Thesis (B.A.(Hons.)) -- University of Adelaide, 1977. / Includes bibliographical references (p. 31-32).

No description available.

No description available.

Inoculation experiments were carried out to determine the relation between bark moisture level of certain host species and their susceptibility to facultative parasites. In these experiments, cuttings of 1-to 3-year old host material and the mycelial mat of the pathogens contained in an agar cylinder were used. In the first instance, fungi that were known or found in association with bark lesions were considered: these were Cryptodiaporthe salicella (Fr.) Petrak on Salix scouleriana Barratt (Scouler willow), Dactylosporium sp. and Fusarium sp. on Acer macrophyllum Pursh. (broadleaf maple, Libertella sp. on Cornus stolonifera (Michx.) var. occidentalis (T. and G.) C. L. Hitchc. (western dogwood), Melanconis sp. on Alnus rubra Bong. (red alder). The results demonstrated that fungi normally associated with lesions of living host material proved to be pathogenic when the relative turgidity of the host bark was lowered from the field level of above 80 per cent to the range of 69 to 77 per cent. Secondly, an attempt was made to determine if correlation existed between bark moisture level and canker development by fungi not known, and not found to occur in association with lesions of some hosts. The following fungi and hosts were considered: C. salicella on red alder (Alnus rubra Bong), trembling aspen (Populus tremuloides Michx.), bitter cherry (Prunus emarginata Dougl.), black cottonwood (Populus trichocarpa Torrey and Gray), western dogwood (Cornus stolonifera var. occidentalis), and on broadleaf maple (Acer macrophyllum Pursh.); Fusarium sp. on red alder, bitter cherry, western dogwood, and on Scouler willow; Libertella sp. on red alder, bitter cherry, broadleaf maple, and on Scouler willow; Melanconis sp. on bitter cherry, western dogwood, broadleaf maple and on Scouler willow. It was shown that all of these parasites extended their host ranges, to varying extent when the bark moisture level was reduced to levels within the range of 69 to 77 per cent, or in some instances to the range of 41 to 67 per cent of saturation. Cuttings with as low bark moisture levels as 41 per cent appeared to be viable as indicated by the production of roots and (or) shoots. / Science, Faculty of / Botany, Department of / Graduate

3 pp. / Originally published: 2003 / Dwarf mistletoes are parasitic flowering plants that grow within host plants for about two years before producing characteristic yellow to orange or green to brown leafless aerial shoots on the outside of infected host tissue. They occur only on conifers in the pine family in Arizona and are usually host specific. This article gives information about the disease cycle, the symptoms and prevention and control methods for dwarf mistletoes.

Foraging theory predicts active responses by organisms upon encounter with a resource, as opposed to the passive responses of differential survivorship and growth. Stems of the parasitic plant Cuscuta subinclusa invest in resource acquisition (coil) relative to host quality in a way predicted by the marginal value theorem (MVT) in that: (1) stem coiling, the necessary antecedent and determinant of resource uptake, precedes exploitation of host materials; and (2) mean coiling on a host species is proportional to: (a) mean growth/haustorium, (b) mean biomass accumulation over the season, and (c) mean parasite growth/host individual. Coiling is correlated with growth/host individual for the 5 native host species examined, but not when a non-native species is added to the model, suggesting coiling response is a result of natural selection. Preliminary evidence indicates that coiling in C. subinclusa is induced by host bark chemicals. Resource-poor stems of C. subinclusa are more likely to coil, and coil more, than resource-rich stems, thus nutritional state of the parasite as well as host value affects foraging responses. Evidence from other experiments suggests that the costs of growth, or "search costs", may affect host acceptability. When water is readily available, transplanted C. subinclusa stems are less likely to coil on branches of Platanus racemosa. During the dry season, when cellular expansion is difficult, all p. racemosa branches were coiled upon. Large parasites are more likely to over-winter and set seed a second season, and parasites that start from over-wintered tissue are significantly larger at flowering than are those that have started from seed. Seed set is correlated with parasite size, thus linking foraging response and fitness of the plant. C. subinclusa's foraging response does not, however, predict population level patterns of host use. The principal determinant of host use by C. subinclusa is average proximity of a species to Malosma laurina. Parasite individuals infest many host species each season, but initially establish, set most seed, and over-winter only on M. laurina. Individual response of C. subinclusa contributes to the model of host use only after proximity to M. laurina is accounted for, suggesting that mechanisms maximizing exploitation of a host take effect after contact between host and parasite.

Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry, March 2000. / Includes bibliographical references. Also available on the Internet.

No description available.

