andRéa lúcia teixeiRa de Souza 5 RESUMO -Neste estudo foi descrito a biometria de frutos e de sementes de uma população de Hymenaea stigonocarpa var. stigonocarpa foi avaliado o efeito da massa de sementes na proporção e no tempo de germinação, sob condições de laboratório (câmara de germinação) e em viveiro, considerando como critérios de germinação a protrusão da raiz primária e a expansão de eófilos. Esta população de jatobá-do-cerrado apresentou uma grande variação no tamanho de frutos e de sementes. A massa das sementes variou entre 0,546 e 7,666 g e estas foram classificadas em pequenas, médias e grandes. Uma proporção maior de sementes classificadas como médias, emitiu a raiz primária em relação às grandes, enquanto as pequenas ocuparam posição intermediária. A massa de sementes não influencia a proporção de sementes que apresenta expansão de eófilos. As sementes grandes emitem a raiz primária mais rapidamente que as pequenas. O tempo médio da expansão de eófilos decresce com a redução da massa de sementes. Apesar das sementes médias e pequenas possuírem maior potencial para expor a raiz primária, estas apresentam maior taxa de mortalidade na transição entre as fases de protrusão da raiz primária e de expansão de eófilos.Termos para indexação: biometria, protrusão da raiz primária, expansão de eófilos. FRUIT AND SEED SIZE AND THEIR INFLUENCE ON THE GERMINATION OF Hymenaea stigonocarpa var. stigonocarpa Mart. ex Hayne (LEGUMINOSAE-CAESALPINOIDEAE)ABSTRACT -This study describes the biometry of the fruits and seeds of a population of Hymenaea stigonocarpa var. stigonocarpa. The effect of seed weight on the proportion and time of germination was evaluated under laboratory (BOD incubator) and nursery conditions, considering as criteria for germination, primary root protusion and eophylum expansion. This population of H. stigonocarpa var. stigonocarpa varied significantly in fruit and seed size with seed weights ranging between 0.546 and 7.666 g and classified as small, medium and large. A higher proportion of medium-sized seeds emitted the primary root compared to large seeds, whereas small seeds showed an intermediate pattern. However, seed weight did not influence the proportion of seeds that expanded the eophylum. The primary root of large seeds emerged faster than those of small

The successful establishment of trees in pastures may he related to species, seed size, and weed control treatments. This study experimentally evaluated the emergence, establishment after 2 years, and growth of individuals of 7 tree species with different seed sizes sowed under three weeding methods (no weeding, grasses clipped, and grasses removed). The experiment was carried out in a tropical abandoned pasture in Midwestern Brazil, dominated by the exotic invasive grass Urochloa brizantha. The effect of seed size on seedling emergence was significant and was more intense in the no weeding and weeding treatment plots than in grasses clipped. Furthermore, an increase in seed size resulted in an increase in the probability of establishment of tree species, although this pattern also differed among weeding treatments. The increase in seed size reflected negatively on tree growth in the absence of grasses, whereas in the presence of grasses there was an inverse relationship. The experimental results suggested that the use of seeds of different sizes for direct seeding in pastures is a possible strategy of Fabaceae tree species reintroduction in pastures within the Cerrado. Fabaceae species with seeds larger than 100 mg can establish in areas with no weeding, whereas species with seeds smaller than 50 mg can establish preferentially in areas with weeding, growing faster than larger ones. Thus, weeding strategies can determine the success of direct seeding of different species in restoration projects of tropical pastures.

Resumo -O objetivo deste trabalho foi avaliar a influência de tratamentos de superação da dormência de sementes sobre a taxa e o tempo de emergência de espécies arbóreas de Fabaceae, e sobre seu estabelecimento, quando reintroduzidas em pastagem, no Cerrado.

