Addendum in pocket. Biblography: leaves 162-173. Phytophagous sucking insects, aphids in particular, are common pests of plants. These insects secrete salivary enzymes into their food material. One plant defence mechanism is the induction and/or accumulation of deterrent phytochemicals. In the present study, a model enzyme system was chosen to mimic the oxidative activity of insect saliva. Isolation and sructural identification of the products of plant allelochemicals was achieved for several substrates. Insects were also exposed to individual plant chemicals in feeding "choice" tests. Preliminary examinations suggest that plants containing increased levels of phenolic allelochemicals show correlated increases in resistance to attack by aphids.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Addendum in pocket. / Biblography: leaves 162-173. / v, 177, [5] leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Phytophagous sucking insects, aphids in particular, are common pests of plants. These insects secrete salivary enzymes into their food material. One plant defence mechanism is the induction and/or accumulation of deterrent phytochemicals. In the present study, a model enzyme system was chosen to mimic the oxidative activity of insect saliva. Isolation and sructural identification of the products of plant allelochemicals was achieved for several substrates. Insects were also exposed to individual plant chemicals in feeding "choice" tests. Preliminary examinations suggest that plants containing increased levels of phenolic allelochemicals show correlated increases in resistance to attack by aphids. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1996

Thesis (Ph. D.)--University of Montana, 2007. / Title from title screen. Description based on contents viewed Oct. 9, 2008. Includes bibliographical references.

Made available in DSpace on 2016-06-02T19:31:38Z (GMT). No. of bitstreams: 1 DissDCB.pdf: 1626871 bytes, checksum: d14e418a437d0b20300f24074864567c (MD5) Previous issue date: 2007-06-13 / The present study objected to appraise in vitro the kind of interference that is produced by addicion of leaves extracts Brachiaria decumbens Stapf and Melinis minutiflora Beauv. (exotic species, alien weeds) collected in raining season (12/01/2006) and dry season (10/08/2006) over germination and initial development of Lactuca sativa L. (bioindicator species) and Dalbergia miscolobium Benth. (native species of savanna). It were verified also that pH and osmotic potencial of both B. decumbens and M. minutiflora extracts did not cause interference in seed germination indices. The germination of D. miscolobium was not affected by leaves extracts obtained of material collected in dry season and raining season. The germination speed was more sensitive to action of extracts than germination percentage of L. sativa. The total length of the seedlings was reduced in practically all treatments when, compared with the control group, however significative statistical differences were observed just in above-ground part of the seedlings of L. sativa treated with leaves extracts of B. decumbens collected in dry season. The L. sativa root was stimulated when leaves extracts of M. minutiflora collected in dry season was added in Petri dishes. For seedlings of D. miscolobium the leaves extracts of B. decumbens collected in dry season decreased the length of the above-ground part and the root, and the same was observed for leaves extracts of M. minutiflora collected in the raining season. Anatomy studies of root-tip cells carried of D. miscolobium e L. sativa showed that the extracts of B. decumbens e M. minutiflora cause damage on the root cells of seedlings with different intensities, but the root cells of D. miscolobium, showed alterations most emphasized. / O presente estudo teve por objetivo avaliar in vitro qual o tipo de interferência é produzido pela adição de extratos de folhas de Brachiaria decumbens Stapf e Melinis minutiflora Beauv (espécies exóticas, invasoras do cerrado), coletadas na estação chuvosa e na estação seca sobre a germinação e o desenvolvimento inicial de Lactuca sativa L. (espécie bioindicadora) e Dalbergia miscolobium Benth. (espécie nativa do cerrado). Foi verificado também que o pH e o potencial osmótico dos extratos de B. decumbens e M. minutiflora não causaram interferência nos índices de germinação das sementes. A germinação de D. miscolobium não foi afetada pelos extratos foliares obtidos de material coletados nas estações seca e chuvosa. A velocidade de germinação foi mais sensível à ação dos extratos do que a porcentagem de germinação de L. sativa. O comprimento total das plântulas foi reduzido em praticamente todos os tratamentos quando, comparados ao grupo controle, contudo, diferenças estatisticamente significativas foram observadas apenas na parte aérea das plântulas de L. sativa tratadas com extratos de folhas de B. decumbens coletadas na estação seca. Houve estímulo do crescimento radicular de L. sativa quando extrato de folhas de M. minutiflora colhidas na estação seca foi adicionado ao meio. Para as plântulas de D. miscolobium o extrato de folhas de B. decumbens colhidas na estação seca reduziu o comprimento da parte aérea e da raiz, sendo o mesmo fato observado com o uso de extrato de M. minutiflora da estação chuvosa. Estudos anatômicos de tecidos meristemáticos das raízes de D. miscolobium e L. sativa evidenciaram que os extratos de B. decumbens e M. minutiflora provocaram danos às células das raízes destas plântulas em diferentes intensidades, mas as células das raízes de D. miscolobium, exibiram alterações mais acentuadas.

