Thesis (M.S.)--University of Wisconsin-Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 142-144).

Thesis (Ph. D.)--University of Chicago. / "Reprinted from the Botanical Gazette, vol. 69, no. 1, January, 1920." "Literature cited": p. 52-53.

Bibliography: leaves 100-114. / Human-induced land management practices are key factors which influence the dynamics of landscapes, land elements and biotic communities in Xeric Succulent Thicket, a notoriously fragile and low resilience ecosystem in the Eastern Cape, South Africa. In its natural state this vegetation type is characterized by a continuous mosaic of clumps of diverse woody shrubs in a matrix of grass, hardy dwarf shrubs and bare ground. When indigenous herbivores are replaced by domestic livestock at unsustainable stocking rates, the ratio of clump to interclump areas decreases. This has impacts on biodiversity at the landscape level, and affects the composition and species richness of plant, arthropod and reptile communities and fungal symbionts. The study has two main objectives: 1) to detennine the local-level effects of different types of land use on biodiversity in Xeric Succulent Thicket; and 2) to better understand the factors which affect biodiversity in different taxonomic groups and at different spatial scales, so that the preservation function of protected areas could be enhanced. The key questions which are addressed in the thesis are what does 'biodiversity' mean, and what are its different dimensions in Xeric Succulent Thicket; what roles do protected areas and other lands play in preserving biodiversity, how are different taxonomic groups affected by different types of land use; and how can biodiversity be monitored and measured? . The regional 'conservation landscape' is seen as the protected area plus the land immediately adjoining it, and is viewed as an integrated mosaic of anthropogenic landscapes (land management units), land elements (patches within landscapes). producer communities (assemblages of interacting plant species), consumer communities (assemblages of interacting herbivores and predators) and soil microorganisms. From a process point of view, the research relates the intensity of disturbance, mainly as a result of herbivory, to landscape complexity, the structure of land elements, and the species richness of producers and consumers within land elements. The patterns which emerge are interpreted in the context of ecosystem functioning, from the point of view of a practicing conservation biologist.

Water-use efficiency (WUE) as reflected in the leaf carbon stable isotope ratio was compared between co-occurring indigenous fynbos proteoids and invasive Australian hakeas H. sericea, H. gibbosa and H. suaveolens. At the driest site, H. suaveolens was slightly more WUE than several co-occurring proteoids; there was no significant difference between hakeas and proteas at the other sites. Transpiration rates of shoots and of whole trees were compared between Hakea sericea and Protea repens growing on Stellenboschberg northeast of Cape Town. Both measurements showed no real difference between the species and it is concluded that differences in water relations are not responsible for the highly competitive growth rates of hakeas in fynbos. It is hypothesised that hakeas may be able to vegetatively outcompete proteoids as a consequence of monopodial architecture and some ability to prevent shade-limitation of photosynthesis. A rough estimate of water loss due to transpiration and interception by H. sericea stands indicates that this species may have a significant effect on catchment water loss relative to open-canopy proteoid fynbos. This effect would be due not to transpiration rates of individual trees but to consistently high densities of mature hakea stands.

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The effects of spatial arrangement and density on agronomic efficiency, yield and yield components, dry matter partitioning and growth of an annual cotton/cowpea/maize intercrop were examined in 1990 and 1991 in Tucson, Arizona. The 1990 experiment consisted of four spatial arrangements crossed with four densities of cowpea and maize in a complete factorial design. The 1991 experiment consisted of two densities of cowpea and maize selected from the 1990 experiment in the best spatial arrangement crossed with five densities of cotton in a complete factorial design. A land use efficiency of 12% (or a land equivalent ratio of 1.12) was obtained in the spatial arrangement of single rows of cowpea and maize between singles rows of cotton, whereas a land use efficiency of 11% was obtained for cowpea and maize at a combined density of 50,000 plants/ha intercropped with cotton at a density of 50,000 plants/ha. Maize provided a greater contribution to the land use efficiency than either cotton or cowpea. Cotton yield was highest in the spatial arrangement of single rows of cowpea and maize between single rows of cotton. For the two food crops, cowpea yield was highest in the spatial arrangements in which cowpea and maize were grown in different rows between rows of cotton, whereas maize yield was highest in the spatial arrangements in which cowpea and maize were grown in the same rows between rows of cotton. Cotton fiber quality was not influenced by spatial arrangement, cowpea/maize density, and cotton density. Number of cowpea pods was affected by spatial arrangement in a manner similar to cowpea yield. Number of maize ears increased as cowpea/maize density increased, whereas number of kernels/ear, weight of 100 kernels and length of kernel rows decreased as cowpea/maize density increased. Dry matter accumulation in leaves, stems, and fruits of cotton and cowpea was greatest in the spatial arrangements in which cowpea and maize were grown in different rows between rows of cotton. Weekly cotton growth rate increased as cotton density increased from 39 to 74 days after sowing.

