Departamento de Botânica

Allelopathic effects of aqueous extracts of Crinum americanum L.). In this paper we investigated the action of the allelopathic properties of aqueous extracts of Crinum americanum L. on the percentage and average time of germination and initial growth of Lactuca sativa L., Sesamum indicum L. and Raphanus sativus L. and of the weed species: Echinochloa crusgalli (L.) P. Beauv., Ipomoea grandifolia (Dammer) O'Donell and Bidens pilosa L. We prepared aqueous extracts from individuals of C. americanum from a blind estuary in Caraguatatuba, São Paulo and set the osmotic control with PEG 6000. We analyzed the germination data with Kruskal-Wallis and Dunn's post test, and the initial growth data with ANOVA and Tukey's post test. For all the tested species the result we found out was a decrease in the germination and in the initial growth and an improvement of germination average time. The osmotic control indicated little influence of osmolarity on the tests. We concluded that C. americanum has allelopathic potential over the tested species.

The competitive abilities of a given species are inversely proportional to its tolerance to environmental stress. Thus, in estuaries, vegetation is generally controlled by salinity and flooding in their lower limits, and by biotic drivers in their upper limits. Crinum americanum L. is vastly distributed over flooded regions of American seacoast, frequently associated with stressful habitats. We aimed to explain the role of hydrologic, edaphic, and biotic drivers in the distribution of this species on the Massaguaç u River estuary, Southeastern Brazil (23 • 37 20 S and 54 • 21 25 W). We sampled randomly 400 plots in the estuary, and registered covering of all species, the height of the C. americanum individuals, and the relative height of the plots. We collected soil samples from every five plots. We measured the estuary level daily for two years. We used Correspondence Analysis, Simple and Canonical, and graphic analysis. The salinity has explained the major part of the observed pattern, and the C. americanum population was positively related to it. The estuary level was also important. C. americanum has presented higher densities in intermediary flooding classes than in the extremes of the gradient. Species reduction in regions of low salinity or its absence has probably been due to the highly competitive environment, and not to the lack of salt per se.

Identification of species with allelopathic potential has been a target of researches aiming to use them to control crop weeds. Ipomoea cairica is considered a weed with allelopathic potential, which has already been reported. The goal of this study was to evaluate the allelopathic properties of leaf extracts from Ipomoea cairica on the germination and early development of four of the worst crop weeds in Brazil: Bidens pilosa L., Echinochloa crus-galli (L.) Beauv., Euphorbia heterophylla L. and Ipomoea grandifolia (Dammer) O´Donel. We tested the effects of leaf extracts, in four concentrations, on the germination and early development of these species. The extracts negatively affected the germination, early development and the morphology of all target species, and the phytotoxic effect was higher as the concentration of the extracts increased. The influence of the I. cairica extracts on germination, in addition to their effects on seedling development, made them more effective.

Potencial alelopático de macrófi tas aquáticas de um estuário cego 1 RESUMO (Potencial alelopático de macrófi tas aquáticas de um estuário cego). Macrófi tas aquáticas representam uma das comunidades mais produtivas e através de sua atividade metabólica são capazes de produzir grandes interferências no ambiente. As interações alelopáticas são aparentemente aumentadas sob condições de estresse biótico e abiótico e podem existir em estuários devido à competição, variações de salinidade e outros fatores. O objetivo desse trabalho foi avaliar as propriedades alelopáticas de extratos aquosos foliares de 25 espécies de macrófi tas aquáticas de um estuário cego. Testamos os efeitos dos extratos foliares em quatro concentrações sobre a germinação de alface. Ordenamos e comparamos as espécies doadoras de acordo com a dose reposta sobre a variedade de tratamentos a partir de valores únicos de índices alelopáticos. Onze das 25 espécies diminuíram a porcentagem de germinação, todas diminuíram a velocidade de germinação e aumentaram a entropia informacional de germinação das sementes da espécie alvo em pelo menos uma das concentrações testadas. Crinum americanum L., Sagittaria montevidensis Cham. & Schl. e Ipomoea cairica (L) Sweet apresentaram os maiores valores de índice alelopático. Em geral, as menores porcentagens de germinação coincidiram com as menores velocidades e maiores entropias informacionais de germinação das sementes de alface, mostrando um conjunto de alterações ocorrendo simultaneamente com o aumento da concentração dos extratos.