A alelopatia, na qual uma espécie causa efeitos negativos sobre outra através da liberação de substâncias químicas, é um fenômeno que pode afetar comunidades vegetais. Em alguns casos, o estabelecimento de arbustos aromáticos em formações densas, com apenas poucas espécies ocorrendo em suas proximidades, é um padrão que tem sido relacionado aos efeitos fitotóxicos dos voláteis que os mesmos liberam. Em campos dos sul do Brasil, esse padrão de estabelecimento frequentemente ocorre para as espécies arbustivas aromáticas Heterothalamus psiadioides Less e Baccharis patens Baker, indicando a possibilidade de alelopatia. Dessa forma, o presente estudo teve como objetivo determinar se H. psiadioides e B. patens são fitotóxicas e se isso implica em efeitos negativos sobre a comunidade vegetal na qual os arbustos ocorrem. Em ensaios em laboratório, os efeitos dos voláteis liberados diretamente das folhas frescas e secas de H. psiadioides e B. patens foram testados sobre a germinação e o crescimento das plantas-alvo alface e cebola nas quatro estações do ano. Em um estudo em campo, foram avaliadas cobertura e biomassa vegetal, número de mudas, diversidade, riqueza, e variáveis de estrutura da vegetação no entorno de ambas as espécies arbustivas e onde não havia arbustos. Nos bioensaios, os voláteis de H. psiadioides e B. patens causaram inibição na porcentagem e velocidade de germinação e redução no tamanho da raiz e da parte aérea das plantas-alvo, sendo que folhas frescas apresentaram maior fitotoxidez. Esses parâmetros foram mais afetados por H. psiadioides que por B. patens em todas as estações, e os efeitos de ambas foram menores no verão. Em relação à investigação em campo, que objetivou avaliar os efeitos da espécie muito fitotóxica H. psiadioides sobre a comunidade vegetal, não foram observadas evidências de alelopatia. Houve maior riqueza e diversidade próximo a H. psiadioides, devido à menor cobertura de gramíneas dominantes. Variáveis de estrutura da vegetação e intensidade de luz explicaram os padrões observados de forma mais conclusiva que alelopatia. Esse estudo sugere que o potencial alelopático de plantas pode ser superestimado em bioensaios e que estudos em campo são necessários para demonstrar se efeitos alelopáticos são realmente relevantes em comunidades vegetais. Ainda, o trabalho ressalta a importância de conduzir estudos mais realistas em laboratório e de utilizar controles em estudos em campo. / Allelopathy, in which a species causes negative effects on another through the release of chemical substances, is a phenomenon that may affect plant communities. In some cases, the establishment of aromatic shrubs in dense stands, with few other species occurring in their surroundings, has been related to the phytotoxic effects of volatiles released by these shrubs. In South Brazilian grasslands, this pattern of establishment often occurs for the aromatic shrub species Heterothalamus psiadioides Less and Baccharis patens Baker, indicating the possibility of allelopathy. Thus, this study aimed to determine if H. psiadioides and B. patens are phytotoxic and if this implicates in negative effects on the plant community in which the shrubs occur. In laboratory assays, the effects of the volatiles released directly from fresh and dry leaves of H. psiadioides and B. patens on germination and growth of the target plants lettuce and onion were evaluated in four seasons. A field study was carried out, in which vegetation cover and biomass, number of seedlings, diversity, richness, and variables of vegetation structure were evaluated in the surroundings of both species and where there were not shrubs. In the bioassays, H. psiadioides and B. patens volatiles inhibited the germination rate and speed of germination and reduced the root and shoot length of the target plants, with fresh leaves showing higher phytotoxicity. These parameters were more strongly affected by H. psiadioides than by B. patens in all seasons, and effects of the both shrubs were lower in summer. In relation to the field