Morphological and anatomical effects of pyrazon, 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone, on Phaseolus vulgaris L. and Amaranthus retroflexus L. were studied after treatment of seeds or seedlings at various pyrazon concentration, exposure times and environmental regimes. Beans treated with pyrazon developed various chlorotic and necrotic symptoms on the unifoliate leaves. Chlorosis and necrosis were observed first on the leaf margins. Beans treated with pyrazon under a complete dark regime developed symptoms much later than those under an alternating light and dark regime. Pyrazon treated pigweed displayed symptoms similar to those on beans. Pyrazon induced abnormal chloroplasts and graded cellular collapse in the unifoliate leaves of beans and cotyledons of pigweed. The severity and/or extent to which morphological and anatomical symptoms developed were dependent upon herbicide concentration, exposure and treatment regime.

A character data set suitable for cladistic analysis of tardigrades at the family level was developed. The data matrix consisted of 50 morphological characters from 15 families of tardigrades and was analyzed by maximum parsimony. Kinorhynchs, loriciferans and gastrotrichs were used as outgroups. The results agree with the currently accepted hypothesis that Eutardigrada and Heterotardigrada are distinct monophyletic groups. Among the eutardigrades, Eoyhypsibiidae was found to be a sister group to Macrobiotidae + Hypsibiidae, while Milnesiidae was the basal eutardigrade family. The basal heterotardigrade family was found to be Oreellidae. Echiniscoideans grouped with some traditional Arthrotardigrada (Renaudarctidae, Coronarctidae + Batillipedidae) suggesting that the arthrotardigrades are not monophyletic. An 18S rRNA phylogenetic hypothesis was developed and supports the monophyly of Heterotardigrada and of Parachela versus Apochela within the Eutardigrada. Mapping of habitat preference suggest that terrestrial tardigrades are the ancestral state. Molecular analysis of a sediment sample with an unusually large population of tardigrades had a higher diversity when compared to manual sorting and counting.

In this Ph.D. work, we investigate the optoelectronic properties of low-bandgap semiconducting polymers and project the potential for employing these materials in electronic and photonics devices, with a particular emphasis on use in organic solar cells. The field of organic solar cells is well developed and many of the fundamental aspects of device operation and material requirements have been established. However, there is still more work to be done in order for these devices to ultimately reach their full potential and achieve commercialization. Of immediate concern is the low power conversion efficiency demonstrated in these devices so far. In order to improve upon this efficiency, several routes are being explored. Because the optical bandgaps of semiconducting polymers are larger than in inorganic semiconductors, one of the most promising routes currently under exploration is the development of low-bandgap materials. Using polymers with lower band gaps will allow more of the solar irradiance spectrum to be absorbed and converted into electricity and thus possibly boost the overall efficiency. The bandgap of these semiconducting polymers is determined by the chemical structure, and therefore can be tailored through synthesis if the relevant structure-property relationships are well-understood. The materials studied in this work, a new series of Poly(thienylenevinylene) (PTV) derivatives, posses lower band gaps than conventional polymers through a design that incorporates aromatic-quinoid structural disturbances. This type of chemical structure delocalizes the electronic structure along the polymer backbone and reduces the energy of the lowest excited-state leading to a smaller band-gap. We investigate these materials through a variety of techniques including linear spectroscopy such as absorption and photoluminescence, pump-probe techniques like cw-photoinduced absorption and transient photo-induced absorption, and the non-linear electroasborption technique in order to interrogate the consequences of the delocalized electronic structure and its response to optical stimuli. We additionally consider the effects of environmental factors such as temperature, solvents and chemical doping agents. During the course of these investigations, we consider both of the two primary categorical descriptions of structure-property relationships for polymers within the molecular exciton model, namely the role of inter-molecular interactions on the electronic properties through the variation of supermolecular order and the fundamental determination of electronic structure due to specific intra-molecular interaction along the backbone of the polymer chain. We show that the dilution of aromaticity in semiconducting polymers, while being a viable means of reducing the optical band gap, results in a significant increase in the role of electron-electron interactions in determining the electronic properties. This is observed to be detrimental for device performance as the highly polarizable excited state common to polymers gives way to highly correlated state that extinguishes both the emissive properties and more importantly for solar cells, the charge-generating characteristics. This situation is shown to be predominant regardless of the nature of interchain interactions. We therefore show that the method of obtaining low-bandgap polymers here comes along with costly side-effects that inhibit their efficient application in solar cells. Further, we directly probe the efficacy of these materials in the common bulk-heterojunction architecture with both spectroscopy and device characterization in order to determine the limiting and beneficial factors. We show that, while from the point of view of absorption of solar radiation these low-bandgap polymers are more suited for solar cells, the ability to convert the absorbed photons into electron-hole pairs and generate electricity is lacking, due to the internal conversion into the highly correlated state and thus, the absorbed photon energy is lost. For completeness, we fabricate devices and verify that both the charge-transport properties and alignment of charge extraction levels with those of the contacts can not be responsible for the dramatic decrease in efficiency found from these devices as compared to other higher band gap polymers. We thus conclusively determine that the lack of power converison efficiency is governed by the inefficiency of charge-generation resulting from the intrinsic defective molecular structures rendering a low-lying optically forbidden state below the lowest optical allowed state that consumes the majority of the photogenerated excitons. It is emphasized that our means of investigation allow us to truly access the potential of these materials. In contrast, the direct application of these systems in devices and interpretation of the performance is exceedingly complex and may obscure their true potential. In other words, poor performance from a device may be extrinsic in nature and the optimization process may be very costly with respect to both time and materials. The methods used here however, allow us to determine the intrinsic potential. Not only is this beneficial in terms of preserving the resources that would be used on the trial-and-error method for devices, but it also allows us to learn more on a fundamental level about the structure-property relationships and their implications for device performance. The benefits of this increased understanding are two-fold. First, by learning about the fundamental response of a material, a new application may be realized. For example, the rapidly efficient internal conversion process that renders the materials in this study as poor candidates for solar cells may make them useful for photonics applications, as optical switches, for instance. Secondly, this type of investigation has implications for the whole organic electronics community instead of just being limited to the particular material system and the primary application attempted. In this case, we are essentially able to determine a threshold for aromaticty necessary in a structure that will preserve the stability of the ionic excited state that is useful for charge generation in solar cells.