Potencial alelopático de macrófi tas aquáticas de um estuário cego 1 RESUMO (Potencial alelopático de macrófi tas aquáticas de um estuário cego). Macrófi tas aquáticas representam uma das comunidades mais produtivas e através de sua atividade metabólica são capazes de produzir grandes interferências no ambiente. As interações alelopáticas são aparentemente aumentadas sob condições de estresse biótico e abiótico e podem existir em estuários devido à competição, variações de salinidade e outros fatores. O objetivo desse trabalho foi avaliar as propriedades alelopáticas de extratos aquosos foliares de 25 espécies de macrófi tas aquáticas de um estuário cego. Testamos os efeitos dos extratos foliares em quatro concentrações sobre a germinação de alface. Ordenamos e comparamos as espécies doadoras de acordo com a dose reposta sobre a variedade de tratamentos a partir de valores únicos de índices alelopáticos. Onze das 25 espécies diminuíram a porcentagem de germinação, todas diminuíram a velocidade de germinação e aumentaram a entropia informacional de germinação das sementes da espécie alvo em pelo menos uma das concentrações testadas. Crinum americanum L., Sagittaria montevidensis Cham. & Schl. e Ipomoea cairica (L) Sweet apresentaram os maiores valores de índice alelopático. Em geral, as menores porcentagens de germinação coincidiram com as menores velocidades e maiores entropias informacionais de germinação das sementes de alface, mostrando um conjunto de alterações ocorrendo simultaneamente com o aumento da concentração dos extratos.

Resumo -O objetivo deste trabalho foi comparar uma população de leveduras do filoplano de lírio de um sistema convencional de cultivo com outra de sistema integrado, além de avaliar o antagonismo da levedura Sporidiobolus pararoseus a Botrytis cinerea. A comunidade de leveduras foi estimada pelo método da queda dos balistoporos nos terços inferior, médio e superior das plantas, bem como nas faces adaxial e abaxial das folhas. Nos discos de folhas de plantas do sistema integrado, foi alta a presença da população de leveduras, tendo sido maior na face adaxial das folhas do terço médio das plantas. Para avaliação do antagonismo, foram aplicadas aos discos de folhas as concentrações de 10 5 , 10 6 e 10 7 células mL -1 da levedura, em três períodos de inoculação: 24 horas antes; simultânea a; e 24 horas após a inoculação de 10 4 esporos mL -1 de B. cinerea. A incidência, a percentagem de área de discos colonizados e a esporulação de B. cinerea foram avaliadas por meio de diagrama de notas, a partir do quarto dia após a inoculação. Todas as concentrações da levedura reduziram a esporulação de B. cinerea nos discos de folha, em comparação à testemunha, e a concentração de 10 7 esporos mL -1 foi a mais eficiente.

Allelopathic substances can be used to develop weed control alternatives based on natural products. The objective of this study was to compare the phytotoxic activity of aqueous leaf extracts of Rapanea umbellata with the toxicity of a synthetic herbicide on the germination and growth of weed species. The weeds species barnyard grass (Echinochloa crus-galli), wild poinsettia (Euphorbia heterophylla) and morning glory (Ipomoea grandifolia) were used. The effects of the aqueous leaf extract of R. umbellata at concentrations of 10% and 5% (g mL -1 ) were compared to the control (distilled water) and to the synthetic herbicide oxyfluorfen. The average weed germination time was significantly lower (p < 0.05) in control than in extract and herbicide treatments. The herbicide had more significant effects than the extract on the initial growth of the aerial part. However, the initial growth of the root part was significantly more affected by the leaf extract than by the herbicide. The extract also caused many disorders in weed root anatomy. Therefore, the leaf aqueous extract of R. umbellata showed important results that indicate that it should be bioprospected and that its allelochemicals should be purified for the discovery of natural-origin herbicides.