investigation that aimed to quantify the effects of the highly phytotoxic H. psiadioides on the plant community, no evidences of allelopathy were found. Richness and diversity were higher near H. psiadioides, due to lower cover of dominant grasses. Variables of vegetation structure and light intensity explained vegetation patterns more conclusively than allelopathy. This study emphasizes that the allelopathic potential of plants can be overestimated in bioassays, and that field studies are necessary to elucidate if allelopathic effects are in fact significant in plant communities. Still, the relevance of conducting more realistic laboratory studies and of using controls in field studies is highlighted.

The alien invader plant Parthenium hysterophorus is a Category 1 weed in South Africa, where it poses a serious threat to indigenous vegetation in particular, and to biodiversity in general. In addition to its competitive ability, it is hypothesized that the successful invasiveness of P. hysterophorus is linked to the allelopathic potential of the plant. One compound in particular, parthenin, is alleged to play a major role in this allelopathic potential. Interference between P. hysterophorus and three indigenous grass species (Eragrostis curvula, Panicum maximum, Digitaria eriantha) was investigated on a site with a natural parthenium infestation at Skukuza, Kruger National Park. The trial was conducted over two growing seasons on exclosure plots which eliminated mammal herbivory. P. maximum displayed best overall performance and was eventually able to completely overwhelm P. hysterophorus. Eragrostis curvula and D. eriantha grew more favourably in the second season after becoming better established but were clearly not well adapted to the trial conditions. Although P. maximum was the supreme interferer, all grasses were able to significantly interfere with P. hysterophorus growth in the second season. The ability of P. maximum to interfere with P. hysterophorus growth so efficiently that it caused mortalities of the latter species, indicates that P. maximum exhibits high potential for use as an antagonistic species in an integrated control programme. An investigation on the production dynamics of parthenin in the leaves of P. hysterophorus indicated that high levels of this compound are produced and maintained in the plant up until senescence. The high resource allocation priority of the plant towards this secondary metabolite even in the final growth stages may indicate the use of residual allelopathy to inhibit or impede the recruitment of other species. Studies on the persistence of parthenin in soil revealed that parthenin is readily degraded in soil and that microbial degradation appears to play a predominant role. Significant differences between parthenin disappearance-time half-life (DT50) values were observed in soils incubated at different temperatures and in soils with different textures. Exposure of the three grass species to pure parthenin showed that, in terms of their early development, the order of sensitivity of the grasses was: Panicum maximum>Digitaria eriantha>Eragrostis curvula. It may therefore prove challenging to establish P. maximum from seed in P. hysterophorus stands during the execution of an integrated control programme due to the sensitivity of this grass species to parthenin. From the research findings it appears possible that P. hysterophorus can inhibit or impede the recruitment of indigenous vegetation under natural conditions. At least one mechanism through which this alien species can exert its negative influence on other plant species is the production and release of parthenin. / Dissertation (MSc (Agric) Agronomy)--University of Pretoria, 2007. / Plant Production and Soil Science / unrestricted

