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No description available.

There are relatively few annually resolved climate proxies in arid and semi-arid regions. Columnar cactuses are common in these regions and the stable isotopes of carbon and oxygen in durable spines record variations in rainfall, humidity and ecophysiology as they grow in series along the sides of cactuses. Despite their spines, columnar cactuses provide important ecosystem resources and services in drought prone areas, however, the impact that long-term climate variability and infrequent storms (El Niño or tropical storms) have on the ecology and ecophysiology of columnar cactus is less clear. Stable isotopes in trees and corals serve as useful proxies of climate and ecophysiological information, but for cactus we lack the most rudimentary information about the isotopic systems and their links to the environment. Here, we present an isotopic framework that begins with developing semi-empirical mechanistic models of δ¹³C, δ¹⁸O and δ²H variation in saguaro cactuses that link physical and physiological fractionation factors in stem water and spines to rainfall and humidity. We also review a novel method for determining the age of spines, an important step in developing useful chronologies of isotopic variation in spines. The mechanistic models combined with local climate records enhance our understanding of isotopic variation in daily and annually dated spine δ¹³C and δ¹⁸O records and explain the statistical association of δ¹³C and δ¹⁸O in spines with rainfall, vapor pressure deficit, and El Niño enhanced winter rains. While there are still some challenges to overcome, we expect that isotopic spine series will be used as climate proxies to answer questions regarding regional climate variability or to enhance current models of past and future climates. Likewise, ecophysiologists can use the isotopic spine series in conjunction with gas exchange or carbohydrate studies to look at reproductive or biological responses to changing environments.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Objetivou-se avaliar a influÃncia da adubaÃÃo NPK sobre o crescimento vegetativo, produÃÃo e composiÃÃo quÃmico-bromatolÃgica da palma forrageira (Opuntia ficus-indica Mill.). O experimento foi constituÃdo de dezesseis combinaÃÃes de doses de NPK, conforme matriz experimental Plan Puebla II, distribuÃda em delineamento inteiramente casualizado, com quatro repetiÃÃes. Foram realizadas observaÃÃes dos parÃmetros de crescimento da palma, sendo verificados os aspectos morfomÃtricos: nÃmero de cladÃdios por planta (NC), comprimento (CC), largura (LC), espessura (EC) dos cladÃdios e Ãndice de Ãrea do cladÃdio (IAC). Foram estudadas ainda a produtividade e a composiÃÃo quÃmico-bromatolÃgica da palma forrageira. A produtividade da palma foi influenciada significativamente em face da aplicaÃÃo dos diferentes nÃveis de NPK. Com exceÃÃo da largura as variÃveis morfomÃtricas (comprimento, espessura, nÃmero de cladÃdios por planta e Ãndice de Ãrea de cladÃdio) nÃo foram influenciadas significativamente. A anÃlise de variÃncia para os teores de proteÃna bruta, ao contrÃrio dos valores de matÃria seca evidenciou diferenÃa estatÃstica. Os resultados dos teores de FDA da palma forrageira para os diferentes tratamentos aumentaram ao mesmo tempo em que se elevaram os nÃveis de NPK. As quantidades de nutrientes utilizados nas adubaÃÃes promovem pequenas alteraÃÃes na produÃÃo. A adiÃÃo de NPK promove aumento no teor de proteÃna, o que resulta em melhoria na qualidade nutricional da palma forrageira. / This study aimed to evaluate the influence of NPK fertilization on vegetative growth, yield and chemical composition of cactus pear (Opuntia ficus-indica Mill.). The experiment consisted of sixteen combinations of doses of NPK as Plan Puebla II experimental matrix, distributed in a completely randomized design with four replications. Were performed Observations of the growth of the palm morphometric aspects being checked: number of cladodes per plant (NC) , length (BL) , width (CW) , thickness (CE) and cladodes of the area index of the cladodes (IAC) . Further productivity and chemical composition of cactus pear were studied . The productivity of the palm was influenced significantly based on application of different levels of NPK. Except the width morphometric variables (length, thickness, number of cladodes per plant and leaf area index of cladodes ) were not affected significantly . The analysis of variance for crude protein , unlike the dry matter values statistically different. The results of the FDA rate of cactus pear for the different treatments increased while that increased levels of NPK . The amounts of nutrients used in fertilizers promote small changes in production. The addition of NPK promotes increased protein content, which results in improved nutritional quality of the forage palm.