Tithonia diversifolia (Mexican sunflower) is a dominant plant of the Asteraceae family, which suggests it produces allelochemicals that interfere with the development of surrounding plants. The study described herein was conducted to identify the compounds that have phytotoxic activity in T. diversifolia extracts. Ethyl acetate extracts of the leaves, stems, and roots showed significant inhibition of wheat coleoptile growth, and the leaf extract had similar inhibitory effects to a commercial herbicide. Fourteen compounds, 12 of which were sesquiterpene lactones, have been isolated. Two sesquiterpene lactones are reported for the first time and were isolated as an inseparable mixture of 8β-O-(2-methylbutyroyl)tirotundin (4) and 8β-O-(isovaleroyl)tirotundin ( ). Their structures were determined by spectroscopic analysis, including NMR techniques and mass spectrometry. The sesquiterpene lactones 1β-methoxydiversifolin (6), tagitinin A (7), and tagitinin C (8) were the major products identified. These compounds were active on etiolated wheat coleoptiles, seed germination, and the growth of STS and weeds. The phytotoxic activity shown by these sesquiterpene lactones indicates that they are the compounds responsible for the activity exhibited by the initial extracts.

Allelopathic substances can be used to develop weed control alternatives based on natural products. The objective of this study was to compare the phytotoxic activity of aqueous leaf extracts of Rapanea umbellata with the toxicity of a synthetic herbicide on the germination and growth of weed species. The weeds species barnyard grass (Echinochloa crus-galli), wild poinsettia (Euphorbia heterophylla) and morning glory (Ipomoea grandifolia) were used. The effects of the aqueous leaf extract of R. umbellata at concentrations of 10% and 5% (g mL-1) were compared to the control (distilled water) and to the synthetic herbicide oxyfluorfen. The average weed germination time was significantly lower (p < 0.05) in control than in extract and herbicide treatments. The herbicide had more significant effects than the extract on the initial growth of the aerial part. However, the initial growth of the root part was significantly more affected by the leaf extract than by the herbicide. The extract also caused many disorders in weed root anatomy. Therefore, the leaf aqueous extract of R. umbellata showed important results that indicate that it should be bioprospected and that its allelochemicals should be purified for the discovery of natural-origin herbicides.

RESUMO-Este trabalho avaliou o potencial alelopático de extratos foliares e radiculares de Lafoensia glyptocarpa Koehne sobre a germinação de sementes e o crescimento de plântulas e de células do metaxilema de gergelim (Sesamum indicum L.). A partir dos resultados, verifi cou-se que os extratos de folhas e raízes de L. glyptocarpa causaram alterações na germinação das sementes e no crescimento das plântulas de gergelim, além de alterações na raiz primária e diminuição no tamanho e número de células do metaxilema. Foram também obtidos extratos foliares com hexano, diclorometano, acetato de etila, acetona e metanol, e testados sobre o desenvolvimento de coleóptilos de trigo, sendo que os quatro últimos apresentaram atividade. Com o sub-fracionamento do extrato de acetato de etila, que se apresentou como o mais promissor, cessou a atividade inibitória para as sub-frações, sendo posteriormente verifi cada a presença de sinergismo entre elas. Palavras-chave: alelopatia; Lafoensia glyptocarpa; Sesamum indicum, sinergismo ABSTRACT-Allelopathic effects of Lafoensia glyptocarpa Koehne on Sesamum indicum L. and on the growth of Triticum aestivum L. coleoptiles. This study evaluated the allelopathic potential of leaf and root extracts of Lafoensia glyptocarpa Koehne on seed germination and the growth of seedlings and sesame (Sesamum indicum L.) metaxylem cells. We found that the leaf and root extracts of L. glyptocarpa changed in sesame seed germination and seedling growth, as well as changes in the primary root and decreased size and number of metaxylem cells. Leaf extracts were also obtained with hexane, dichloromethane, ethyl acetate, acetone, and methanol, and tested when developing wheat coleoptiles, and the last four showed activity. By subfractioning the ethyl acetate extract, which was the most promising, inhibitory activity ceased for subfractions, and the presence of synergism was subsequently found between them.