2 pp. / Until the introduction of semi-dwarf wheat in the late 1960s, wheat varieties were typically one and a half to two times their current height. Most heirloom, traditional, or landrace varieties are considered standard-height wheat (e.g. Sonoran white); in general they are adapted to lower-input conditions, and cannot tolerate high-fertility environments without lodging. Lodging reduces grain yield, delays harvest, and increases harvesting costs. Standard-height wheat needs to be grown at a lower plant density and with less nitrogen and irrigation water than semi-dwarfs in order to prevent lodging, optimize yield, and make the most efficient use of resources.

Monitoring ecological restoration at the community scale provides insight into how the population dynamics and community interactions are progressing through time in comparison to a restoration’s goals and reference conditions. This study monitored the early post-restoration dynamics of a sand plain located in the Carolinian Canada ecozone called Lake Erie Farms. The restoration consisted of restoring three habitats via sculptured seeding: a mesic forest, oak woodland, and sand barren. The hypothesis of this study is that the restoration efforts have established population dynamics and community interactions consistent with successional patterns expected from comparative literature. Community ecology, directed succession, and alternative stable states are the underlying theories that provided a conceptual and theoretical lens from which to study the objectives and hypothesis. To gain insight into the community dynamics at Lake Erie Farms the vegetation abundance, seed abundance and viability of the seedbank, seed viability of the 6 most dominant species (3 most dominant native species & 3 most dominant weedy species), and soil moisture & pH were monitored. The analysis was conducted using a RMANOVA of a nested design (P > 0.001, 0.01 and 0.05) to compare the variables in relation to the site (i.e. the sum of all the quadrats), the restoration treatment nested within the site, the field nested within the site, the transect nested within the restoration treatment and the quadrat nested within the restoration treatment. The significant findings of this study include: i) the restoration treatments are producing similar results as those expected from the literature, though there is evidence of the sculptured seeding treatment accelerating the successional stage at Lake Erie Farms compared to abandoned agricultural fields in similar ecosystems because of the presence of later-successional species; ii) the control areas are less diverse than each of the restoration units (P>0.05); and iii) the soil moisture among the treatments is beginning to diverge into the desired restoration units.

