Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Botânica, 2008. / Submitted by Suelen Silva dos Santos (suelenunb@yahoo.com.br) on 2009-09-14T17:56:28Z
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2008_GiselleOliveiraPina.pdf: 6499098 bytes, checksum: c001bfcf0bff7d7c23fcaa943c94b1e8 (MD5) / Alelopatia é a influência de plantas sobre outros organismos por meio de compostos por elas produzidos e lançados no meio. Algumas espécies da família Myrtaceae apresentam evidências de propriedades alelopáticas. Eugenia dysenterica DC., conhecida como cagaita, é frequentemente encontrada no Cerrado sentido restrito. Os objetivos desse estudo foram quantificar os efeitos alelopáticos de extratos aquosos foliares de cagaita na germinação e no crescimento de gergelim (Sesamum indicum L.) e de rabanete (Raphanus sativus L.), e verificar se a atividade alelopática dos extratos tem interferência do pH e da secagem das folhas antes do preparo dos mesmos. Para tal, os extratos foram preparados a partir de folhas maduras frescas e secas. A secagem ocorreu em estufa (50 ºC /24h). Em ambos os casos as folhas foram trituradas e solubilizadas em água a 5% (p/v) com diluição para 1% e 3%. Os efeitos do pH do extrato foram verificados através de tratamentos com o pH original do extrato (4,7) e tratamentos com o pH ajustado para 7,0. Para a germinação, foram utilizadas placas de petri com 10 sementes de gergelim/rabanete contendo 6 mL dos extratos (suas diluições) e água como controle, com três repetições por tratamento. Houve acompanhamento diário por 5 dias. Para os experimentos de crescimento nos extratos, foram utilizadas sementes pré-germinadas em água. Após cinco dias as plântulas tiveram suas partes aérea e radicular medidas e características morfológicas registradas. Os experimentos foram conduzidos em câmaras de germinação a 25ºC (rabanete) e 30oC (gergelim), com fotoperíodo de 12h. Os resultados mostram que a germinabilidade e o tempo médio de germinação de ambas as espécies-alvo não foram afetados pelos extratos, independentemente do pH e da secagem ou não das folhas. Quanto ao crescimento, a parte radicular foi a mais afetada para as duas espécies, apresentando redução em seu comprimento 82% (gergelim) e 87% (rabanete), escurecimento radicular em todas as plântulas em contato com o extrato, redução do número de plântulas com pêlos radiculares (73% e 90% - gergelim e rabanete, respectivamente) e com raízes laterais (30% e 70% respectivamente). O ajuste do pH para 7,0 não alterou o potencial alelopático do extrato. O extrato proveniente de folhas secas promoveu maior efeito inibitório no crescimento radicular 85% (gergelim) e 86% (rabanete) que o de folhas frescas (69% e 80% respectivamente). ________________________________________________________________________________________________________________________ Abstract / Allelopathy is the influence that compounds produced by plants and released into the environment produces on other organisms. Some Myrtaceae’s species have shown some allelopathic property. Eugenia dysenterica DC., popular known as cagaita, is very common in the Cerrado sentido restrito. The objectives of this study were 1) to quantify the allelopathic effects of leaf aqueous extract of cagaita on the germination and growth of sesame (Sesamum indicum L.) and radish (Raphanus sativus L.) seedlings and 2) to verify if the allelopathic activity of the extracts are influenced by its pH and by the drying of the leaves before preparing them. Aqueous extracts were prepared using fresh and dry adult leaves. The leaves were dryed at 50º C for 24h. In both cases the leaves were grinded and dissolved in water at 5% (w/v) with posterior dilution to 1% and 3% for the experiments. The effects of pH of the extracts were verified through treatments keeping the original pH value (4,7) and treatments with pH adjusted to (7,0) with NaOH. To test the effects on germination, Petri dishes with 10 seeds of sesame/radish each containing 6 ml of the extracts (1 and 3%) were employed, water was the control. Three replications by treatment were conducted. Germinated seeds were counted everyday for up to five days. To test the effects on seedling growth, seeds previously germinated in water were employed. They were disposed in 15cm petri dishes with 10 mL of the extract to be tested. Water was the control. All the experiments were carried out in B.O.D. chambers at 25ºC (radish) and 30ºC (sesame), with photoperiod of 12h. After five days, the seedlings had their aerial and root parts measured and morphological characteristics were recorded. The results show that the germinability and the average time of germination of both targeted-species were not affected by the leaf extract of cagaita, irrespective of its pH and the drying of the leaves. However, the seedling growth was affected by the extracts. For both species the root parts showed to be more sensitive to the extracts than the shoot parts, showing a growth inhibition of about 82% (sesame) and 87% (radish), when compared to the growth in water. Both sesame and radish seedlings incubated in the extracts presented a reduction of the number of seedlings with root hairs (73% and 90% - sesame and radish, respectively) and with lateral roots (30% and 70% respectively). These effects were not affected by the pH adjustment. However, extracts prepared with dry leaves promoted a higher inhibitory effect on root growth 85% (sesame) and 86% (radish) than the fresh leaves one (69% and 80% respectivetly).
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.unb.br:10482/5475 |
| Date | 03 1900 |
| Creators | Pina, Giselle de Oliveira |
| Contributors | Pereira, Luiz Alfredo Rodrigues, Borghetti, Fabian |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UnB, instname:Universidade de Brasília, instacron:UNB |
| Rights | info:eu-repo/semantics/openAccess |
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