Thesis (M. Sc.)--University of Western Sydney, Hawkesbury. / "A thesis submitted in fulfilment of the requirements for the degree of Master of Science (Hons), School of Science, Faculty of Science and Technology, University of Western Sydney, Hawkesbury."

Three species of the carnivorous bladderwort Utricularia (U. uliginosa, U. uniflora and U. gibba) were studied in the field to determine the fauna content or prey, within their bladder-traps. The immediate soil/water environment was also sampled to determine the fauna present, in order to enable comparison between the prey fauna and the surrounding fauna. Comparison of the trap fauna with the soil/water fauna revealed evidence of selectivity in trapping: the trap fauna were not simply a random sample of the soil/water fauna. A glasshouse experiment was designed to determine whether the terrestrial bladderwort species U. uliginosa gained any growth advantage from carnivory. Three organism treatments were factorially combined with three Nitrogen levels. The advantage to plants of trapping meiofauna was apparent at the two lower N-levels, but not at the highest N-level. The nitrogen treatments did not confer any significant advantage on plant growth for leaf and trap numbers or stolon length. Nitrogen level did however have a significant effect on leaf area at harvest 2, with plants in the middle nitrogen level having more leaf area than plants in the lower and higher nitrogen levels / Master of Science (Hons)

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Biological Sciences, 2008. / Includes bibliographical references.

Dans cette thèse, nous nous intéressons à la biomécanique de deux mouvements parmi les plus rapides du règne végétal. La première partie porte sur l’étude théorique du mouvement permettant la capture de proies par les pièges de l’utriculaire, des outres déformables de taille millimétrique refermées par une porte flexible. Un modèle dynamique, élaboré à partir d’ingrédients mécaniques, hydrodynamiques et élastiques, permet de relier la différence de pression entre l’intérieur et l’extérieur du piège à la position de la porte via deux équations différentielles couplées. Le modèle permet de capturer la dynamique de fonctionnement du piège et de prédire l’intégralité des comportements observés dans la nature via l’ajout d’un bruit stochastique. La seconde partie est consacrée au mouvement d’éjection des spores par les sporanges de fougères. Notre étude à la fois expérimentale et théorique permet de révéler le caractère remarquable de l’anneau, une structure spécialisée du sporange, dont la nature poroélastique lui confère un comportement comparable à celui d’une catapulte autonome. Les différentes phases du mouvement : ouverture, déclenchement par cavitation, fermeture rapide et recharge éventuelle sont observées via imagerie ultra-rapide. La courbure de l’anneau au cours du mouvement est mesurée expérimentalement puis comparée aux prédictions théoriques pour chacune des phases du mouvement. Cette étude nous permet d’identifier les différents processus physiques à l’origine du mouvement et de déterminer les paramètres caractéristiques de l’anneau : raideur, perméabilité membranaire et pression osmotique interne, ainsi que la pression négative de cavitation. / In this PhD work, we focus on the biomechanics of two motions among the fastest in plant kingdom. The first part is a theoretical study of the motion leading to a prey capture by the bladderwort’s traps, elastic millimeter-sized bladders closed by a flexible door. A dynamical model, based on mechanical, elastic and hydrodynamic ingredients, links the pressure difference between the trap and its surroundings with the door position by the means of two coupled ordinary differential equations. The model captures the dynamics of the trap and predicts all the range of behaviors found in nature by including stochastic noise in the system. The second part focuses on the fern sporangium motion allowing the spores dispersal. Our experimental and theoretical studies point out the remarkable character of the annulus, a specialized structure of the sporangium, as it behaves as an autonomous catapult due to its poroelastic nature. The different stages of the motion: opening, triggering by cavitation, fast closure and eventual reloading are observed using ultra-fast imaging. The annulus curvature is measured experimentally and then compared to the theoretical predictions for each motion phase. This study enables us to identify the physical processes governing the complete motion and to determine the characteristic parameters of the annulus: stiffness, permeability and internal osmotic pressure, and also the negative cavitation pressure.