Plantas parasitas são aquelas que retiram os recursos necessários para a sua sobrevivência de outras plantas (hospedeiras) por meio de uma estrutura denominada haustório, que permite que a parasita se conecte ao sistema vascular da hospedeira. As plantas podem responder ao ataque parasita ativando alguns mecanismos de defesa, dentre eles, a produção de substâncias fenólicas. Os viscos constituem um grupo de plantas parasitas aéreas pertencentes a Santalales que podem ser divididos em viscos holoparasitas ou hemiparasitas. Alguns gêneros de viscos são de importância econômica, dentre eles, Phoradendron, um gênero de visco hemiparasita. Esse trabalho teve como objetivos determinar os conteúdos de taninos, flavonoides, fenilpropanoides, carboidratos solúveis, amido, lipídeos, a razão carbono/nitrogênio e avaliar como a relação parasítica afeta o metabolismo das espécies envolvidas. Para tanto, coletou−se no município de Campanha (MG) folhas e ramos de seis indivíduos não parasitados de Tapirira guianensis (FT e RT) e, a partir de nove indivíduos parasitados de T. guianensis, foram coletados ramos e folhas de Phoradendron crassifolium (FP e RP), ramos não infestados da hospedeira e suas folhas (RNI e FRNI) e ramos infestados de T. guianensis e suas folhas (RI e FRI), sendo que ramos infestados foram divididos em região proximal, galha e distal (RPRI, RGRI e RDRI). Como principais resultados estão o aumento no teor de proantocianidinas e de carboidratos solúveis em FRNI e FRI em relação a FT. Ramos infestados sofreram redução nos conteúdos de carboidratos solúveis, amido, lipídeos, nitrogênio e substâncias fenólicas, exceto na região da galha (RGRI) em que aumentos de amido e flavonoides foram verificados. Observou-se ainda que RNI parece ter sofrido um acúmulo de substâncias fenólicas. O conjunto dos resultados obtidos mostra que P. crassifolium afeta o metabolismo primário e o secundário de T. guianensis, com influência mais pronunciada nos ramos do que nas folhas da hospedeira. Pode−se sugerir que a parasita obtêm nitrogênio e carboidratos solúveis de sua hospedeira e que pode ocorrer uma possível realocação de carbono para crescimento, desenvolvimento, manutenção e, ainda, defesa de ramos ainda não infestados. Além disso, sugere−se que o acúmulo de fenólicos em ramos não infestados (RNI) possa ser um mecanismo de defesa usado pela hospedeira com o objetivo de evitar, ou mesmo diminuir, novas infestações em ramos ainda não parasitados. / Parasitic plants are those that withdraw necessary resources for its survival from other plants (hosts) through a structure so-called haustorium which enables the parasite to connect to the host\'s vascular system. Plants can respond to the parasite attack activating some defense mechanisms, including the production of phenolic compounds. Mistletoes are a group of stem parasitic plants belonging to Santalales that can be grouped into holoparasite or hemiparasite mistletoes. Some mistletoes genera are of economic importance among them Phoradendron, a hemiparasite mistletoe. This study aimed to determine the contents of tannins, flavonoids, phenylpropanoids, soluble carbohydrates, starch, lipids, the carbon⁄nitrogen ratio and evaluate how the parasitic relationship affects the metabolism of the involved species. Were collected in Camapanha (MG) leaves and branches from six non−parasitized individuals of Tapirira guianensis, host plant (LT and BT). From nine parasitized individuals of T. guianensis were collected branches and leaves of Phoradendon crassifolium, the parasitic plant (LP and BP), non-infested host branches and their leaves (NIHB and NIHB-L) and infested branches and their leaves (IHB and IHB-L). Infested branches of T. guianensis were divided into proximal, gall, and distal regions (IHB-P, IHB-G and IHB-D). Main results were an increase in the proanthocyanidin and soluble carbohydrates content in NIHB−L and IHB−L in relation to LT. There was a reduction of soluble carbohydrate, starch, lipids, nitrogen, and phenolic compounds in infested branches, except in the gall region (IHB-G), which showed an increase of flavonoids and starch contents. It was also observed that NIHB appears to accumulate phenolic compounds. Results showed that P. crassifolium affects the primary and secondary metabolism of T. guianensis, and branches were affected more intense than the leaves. It can be suggested that the parasite withdraws nitrogen and soluble carbohydrates from its host and this could result in possible carbon relocation for growth, development, maintenance, and also defense of branches not yet infested. In addition, it could be suggested the accumulation of phenolic compounds in non−infested branches (NIHB) as a defense mechanism used by the host in order to prevent or even reduce new infestations of an individual already parasitized.

Thesis (M. Ag. Sc.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1997. / Includes bibliographical references (leaves 87-96).