Potencial fisiológico de sementes de milho hidratadas pelo método do substrato de papel toalha

Na avaliação da qualidade de sementes pode ser necessária a hidratação das mesmas, como ocorre no teste de deterioração controlada que requer a uniformização do teor de água na amostra de sementes antes do processo de deterioração. Objetivou-se com o presente trabalho avaliar o potencial fisiológico de sementes de milho após a hidratação pelo método do substrato de papel toalha, sob diferentes temperaturas e quantidades de água no substrato, para elevar o teor de água para 15%, 20% e 25%. Foram avaliadas três quantidades de água no substrato (2,0; 2,5 e 3,0 vezes a massa do papel), sob temperaturas de 20 e 30°C. A qualidade inicial das sementes e após a hidratação foi determinada pelos seguintes testes: teor de água, massa de mil sementes, germinação, massa seca de plântulas, teste de frio, envelhecimento acelerado, condutividade elétrica, tetrazólio, porcentagem e velocidade de emergência das plântulas em campo. Os dados obtidos foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey, a 5%, seguindo o delineamento inteiramente casualizado em esquema fatorial (3x2), independentemente para cada teor de água. A hidratação pelo método do substrato de papel toalha não afetou a germinação de sementes de milho, independentemente da temperatura e das proporções de água no substrato. As proporções de 2,0 e 2,5 vezes a massa do substrato papel toalha em água para a temperatura de 30°C e de 3,0 vezes a massa do substrato para a temperatura de 20°C não alteraram o potencial fisiológico das sementes, mostrando-se adequadas para hidratação de sementes de milho para teores de água de 15, 20 e 25%.In the evaluation of the seed quality it may be necessary the hydration of the seeds, as in the controlled deterioration test that requires uniformization in the moisture content of the seed lots before the process of deterioration. The goal of the paper was to evaluate the physiological potential of maize seeds after the hydration through the method of paper towel substrate, under different temperatures and amounts of water in the substrate, for raising the water content to 15%, 20% and 25%. Three amounts of water were evaluated in the paper towel substrate (2,0; 2,5 and 3,0 times the paper mass), under temperatures of 20 and 30º C. The quality of the seeds, both before and after the hydration, were determined by the following evaluations: moisture content, mass of thousand seeds, germination, seedlings dry weight, cold test, accelerated aging, electrical condutivity, tetrazolium, percentage and speed of emergence of seedlings on field. The experiment was conducted in a completely randomized design outlining in a factorial scheme (3x2), independently for each moisture content. The data were submitted to analysis of variation and the average compared by the Tukey test at 5%. The hydration by the method of paper towel substrate did not affect the germination of the maize seeds, independently of temperature and amount of water in the substrate. The proportions of 2,0 and 2,5 times the mass of paper towel substrate under temperature of 30ºC and of 3,0 times the mass of substrate under temperature of 20ºC did not affect the physiological potential of seeds, being adequate in the hydration of maize seeds for the moisture content of 15, 20 and 25%

Doses e épocas de aplicação de nitrogênio em cobertura na qualidade fisiológica de sementes de milho doce

The amount and timing of nitrogen application can favor seed quality, such as increasing protein content, which is an important constituent for embryo development. The objective of this study was to evaluate the physiological quality of sweet corn seeds collected from plants cultivated with different dosages and timings of nitrogen top-dressing applications. Seeds of the BR 400 variety (Super Sweet) were used obtained from plants submitted to dosages of 0, 40, 80 and 120kg ha -1 of N in two top-dressing applications (vegetative and reproductive stages). The weight of 100 grains, germination, first count of germination test, dry weight of normal seedlings from the germination test, seedling growth, cold test, accelerated aging, tetrazolium vigor and electric conductivity and emergency speed rate were determined. Data was submitted to an analysis of variance using the F-test at the 5% level and second degree regression analysis. The dosage and time of application of nitrogen top-dressing did not affect seed weight or the germination of sweet corn seeds. An increase of the N top-dressing dosage, applied in the vegetative stage reduced the length of the aerial part, the root and the whole seedling