No description available.

No description available.

No description available.

No description available.

Temnospondyls are large extinct fossil tetrapods; superficially resembling crocodiles in their general size, appearance and lifestyle. Temnospondyls are a group of early tetrapods, the oldest fossils are more than 340 million years old, and they existed for more than 200 million years. This doctoral thesis examined the postcranial skeleton of temnospondyls and its evolutionary history and diversification. Standard taxonomic techniques were used to distinguish between the types of variation observed in the postcranial skeleton and for phylogenetic analysis. The thesis consists of a series of published articles, three describing the postcranial skeletons of various temnospondyls, and three summary articles, all with extensive illustrations. To provide data, the postcranial skeletons of three temnospondyl taxa were described. The articulated postcranial skeleton of a basal stereospondyl (rhinesuchid) is immature, and paedomorphism of the postcranial skeleton in stereospondyls is discussed. The robust appendicular skeleton of Eryops megacephalus is plesiomorphic, well-ossified, and terrestrially adapted. The paedomorphic postcranial skeleton of Trimerorhachis insignis is plesiomorphic, and secondarily aquatic, the description includes growth stages. This study found that extensive morphogenetic variation is present in the postcranial skeleton of temnospondyls. Many phylogenetically significant characteristics develop with morphogenesis, they may be absent in early growth stages, and may never develop even in the largest growth stages of taxa with paedomorphic postcranial skeletons. Consequently, assessment of the presence or absence of a phylogenetically significant characteristic in any taxon may be dependant on the morphogenetic stage of the specimen examined. This finding has major implications for the phylogenetic analysis of temnospondyls and other early tetrapods. An overview of phylogenetic variation in the postcranial skeleton is presented, including a large phylogenetic analysis of the Temnospondyli. The most primitive temnospondyls possess fully ossified postcranial skeletons, well adapted for terrestrial locomotion, but some of the derived clades of temnospondyls have paedomorphic postcranial skeletons and are exclusively aquatic. For the first time, the postcranial skeleton of temnospondyls is comprehensively compared with that of other early tetrapods in the largest phylogenetic analysis to date, resulting in the unexpected discovery that temnospondyls are most closely related to the ancestors of amniotes. The Temnospondyli plus Neospondyli (Seymouriamorpha plus Cotylosauria plus Lepospondyli) forms a large new clade, the Terrapoda, defined by the presence of many derived synapomorphies. Some of the cranial synapomorphies of the Terrapoda are most likely related to improvements in hearing. The postcranial synapomorphies indicate that the Terrapoda are the first vertebrates to have evolved limbs that are well adapted for terrestrial locomotion. The Terrapoda are the first truly terrestrial vertebrates, their postcranial adaptations facilitated their colonisation of the land and consequent phylogenetic radiation during the early Carboniferous. Both analyses incorporate characters from previous analyses and many new postcranial characters. The results of the phylogenetic analyses are statistically more parsimonious than previous analyses and have much lower levels of homoplasy. Comparative analyses indicate that the distinctive results are most likely due to the increased use of characters pertaining to temnospondyls, increased use of postcranial characters, and differentiation between sources of morphological variation to minimise morphogenetic and phenotypic variation and elucidate true phylogenetic signal.