A alelopatia, na qual uma espécie causa efeitos negativos sobre outra através da liberação de substâncias químicas, é um fenômeno que pode afetar comunidades vegetais. Em alguns casos, o estabelecimento de arbustos aromáticos em formações densas, com apenas poucas espécies ocorrendo em suas proximidades, é um padrão que tem sido relacionado aos efeitos fitotóxicos dos voláteis que os mesmos liberam. Em campos dos sul do Brasil, esse padrão de estabelecimento frequentemente ocorre para as espécies arbustivas aromáticas Heterothalamus psiadioides Less e Baccharis patens Baker, indicando a possibilidade de alelopatia. Dessa forma, o presente estudo teve como objetivo determinar se H. psiadioides e B. patens são fitotóxicas e se isso implica em efeitos negativos sobre a comunidade vegetal na qual os arbustos ocorrem. Em ensaios em laboratório, os efeitos dos voláteis liberados diretamente das folhas frescas e secas de H. psiadioides e B. patens foram testados sobre a germinação e o crescimento das plantas-alvo alface e cebola nas quatro estações do ano. Em um estudo em campo, foram avaliadas cobertura e biomassa vegetal, número de mudas, diversidade, riqueza, e variáveis de estrutura da vegetação no entorno de ambas as espécies arbustivas e onde não havia arbustos. Nos bioensaios, os voláteis de H. psiadioides e B. patens causaram inibição na porcentagem e velocidade de germinação e redução no tamanho da raiz e da parte aérea das plantas-alvo, sendo que folhas frescas apresentaram maior fitotoxidez. Esses parâmetros foram mais afetados por H. psiadioides que por B. patens em todas as estações, e os efeitos de ambas foram menores no verão. Em relação à investigação em campo, que objetivou avaliar os efeitos da espécie muito fitotóxica H. psiadioides sobre a comunidade vegetal, não foram observadas evidências de alelopatia. Houve maior riqueza e diversidade próximo a H. psiadioides, devido à menor cobertura de gramíneas dominantes. Variáveis de estrutura da vegetação e intensidade de luz explicaram os padrões observados de forma mais conclusiva que alelopatia. Esse estudo sugere que o potencial alelopático de plantas pode ser superestimado em bioensaios e que estudos em campo são necessários para demonstrar se efeitos alelopáticos são realmente relevantes em comunidades vegetais. Ainda, o trabalho ressalta a importância de conduzir estudos mais realistas em laboratório e de utilizar controles em estudos em campo. / Allelopathy, in which a species causes negative effects on another through the release of chemical substances, is a phenomenon that may affect plant communities. In some cases, the establishment of aromatic shrubs in dense stands, with few other species occurring in their surroundings, has been related to the phytotoxic effects of volatiles released by these shrubs. In South Brazilian grasslands, this pattern of establishment often occurs for the aromatic shrub species Heterothalamus psiadioides Less and Baccharis patens Baker, indicating the possibility of allelopathy. Thus, this study aimed to determine if H. psiadioides and B. patens are phytotoxic and if this implicates in negative effects on the plant community in which the shrubs occur. In laboratory assays, the effects of the volatiles released directly from fresh and dry leaves of H. psiadioides and B. patens on germination and growth of the target plants lettuce and onion were evaluated in four seasons. A field study was carried out, in which vegetation cover and biomass, number of seedlings, diversity, richness, and variables of vegetation structure were evaluated in the surroundings of both species and where there were not shrubs. In the bioassays, H. psiadioides and B. patens volatiles inhibited the germination rate and speed of germination and reduced the root and shoot length of the target plants, with fresh leaves showing higher phytotoxicity. These parameters were more strongly affected by H. psiadioides than by B. patens in all seasons, and effects of the both shrubs were lower in summer. In relation to the field investigation that aimed to quantify the effects of the highly phytotoxic H. psiadioides on the plant community, no evidences of allelopathy were found. Richness and diversity were higher near H. psiadioides, due to lower cover of dominant grasses. Variables of vegetation structure and light intensity explained vegetation patterns more conclusively than allelopathy. This study emphasizes that the allelopathic potential of plants can be overestimated in bioassays, and that field studies are necessary to elucidate if allelopathic effects are in fact significant in plant communities. Still, the relevance of conducting more realistic laboratory studies and of using controls in field studies is highlighted.