Biólogo con mención Medio Ambiente / La pérdida de frugívoros a nivel mundial representa una seria amenaza para la persistencia de las plantas, ya que las interacciones dispersor-planta son fundamentales para la reproducción de estas últimas. Sin embargo, en algunos lugares donde los frugívoros nativos han desaparecido, herbívoros introducidos de gran tamaño pueden actuar como dispersores sustitutos. Una vez que las semillas se han dispersado, pueden germinar inmediatamente o formar banco de semillas. Eulychnia acida es una cactácea columnar endémica que habita la región semiárida de Chile. Estudios previos indican que no hay frugívoros nativos asociados a la dispersión de semillas de este cactus dentro de la Reserva Nacional Las Chinchillas. Sin embargo, existen reportes de animales como la cabra (Capra aegagrus hircus) y el guanaco (Lama guanicoe) consumiendo sus frutos a lo largo del rango de distribución de esta cactácea. En este estudio se evaluó el efecto del paso de semillas de E. acida por el tracto digestivo de C. a. hircus y L. guanicoe, sobre la germinación, sobrevivencia y crecimiento de plántulas. Para ello se, alimentó directamente a C. a. hircus y L. guanicoe con frutos de E. acida para obtener semillas desde sus heces , las que posteriormente fueron usadas en experimentos de germinación y crecimiento. Adicionalmente, se evaluó la capacidad de E. acida de formar banco de semillas y si el paso por el tracto digestivo de las semillas afecta en la viabilidad del banco de semillas de E. acida. Para esto se llevaron a cabo experimentos adicionales un año después de que las semillas hubieran sido recuperadas de las heces de los mamíferos. Los resultados indican que el paso de las semillas por el tracto digestivo de C. a. hircus no tiene efecto sobre la germinación, sobrevivencia o crecimiento de E. acida, mientras que L. guanicoe tiene un efecto negativo sobre la germinación. C. a hircus podría actuar como dispersor al llevar las vii semillas lejos de la planta parental, donde la mortalidad debido a causas denso-dependientes es usualmente mayor. Se detectó un aumento en el porcentaje de germinación en ambos tratamientos para el segundo año del experimento, lo que indica que E. acida podría formar al menos a corto plazo un banco de semillas, lo que se traduciría en efectos positivos para poblaciones de esta especie que habitan en un ambiente altamente variable. Son necesarios estudios adicionales que evalúen la dirección y magnitud de las interacciones entre C. a. hircus y la vegetación nativa para poder generar planes de manejo adecuados para la capricultura en el Norte chico de Chile compatibles con la conservación de especies de plantas endémicas de la zona. / Frugivore loss worldwide represents a serious threat for plant persistence because animal disperser-plant interactions are essential for plant reproduction. However, in some places where native frugivorous have disappeared, introduced large herbivore vertebrates may act as surrogate dispersal agents. Once seeds have been dispersed, they can germinate immediately or form a seed bank. Eulychnia acida is an endemic columnar cactus that inhabits the semiarid region of Chile. Previous studies indicate no native frugivorous associated with the dispersal of E. acida inside Las Chinchillas National Reserve. Notwithstanding, there have been reports of goats (Capra aegagrus hircus) and guanacos (Lama guanicoe) consuming its fruit throughout its distribution. In this study the effect of gut passage on the germination, growth and survival of seeds and seedlings of E. acida ingested by L. guanicoe and C. a. hircus was evaluated. To this end, no-choice feeding experiments were performed to obtain seeds consumed by L. guanicoe and C. a. hircus, which were later used in germination and growth experiments. The ability of E. acida to form a seed bank was also examined, and also if gut passage affects the viability of E. acida’s seed bank. To achieve this, additional germination experiments one year after seeds were retrieved from the tested mammals were carried out. Results indicate that C. a. hircus gut passage has no effect on germination, seedling survival or growth, while L. guanicoe had a negative effect on seed germination. C. a. hircus could be carry seeds away from the parent plant where density-dependent seed mortality is usually higher, thus acting as a seed disperser of E. acida. Germination increased the second year of the experiment for both treatments, which indicates that E. acida could form at least a short-term seed bank translating into a positive effect on populations of this species that inhabits a highly ix variable environment. Studies that evaluate the direction and magnitude of biotic interactions between C. a. hircus and the native vegetation are necessary for the generation of adequate programs for the management of C. a. hircus livestock in the North central region of Chile along with conservation of endemic plant species.