Three perennial tropical Panicum species were grown under ambient and elevated (900 ppm) carbon dioxide concentrations in especially designed microclimate chambers. The study aimed to investigate the influence of high carbon dioxide concentrations on morphology/anatomy with physiological change among three closely related species possessing distinctly different photosynthetic pathways. The anatomy of the leaf was investigated using light microscopy (LM), transmission electron microscopy (TEM), and graphics image analysis. A suitable schedule for fixation, dehydration and embedding of leaf specimens for both forms of microscopy was developed. The anatomy of the species investigated did not change qualitatively, but there were detectable changes in leaf thickness and tissue proportions of the epidermis, mesophyll and thickened tissues (sclerenchyma, bundle sheath, vascular elements) that differed with species. This study is also relevant to the investigation of the evolution of C4, although species, and the progression involved in plants with characteristics intermediate between those of C3 and C4 species. These intermediate species have been mainly characterized by CO2 exchange and biochemical analysis, but they also display anatomical characteristics in between those of C3 and C4 plants. The evolutionary progression of the C3 to C4 species remains unsolved, although current studies indicate that the evolutionary step was from the C3 plant to the C4. Thus the intermediate C3/C4 plants may not be intermediate in an evolutionary sense and they could be seen as a simple hybridization between a C3 plant and C4 plant. In most of the parameters measured the C3/C4 P. decipiens resembled either the C3 P. tricanthum or the C4 P. antidotale. It may therefore be likened to a physiological chimera rather than to a true intermediate form / Doctor of Philosophy (PhD)

Coexisting species are interesting from evolutionary and ecological perspectives. Sympatry can provide insights into mechanisms that allow stable long-term coexistence, such as niche partitioning, character displacement, interspecific competition and species boundaries. In New Zealand streams, a flock of closely related non-migratory galaxiid fishes exist throughout eastern South Island (Galaxias vulgaris sensu lato). These fishes are largely parapatric, but recent studies have found streams that contain coexisting populations of two newly discovered galaxiids (Galaxias �southern� and G. gollumoides). In such streams there is a cline from allotopic (sections of streams containing predominantly one species) G. �southern� (lower altitudes) to allotopic G. gollumoides (higher altitudes), with a syntopic (both species) transition section. Such coexistence makes G. �southern� (yet to be formally described) and G. gollumoides ideal for examining the ecology and evolution of sympatric taxa. Very little is known about these two taxa. This thesis aims to detail the morphology, ecology and genetic differentiation between G. �southern� and G. gollumoides. These factors will be used to address separate species status and the possibility of interspecific competition. Data will also be used to examine resource and morphological shifts in either species between syntopy and allotopy, which maybe consistent with character displacement theory. All fish collected for analysis were first classified as G. �southern� or G. gollumoides by eye and by mtDNA. Morphological and ecological (habitat use and diet/isotope enrichment) differentiation between the two species were examined from three sympatric streams (streams containing allotopic and syntopic sites; representing three separate catchments) and four allopatric streams (streams containing only allotopic sites; representing two separate catchments). For sampling purposes, sympatric streams were subdivided into lower (allotopic G. �southern�), mid (syntopic) and upper (allotopic G. gollumoides) sections. We used this sampling regime to test for character displacement (i.e. ecological and morphological shifts between syntopy and allotopy). Diet, stable isotope, genetic structuring and hybridisation (amplified fragment length polymorphisms) were analysed from the three sympatric streams. Artificial stream channels were also used to observe the influence of interspecific competition on resource use over a complete diel cycle. G. �southern� and G. gollumoides were found to be morphologically distinct, differing significantly in 21 of 25 morphological measurements. The two species were also segregated ecologically with G. �southern� preferring shallower water, coarser substrate, and higher water velocity, feeding predominantly on mayflies (Ephemeroptera). In contrast, G. gollumoides preferred deeper water, finer substrate and lower water velocity, feeding predominantly on terrestrial invertebrates. Dietary segregation was also reflected by differences in [delta]�� Carbon and [delta]�⁵ Nitrogen enrichment. Morphological shifts consistent with character displacement were seen in overbite size and mouth size, but neither trait showed consistent statistical differences within and across streams. Ecological shifts were seen in distance to the nearest cover, with G. gollumoides being found further away from cover in syntopy and G. �southern� being found the same distance away from cover in syntopy and allotopy. In artificial stream channels, resource use of both species was not affected by the presence of a congener, but both species used faster water velocities during the night while remaining ecologically distinct. AFLP analysis revealed distinct genotypic clustering between these species with no F1 hybrids. Fine-scale genetic structuring was also observed within both species among streams, and among sites within streams. The minimal effect of a congener on resource use suggests that interspecific competition is not a strong force shaping sympatric populations of Southland galaxiids. This is also reflected by the lack of consistent morphological shifts between allopatry and sympatry. Similarly, character displacement does not seem to be a strong influencing G. �southern� and G. gollumoides. Diel cycles influenced niche expression in both fishes suggesting that abiotic factors may be important in structuring freshwater fish communities in Southland. The fine-scale genetic structuring within both species suggests limited conspecific genetic mixing and movement within streams, which possibly reflects drainage evolution. The absence of F1 hybrids suggests reproductive isolation between G. �southern� and G. gollumoides which may be associated with assortative mating. The present study provides evidence for the separate status of these sympatric fishes under several species concepts. There is conclusive evidence for morphological, ecological and genetic differentiation between sympatric G. �southern� and G. gollumoides, and such segregation maybe associated with long term coexistence in nature. Key words: coexistence, ecology, morphology, genetics, G. �southern�, G. gollumoides.