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Species of the genus Psychotria L. are used in Brazilian folk medicine as tea, however, their indiscriminate and uncontrolled can cause more harm than good to health. It is important to understand these plants, from their cellular levels to the action on living organisms, and for monitoring toxic substances allelopathic bioassays are widely used with plant species as the target organisms. This study aimed to evaluate the genotoxic, antiproliferative and antimutagenic potential of infusions of Psychotria brachypoda (Muell. Arg.) Briton and Psychotria birotula Smith & Downs on the cell cycle of Allium cepa L., in addition to analyzing the antiproliferative and genotoxic potential on the germination on seeds and cell cycle of Eruca sativa Mill. For this, dried leaves were used to prepare extracts in two concentrations for each species: 5g.L-1 and 20g.L-1, using distilled water as a negative control and glyphosate 3% as a positive control. For the study, antiproliferative on the germination (allelopathic potential) variables were analyzed: total number of germinated seeds, seedling root length, index of germination rate, and germination percentage. To evaluate the genotoxic, antiproliferative and antimutagenic potential, both for the test with A. cepa and with E. sativa were analyzed mitotic index and the number of chromosomal alterations. The extracts of P. brachypoda have no genotoxic potential, though the extracts of P. birotula possess genotoxic potential on the A. cepa cell cycle and the extracts of P. brachypoda and P. birotula showed no antimutagenic potential, no entanto, apresentaram genotoxic, and antiproliferative potential on the germination and cell cycle E. sativa. / Espécies do gênero Psychotria L. são utilizadas na medicina popular brasileira, na forma de chá, porém, o uso indiscriminado e sem controle pode causar mais danos à saúde do que benefícios, sendo importante o conhecimento dessas plantas, desde os níveis celulares bem como a ação sobre os organismos vivos. Para monitorar substâncias tóxicas e alelopáticas são muito utilizados ensaios biológicos com espécies vegetais como organismos alvo. O presente trabalho objetivou avaliar o potencial antiproliferativo, genotóxico e antimutagênico de extratos das folhas de Psychotria brachypoda (Müll. Arg.) Briton e Psychotria birotula Smith & Downs sobre o ciclo celular de Allium cepa L., além do potencial antiproliferativo e genotóxico sobre a germinação de sementes e ciclo celular de Eruca sativa Mill. Para isto, foram utilizadas folhas secas para preparar extratos em duas concentrações para cada espécie: 5g.L-1 e 20g.L-1, sendo utilizada água destilada como controle negativo e o glifosato 3% como controle positivo. Para a análise do potencial antiproliferativo sobre a germinação (potencial alelopático) analisou-se as variáveis: número total de sementes germinadas, comprimento das raízes das plântulas, índice da velocidade de germinação e porcentagem de germinação. Para avaliação do potencial genotóxico, antiproliferativo e antimutagênico sobre o ciclo celular, tanto para o teste com A. cepa quanto com E. sativa foram analisados o índice mitótico e o número de alterações cromossômicas. Os extratos de P. brachypoda não apresentaram potencial genotóxico, já os extratos de P. birotula foram genotóxicos sobre o ciclo celular de A. cepa. Os extratos de P. brachypoda e P. birotula não apresentaram potencial antimutagênico, no entanto, demonstraram potencial antiproliferativo genotóxico sobre germinação e ciclo celular de E. sativa.