Jointed Cactus, Opuntia aurantiaca Lindley (see frontispiece), is the most important weed plant in South Africa, infesting approximately, 1,2 X 10¹° M² and costing approximately R240 000 per annum. Tordon herbicide effectively kills jointed cactus bushes to which it is applied. However, apart from being expensive and damaging to beneficial vegetation, spray programmes have not successfully controlled the weed because most small O. aurantiaca plants are impossible to detect in the field. Biological control may provide a solution to the problem. Two insects, the cochineal bug, Dactylopius austrinus De Lotto and the pyralid moth, Cactoblastis cactorum Berg., already exercise a degree of control over the weed. The introduction into South Africa of other natural enemies such as Zophodia tapiacola (Dyar) from Argentina, South America, may reduce the density of jointed cactus to below an acceptable economic threshold. Any insect considered for release should not colonise and destroy beneficial plants of which the culivated spineless cacti are the most vulnerable. Pre-release studies on Z. tapiacola have shown that it can only colonise a few species of low growing cacti and that it will not damage the large spineless cacti or other desirable plants. Further, the moths are relatively fecund and each larva destroys significant amounts of O. aurantiaca during its development. Consequently, Z. tapiacola is not only considered safe for release but it has the potential to act as a successful biological control agent of O. aurantiaca in South Africa.

Una de las patologías con mayor impacto en la sociedad mundial es la diabetes que está asociada a complicaciones a largo plazo que causan elevada morbi-mortalidad y su origen multifactorial incluye la desregulación del metabolismo de carbohidratos y de lípidos. Se ha demostrado que numerosas hierbas y suplementos dietarios de origen vegetal poseen propiedades hipoglucemiantes e hipolipemiantes y mejoran el estado general del paciente diabético. Las plantas del género Opuntia, principalmente Opuntia ficus-indica, han sido y siguen siendo las más utilizadas, en particular en México. Con respecto a la especie nativa Opuntia megapotamica, hasta el presente no se ha evaluado su toxicidad ni se han llevado a cabo estudios que analicen sus potenciales propiedades medicinales. El objetivo general de este trabajo de Tesis fue evaluar la toxicidad y los efectos de las harinas de cladodios, de pulpa de frutos y de semillas de Opuntia megapotamica sobre la glucemia y los lípidos de ratas normales y diabéticas a través de la realización de estudios in vivo en los cuales se administró, por vía oral, diferentes dosis de las harinas de la planta. Además, se analizó el contenido y la composición de los lípidos de las harinas de cladodios y de semillas. De los ensayos de toxicidad aguda y sub-aguda se determinó que la harina de pulpa no posee efectos tóxicos mientras que las harinas de cladodios y de semillas generan algunas alteraciones histológicas en el hígado y en el riñón que no se traducen en modificaciones en los parámetros bioquímicos ni en cambios en el comportamiento y en el estado general de los animales. La caracterización lipídica de las harinas de cladodios y de semillas, realizada por primera vez en esta especie de Opuntia, indica que la primera por su elevado contenido en ácidos grasos poliinsaturados podría tener un potencial valor nutracéutico. Con respecto a los efectos sobre la glucemia, se estableció que las tres harinas tienen una marcada acción anti-hiperglucemiante en ratas normales con hiperglucemia transitoria mientras que el suministro de las harinas de cladodios y de semillas, durante 30 días, no modifica la glucemia basal en ratas diabéticas. Sin embargo, en estas últimas se observó un leve aumento en los niveles