Leaf recognition for accurate plant classification.

Doctor of Philosophy in Computer Science, University of KwaZulu-Natal, Durban 2017.Plants are the most important living organisms on our planet because they are sources of energy and protect our planet against global warming. Botanists were the first scientist to design techniques for plant species recognition using leaves. Although many techniques for plant recognition using leaf images have been proposed in the literature, the precision and the quality of feature descriptors for shape, texture, and color remain the major challenges. This thesis investigates the precision of geometric shape features extraction and improved the determination of the Minimum Bounding Rectangle (MBR). The comparison of the proposed improved MBR determination method to Chaudhuri's method is performed using Mean Absolute Error (MAE) generated by each method on each edge point of the MBR. On the top left point of the determined MBR, Chaudhuri's method has the MAE value of 26.37 and the proposed method has the MAE value of 8.14. This thesis also investigates the use of the Convexity Measure of Polygons for the characterization of the degree of convexity of a given leaf shape. Promising results are obtained when using the Convexity Measure of Polygons combined with other geometric features to characterize leave images, and a classification rate of 92% was obtained with a Multilayer Perceptron Neural Network classifier. After observing the limitations of the Convexity Measure of Polygons, a new shape feature called Convexity Moments of Polygons is presented in this thesis. This new feature has the invariant properties of the Convexity Measure of Polygons, but is more precise because it uses more than one value to characterize the degree of convexity of a given shape. Promising results are obtained when using the Convexity Moments of Polygons combined with other geometric features to characterize the leaf images and a classification rate of 95% was obtained with the Multilayer Perceptron Neural Network classifier. Leaf boundaries carry valuable information that can be used to distinguish between plant species. In this thesis, a new boundary-based shape characterization method called Sinuosity Coefficients is proposed. This method has been used in many fields of science like Geography to describe rivers meandering. The Sinuosity Coefficients is scale and translation invariant. Promising results are obtained when using Sinuosity Coefficients combined with other geometric features to characterize the leaf images, a classification rate of 80% was obtained with the Multilayer Perceptron Neural Network classifier. Finally, this thesis implements a model for plant classification using leaf images, where an input leaf image is described using the Convexity Moments, the Sinuosity Coefficients and the geometric features to generate a feature vector for the recognition of plant species using a Radial Basis Neural Network. With the model designed and implemented the overall classification rate of 97% was obtained

High Resolution Maps of the Vasculature of An Entire Organ

The structure of vascular networks represents a great, unsolved problem in anatomy. Network geometry and topology differ dramatically from left to right and person to person as evidenced by the superficial venation of the hands and the vasculature of the retinae. Mathematically, we may state that there is no conserved topology in vascular networks. Efficiency demands that these networks be regular on a statistical level and perhaps optimal. We have taken the first steps towards elucidating the principles underlying vascular organization, creating the rst map of the hierarchical vasculature (above the capillaries) of an entire organ. Using serial blockface microscopy and fluorescence imaging, we are able to identify vasculature at 5 μm resolution. We have designed image analysis software to segment, align, and skeletonize the resulting data, yielding a map of the individual vessels. We transformed these data into a mathematical graph, allowing computationally efficient storage and the calculation of geometric and topological statistics for the network. Our data revealed a complexity of structure unexpected by theory. We observe loops at all scales that complicate the assignment of hierarchy within the network and the existence of set length scales, implying a distinctly non-fractal structure of components within

A taxonomic revision of the tribe Desmodieae (Leguminosae - Papilionoideae)

Thesis (M.Sc.)-University of Durban-Westville, 1984.The tribe Desmodieae has a pantropical distribution and is one of the most advanced tribes in the subfamily Papilionoideae. Despite this fact, the tribe was already present in the fossil record of the early Tertiary and so the Papilionoideae appear to be much older than is currently accepted. With its greatest centres of development in tropical Asia and America, Africa is relatively poorly endowed and only four genera comprising sixteen species occur in the Flora of southern Africa. Many of these species are widespread in the old World tropics and the few African endemics appear to be closely related to them. Desmodium is the largest genus with the bulk of species belonging to the Asian subgenus Sagotia. Of the two sections of Sagotia represented in Africa, section Nicolsonia is clearly more derived than section Heteroloma, showing many characters intermediate between Heteroloma and the considerably more derived genera Alysicarpus and Lespedeza. Other Desmodium species either of the Old or New World have often become naturalised as weeds in Africa. Pseudarthria is a genus derived by an aneuploid increase of the basic x = 11 for the tribe rather than an aneuploid decrease as in the case of Alysicarpus and Lespedeza. A re-count of the chromosome number of P. hookeri (2n = 26) matches the count obtained in another species of Pseudarthria for the first time. Flowering strategy and flower structure in the tribe are the result of intense coevolution with the ecological requirements of skilled bee pollinators and although many bees can trip Desmodieae flowers, only a relatively few high energy demanding, traplining bees are able to bring about effective pollination. The overall breeding system represents a fine balance between the need for selfing and the need for outcrossing in order to produce enough seed of sufficient quality to survive in unstable environments

Biosystematic studies in Southern African species of Strychnos L. (Loganiaceae)

Ph. D. University of KwaZulu-Natal, Durban 2014.Strychnos L. is the largest genus of the pantropical or subtropical family Loganiaceae with about 200 species. Their habits range from trees and shrubs in open areas to lianas in rain forests. The genus is well-known as a source of alkaloids such as strychnine and brucine and other allied compounds, all of which have been used medicinally and in curare formulation for centuries. While taxonomic circumscription of the genus has never been contentious, there is no consensus about infrageneric affiliations, the latest of which recognises 12 sections based on morphological characters. Recent molecular evaluation of the genus on a global scale with the internal transcribed spacer (ITS) marker suggests that many of the currently recognised sections are not monophyletic. An understanding of regional patterns of evolution, which is relevant for biodiversity conservation, requires an in-depth study of the focus group on a regional scale. Using a multiplicity of approaches from morphological and molecular to biogeographical, this study is an attempt at elucidating diversity patterns at different levels among the southern African species of Strychnos. Various combinations of morphological attributes from branches, leaves, flowers and fruits distinguish seemingly homologous clusters of species, sometimes supported by molecular data. A lack of molecular support for a hypothetical relationship may viii indicate case(s) of convergent evolution in these features across the taxa involved. Molecular phylogenies based on the ITS and chloroplast markers confirm the nonmonophyletic nature of all but section Spinosae. Proposals for sectional recircumscriptions of the genus are provided. Patterns of speciation within Strychnos suggest a Miocene origin in the rain forests along the South America/Guinea-Congolian axis. Within the southern African subcontinent, the evolution of the genus carries a strong ecological signature along either the forest or savanna biome, with many accompanying morphological adaptations for the respective habitats. The non-synonymy of S. gerrardii with S. madagascariensis is demonstrated with multiple sources of data, as a case of integrative taxonomy succeeding where single-source data approaches might have failed. Routes to current distribution of the genus in southern Africa are hypothesised to involve a combination of palaeo-climatic oscillations and allopatric speciation, consistent with the process indicated in many other plant groups for the region. The findings are discussed in the wider context of their implications for taxonomy and biodiversity conservation in the face of climate change, food security and other relevant issues in systematics

Journal of Hymenoptera research.

v.16:no.2 (2007

Dynamic networks. An interdisciplinary study of network organization in biological and human social systems

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Insects

In this thematic series, engineers and scientists come together to address two interesting interdisciplinary questions in functional morphology and biomechanics: How do the structure and material determine the function of insect body parts? How can insects inspire engineering innovations