Hedgerows are increasingly being recognised as important in terms of landscape biodiversity. In Britain, recent hedgerows are not valued as highly as ancient hedgerows due to distinct differences in species-richness and historical significance. However, other potential ecological functions of species-poor hedgerows may have been overlooked, especially their potential role as corridors and habitats that help overcome the effects of habitat fragmentation. This thesis examines the spatial and temporal distributions of plant species in recent hedgerows in close proximity to remnant ancient woodland seed sources, and evaluates immigration, colonization and establishment processes that occur at this interface. Transects were used to sample plant species distributions across the transition between remnant ancient woodland communities and adjoining Enclosure Act hedgerows in Northamptonshire. An analysis of the distribution of herbaceous plant species within the seed bank across the woodland- hedgerow transition is also presented. A census of colonizing woody plant species within the Experimental Hawthorn Hedgerows at Monks Wood, in Cambridgeshire was used to investigate the: I) influence of seed source availability, ii) immigration potential, iii) colonization and iv) establishment success under three hedgerow management regimes. Woodland herbaceous plant species were found to have limited spatial and temporal dispersal strategies and species successfully dispersing into adjoining species-poor recent hedgerows were those able to reproduce vegetatively. The seed bank analysis showed that species of disturbed landscapes were dispersing into the woodlands, but were not successfully colonizing. Woody plant species dispersal was found to be operating at a larger spatial scale than herbaceous plant species. The abundance of seed sources and the availability of potential bird dispersers were found to correlate with the colonization success of woody plants within the Experimental Hedgerows, but the survival and establishment was related to hedgerow structure. The implications of these findings in relation to seed source-sink dynamics, corridor theory, habitat function, conservation and landscape planning were considered

Using targeted expression of a constitutively active repressor of GA signalling Susana Ubeda-Tomas et al., (2007) demonstrated that GA action in endodermal cells is necessary for correct root growth. However, GUS studies have shown the final and penultimate GA-biosynthetic genes are not expressed in the endodermis, indicating movement of GAs may be required. This study used the targeted mis-expression of GA degrading enzymes in Col-0 and the attempted targeted rescue of GA biosynthetic and signalling mutants, using the corresponding GA metabolic or signalling component, to gain an insight into the localisation of important GA biosynthesis and signalling sites. This study has demonstrated that GA12 can be made by epidermal, cortical and endodermal cells. However, the ground tissue of the elongation zone does not contain GA12 due to the early GA biosynthetic enzymes only being expressed within cells with a close proximity to the QC. Subsequently the 20-oxidation converts GA12 to GA15, to GA24 to GA9. These reactions mobilise GA allowing it to move from the meristematic region to the elongation zone. GA20ox and GA3ox activity is required in both the meristematic region and the elongation zone for correct root growth to occur. In addition, GA metabolic components are subject to tissue specific GA feedback regulation as a result of post-transcriptional processing and/or post-translational modifications to their protein stability. GA perception in any tissue of the elongation zone can promote complete cell elongation, suggesting that any one tissue can elongate it neighbours, or that each cell is capable of releasing a signal to ensure they all elongate proportionally. The transcriptional network within the endodermis has a disproportionately important role in GAs regulation of cell division within the root proximal meristem but GA action in other cell types is also required. The cambian and bundle sheath cells in aerial tissue like the endodermis in the root contain an important transcriptional network that promotes GA dependant growth.

Early studies of the tomato ethylene signalling network using yeast two-hybrid screen previously identified three novel proteins (IntCR22, 242 and 266) that could interact with a putative ethylene kinase LeCTR2 (Lin et al., 2003). In this study, it has been demonstrated that IntCR22 is a cytoplasmic UDP-glycosyltransferase and IntCR266 is a chloroplast metallo-proteinase homologue to the Arabidopsis FtSH5/VAR1, whereas IntCR242 encodes a novel chloroplast protein with a C-terminal histidine-rich domain. In order to gain more insight into the tomato ethylene signalling mechanism, the sub-cellular localization and protein-protein interactions of the tomato ethylene signalling components have been investigated by fluorescent protein labelling and yeast two-hybrid experiments. Three tomato ethylene receptors (ETR1, NR and ETR4) and a downstream regulator EIN2 have been found in the endoplasmic reticulum (ER). Three putative downstream MAPKK kinases (CTRs) could interact with the C-terminus of the ethylene receptor possibly on the cytoplasmic side of the ER, whereas a novel ethylene signalling component GREEN-RIPE was located in the Golgi. It was therefore concluded from the localization study that IntCR242 and IntCR266 were false positives from the yeast two-hybrid screen and could not interact in vivo with the ethylene signalling components. The results presented in this study, in line with previous ethylene research suggest a possible involvement of the plant endomembrane system in the ethylene signalling network. However, the question as to how the ethylene signal moves from the ER localized receptors to promote activation of genes for the transcription factors within the nucleus remains unsolved.