IV Alelopatia de duas espécies de braquiária em sementes de três espécies de estilosantesAllelopathy of two brachiaria species in seeds of three species of stylosanthes

-Tree establishment in pasture areas can be inhibited, at least in part, by exotic grasses allelopathy and this can represent an important limitation by changing the patterns of both germination and seedling growth of tree species. This study aims to evaluate the allelopathic potential of Urochloa brizantha and U. decumbens on germination, growth and metabolism of Guazuma ulmifolia seedlings. We performed bioassays evaluating the effect of the crude ethanol extract and semipurified fractions (hexane fraction, ethyl acetate fraction and ethanol-water fraction) of U. brizantha and U. decumbens using completely randomized design, with four concentrations (0, 250, 500, 1,000 mg L -1) and four replications. The variables analyzed were germination percentage, mean germination time, shoot and root growth, catalase and peroxidase activity, chlorophyll content and root respiration. The results showed that both grasses have an inhibitory effect on G. ulmifolia metabolism, affecting both germination and seedlings growth and inducting metabolic defense. Thus, these results show that the grass species evaluated have the potential to restrict the re-introduction of G. ulmifolia in pasture areas due to interference competition.Keywords: Guazuma ulmifolia, interference competition, exotic grasses, direct sowing, restoration, Urochloa. RESUMO -O estabelecimento

RESUMO -Nos últimos anos, com o lançamento de novas cultivares de estilosantes, o uso destas tem se expandido e, consequentemente, a venda de sementes com as devidas exigências de boletins de análises. Dentre as condições consideradas ideais para a germinação destaca-se a temperatura. Objetivou-se neste trabalho, avaliar a germinação de sementes de Stylosanthes capitata e S. macrocephala submetidas às temperaturas constantes de 20, 25, 30 e 35 ºC, e às temperaturas alternadas de 20-30 ºC, 20-35 ºC e 25-35 ºC. Conclui-se que para o teste de germinação de sementes de Stylosanthes capitata e S. macrocephala, deve-se utilizar as temperaturas alternadas de 20-30 ºC ou de 20-35 ºC ou a temperatura constante de 25 ºC.Termos para indexação: Stylosanthes capitata, Stylosanthes macrocephala, leguminosa. GERMINATION TEMPERATURE IN STYLOSANTHES SEEDSABSTRACT -In recent years, with the launching of new stylosanthes cultivars, there has been a consequent increase in seed sales which are accompanied by the necessary analysis report. Among the conditions considered ideal for germination is the temperature. The objective of this study was to evaluate the germination of Stylosanthes capitata and Stylosanthes macrocephala seeds at constant temperatures of 20, 25, 30 and 35 ºC, and alternating temperatures of 20-30 ºC, 20-35 ºC and 25-35 ºC. It was concluded that for the germination test of Stylosanthes capitata and S. macrocephala, the alternating temperatures of 20-30 ºC or 20-35 ºC or a constant temperature of 25 °C should be used.

No abstract

The application of chemical pesticides for the control of fungal diseases results in impacts on the environment and human health. The use of vegetal extracts with antifungal properties for the proper management of crops becomes a viable alternative, mainly for organic and family farming. The objective of this study was to carry out the phytochemical evaluation of Datura inoxia, evaluating its antifungal potential against the mycelial growth of Fusarium solani and Sclerotinia sclerotiorum. The extracts, aqueous and ethanolic, obtained from the leaves of the plant collected in areas of the municipality of Campo Grande, Mato Grosso do Sul, were submitted to phytochemical prospecting and quantification of flavonoids and total phenols. It was evaluated its antifungal activity at concentrations of 800, 1200, 1600, 2000, and 2400 μg 100 mL-1. Each concentration was separately incorporated into BDA agar, poured into Petri dishes, and inoculated with the mycelial disc of the fungus. The diameter of the colonies were measured daily. Two solutions were prepared as control, one containing the solvent added to PDA medium (ethanol solution), and another with only PDA medium (without D. inoxia extract, control). In both extracts were found the same diversity of secondary metabolites (nine classes). The ethanolic extract, a solvent of lower polarity than water, was more efficient in the extraction of these constituents. Alkaloids and phenolic compounds were the most frequent compounds (100%). In relation to antifungal activity, the ethanolic extract provided 100% inhibition of mycelial growth of Sclerotinia sclerotitorum in all concentrations, relative to the control. On the other hand, the growth of Fusarium solani was only negatively affected at the highest concentrations of 800 and 1200 μmL-1 100 mL-1. The antifungal potential of Datura inoxia was probably related to the abundance of alkaloids and phenolic compounds in its chemical constitution that negatively effects the development of the vegetative mycelium.