plasmáticos de insulina que podría indicar un incipiente efecto benéfico de la planta sobre el páncreas. En cuanto a los lípidos, se registró un importante efecto hipolipemiante a nivel plasmático, hepático y renal. Solo la harina de cladodios modifica la actividad de las enzimas hepáticas HMG-CoA reductasa y ácido graso sintasa, claves en la biosíntesis de colesterol y de ácidos grasos, respectivamente. La administración de las harinas de cladodios y de semillas produce marcados efectos positivos sobre el funcionamiento del hígado y una leve tendencia al mejoramiento de la función renal. En conjunto, los resultados obtenidos de estos estudios pre-clínicos aportan una información original y muy útil que puede servir como base para futuros estudios clínicos que permitan sustentar el empleo de Opuntia megapotamica como recurso terapéutico. / Diabetes, one of the pathologies with greatest impact on society worldwide, is associated with long-term complications ending in high morbi-mortality. Its multifactorial origin includes carbohydrate and lipid metabolism deregulation. It has been demonstrated that several herbs and dietary vegetal supplements which have hypoglycemic and hypolipidemic properties improve the general conditions of diabetic patients. Plants from Opuntia genus, mainly Opuntia ficus-indica, have been and still are the most used, specially in México. As to the native species Opuntia megapotamica, no studies have been conducted to date to evaluate its toxicity and its potential medicinal properties. The general objective of this Thesis work was to evaluate Opuntia megapotamica toxicity and the effects that cladode, fruit pulp and seed flours exert on glycemia and lipids in normal and diabetic rats. To this end, in vivo studies were carried out in which different doses of cladodes, fruits pulp and seeds were orally administered. The content and composition of lipids from cladode and seed flours were also analyzed. Results from the analyses focused on acute and sub-acute toxicity reveal that whereas fruit pulp flour has no toxic effects, flours from cladodes and seeds produce some histological alterations in liver and kidney which have no correlations with changes in biochemical parameters or in the behavior and general condition of the animals studied. The lipid characterization of cladode and seed flours, carried out for the first time in this Opuntia species, suggests that because of the high polyunsaturated fatty acid content cladode flour could have a potential nutraceutical value. As to Opuntia megapotamica glycemic effects, it was determined that whereas its three flour types have an important anti-hyperglycemic action in normal rats with transient hyperglycemia, cladode and seed flours administration, during 30 days, does not modify basal glycemia in diabetic rats. In the latter, a slight increase in insulin plasmatic levels was registered and it could indicate an incipient plant beneficial effect on the pancreas. Very important hypolipemiant effects in plasma, liver and kidney lipids were also determined. Only cladode flour was observed to modify the activity of the hepatic enzymes HMG-CoA reductase and fatty acid synthase, both of which have key roles in cholesterol and fatty acid synthesis, respectively. The administration of cladode and seed flours produces not only significant positive effects on liver functioning but also a slight tendency to improve renal function. Taken together, the results collected from these pre-clinical studies provide original and useful data that can serve as basis for future clinical research that will enable sustain the use of Opuntia megapotamica as a therapeutic tool.

Thesis (M.S.)--Mississippi State University. Department of Biological Sciences. / Title from title screen. Includes bibliographical references.