárbara

The electrical conductivity in the soaked seed solution has been used successfully to evaluate seed vigor. This work was developed with the objective of determining the adequate procedures to evaluate the electrical conductivity test of pumpkin (Cucurbita moschata Duch ex. Lam) seeds. For pumpkin, hybrid Barbara, five lots of seeds, in both stages, were used, all with quality patterns (germination) above the minimum demanded by commercialization. The standard germination, first countig of germination, seedling emergency, and emergency speed index and electrical conductivity (EC) test were run. For the EC test two volumes of water (50 and 75mL), three temperatures (20, 25 and 30oC) and eight period of seed soaking (1, 2, 4, 8, 12, 16, 20 and 24 hours) were used. So, it can be concluded that the EC test can be conducted using 50 seeds, 25oC, 75mL and 8h of embibition period for pumpkin seeds.

Germinação de sementes de Senna siamea (Lam.) H.S. Irwin E Barneby: Caesalpinoideae

Senna siamea is a tree from Thailand that has adapted well to the climatic conditions of the Northeast of Brazil, that has been used for arborization, hedges and timber production. This research was divided in two experiments that aimed to identify methods to break dormancy and verify how temperature and light can affect germination of its seeds. In the experiment the germination percentages of hard and dead S. siamea seeds were determined using the treatments: humid heat, immersion in sulfuric acid and hot water, mechanical scarification, aiming at breaking dormancy and the control. In the second experiment, S. siamea seeds that had been immersed in sulfuric acid were placed on filter paper and submitted to five light period/temperature combinations: continuous light and constant temperature (25oC), continuous light and two different temperatures (35oC/8h and 20oC/16h), continuous dark and constant temperature (25oC), continuous dark and two different temperatures (35oC/8h and 20oC/16h), and different light periods and temperatures (light/35oC/8h and dark/20oC/16h). From the experiments it was concluded that S. siamea seeds present dormancy. The best treatments for breaking dormancy were mechanical scarification and sulfuric acid. The seeds were indifferent to the light and their germination was not influenced by the tested temperatures.

Teste de deterioração controlada na determinação do vigor em sementes de algodão

Vigor evaluation has been a basic tool in programs for seed quality control, and the controlled deterioration test is an important part of the process. The present research was developed with to verify the efficiency of the controlled deterioration test for the evaluation of cotton seed vigor. The initial quality for five lots of seeds was evaluated by the germination test, germination at first count, emergence in the field, speed of emergence index and seedling dry weight. The seed water content was adjusted tor 20 and 24%, and they were then submitted to controlled deterioration in a water bath at 40 and 45oC, for 24 and 48 hours. The combination of 24% of water in the seed for 48 hours and 40oC in the controlled deterioration test was efficient for separating the cotton seed lots.