Restoration and rehabilitation activities are presently considered to be a major priority in environmental management, whether the activity implies the restoration of neglected cultivated pastures or degraded rangelands due to overgrazing and climatic impacts, or the rehabilitation of the mining and industrial areas. However, the goals are not easily achieved, mainly due to the high input costs, including that of re-seeding activities. Reseeding success is influenced by the quality and effectiveness of the used seed regarding germination and establishment under natural field conditions. If techniques can be developed to enhance the effectiveness of germination and establishment percentage of the seed in restoration and rehabilitation sites, a better cover, density and biomass yield can be expected, which will improve the rehabilitation process. It is known that commercially available grass seed has a better germination percentage and establishment percentage in comparison with seed locally harvested, which may include many impurities such as sticks and stones. The availability of the locally harvested seed types, especially of certain ecotypes adapted to specific environments, can be poor. Advance Seed Company (Krugersdorp, South Africa) has taken commercially available grass seed to the next level by enhancing (coating) the seed with a multitude of different treatments to ensure better handling of the seed in reseeding applications. These treatments also have advantages such as a higher seed to soil contact, growth stimulants included in the treatment, higher seed purity and the protection of the seed against predation by ants and other insects and against harsh chemicals in the soil, which might have an influence on the germination percentage of the seed and the establishment of seedlings. The objective of this study was to investigate whether or not certain enhanced grass seed types of selected grass species will have a better germination and establishment percentage, fresh and dry above-(leaves) and below-ground (root) biomass yield (glasshouse trials) and dry above-ground biomass yields (natural fields trials) in comparison with non-enhanced types. The predation of enhanced and non-enhanced seeds by ants and other insects, as well as the development of the vascular tissue in the transitional region of the seedlings was also investigated. The grasses assessed included enhanced and non-enhanced seed types of Chloris gayana (Rhodes grass), Cynodon dactylon (Couch grass), Digitaria eriantha (Common finger grass) and Eragrostis curvula (Weeping love grass). In the case of E. curvula, four seed types, including the non-enhanced seed type were tested. These included non-enhanced seed, seed treated with "plain coat", enhancement with "organic insecticide on the base of the coaf' (Le. insecticide between the enhancement and the seed) and enhancement with "organic insecticide on the base of the coat and as an overspray" (Le. insecticide between the enhancement and the seed, as well as spraying the insecticide over the coated seed). The above mentioned species are commonly used in grass seed mixtures for rehabilitation and restoration purposes. Seeds were supplied by Advance Seed Company. The seed enhancement treatments as well as the non-enhanced seed types were tested under various conditions. The chemical composition of the enhancement treatment used in the coating process is only known by the seed technicians at Advance Seed Company. All the seed supplied by the seed merchant had a purity of >95%. With the application of dormancy breaking in the germination tests the non-enhanced seed types of Chloris gayana had the higher germination percentage of the seed type or the same species. Other differences included the germination percentage being significantly higher for the enhanced seed type of Cynodon dactylon than the non-enhanced seed type. Lower germination percentages were noted in the comparison of the E. curvula seed types, were the non-enhanced seed type had a higher germination percentage in comparison with the enhanced seed types. In the germination tests without dormancy breaking being applied, these results differ. With regard to the establishment percentages, similar statistical differences were noted in both the Coco Peat Moss medium and the Hygromix growth medium. In the above-and below-ground biomass production trials in the glass house the only significant difference were noted in the biomass production of D. eriantha plants. In the case of the dry above-and below-ground biomass yield the plants of the non-enhanced seed types of D. eriantha yielded a significantly higher biomass in comparison with the plants harvested from the enhanced seed type of the same species. With regard to the natural field trials a few significant differences were noted. The results indicated that the enhanced seed types of Chloris gayana and Cynodon dactylon, the non-enhanced seed type of D. eriantha as well as the non-enhanced and "organic insecticide on base and as overspray" enhancement of E cUNula can be used in re-seeding restoration and rehabilitation practices. Eragrostis cUNula enhanced with "plain coat" is not recommended to be used for re-seeding in disturbed areas. / Thesis (M.Sc. (Environmental Science and Management))--North-West University, Potchefstroom Campus, 2008.

Restoration and rehabilitation activities are presently considered to be a major priority in environmental management, whether the activity implies the restoration of neglected cultivated pastures or degraded rangelands due to overgrazing and climatic impacts, or the rehabilitation of the mining and industrial areas. However, the goals are not easily achieved, mainly due to the high input costs, including that of re-seeding activities. Reseeding success is influenced by the quality and effectiveness of the used seed regarding germination and establishment under natural field conditions. If techniques can be developed to enhance the effectiveness of germination and establishment percentage of the seed in restoration and rehabilitation sites, a better cover, density and biomass yield can be expected, which will improve the rehabilitation process. It is known that commercially available grass seed has a better germination percentage and establishment percentage in comparison with seed locally harvested, which may include many impurities such as sticks and stones. The availability of the locally harvested seed types, especially of certain ecotypes adapted to specific environments, can be poor. Advance Seed Company (Krugersdorp, South Africa) has taken commercially available grass seed to the next level by enhancing (coating) the seed with a multitude of different treatments to ensure better handling of the seed in reseeding applications. These treatments also have advantages such as a higher seed to soil contact, growth stimulants included in the treatment, higher seed purity and the protection of the seed against predation by ants and other insects and against harsh chemicals in the soil, which might have an influence on the germination percentage of the seed and the establishment of seedlings. The objective of this study was to investigate whether or not certain enhanced grass seed types of selected grass species will have a better germination and establishment percentage, fresh and dry above-(leaves) and below-ground (root) biomass yield (glasshouse trials) and dry above-ground biomass yields (natural fields trials) in comparison with non-enhanced types. The predation of enhanced and non-enhanced seeds by ants and other insects, as well as the development of the vascular tissue in the transitional region of the seedlings was also investigated. The grasses assessed included enhanced and non-enhanced seed types of Chloris gayana (Rhodes grass), Cynodon dactylon (Couch grass), Digitaria eriantha (Common finger grass) and Eragrostis curvula (Weeping love grass). In the case of E. curvula, four seed types, including the non-enhanced seed type were tested. These included non-enhanced seed, seed treated with "plain coat", enhancement with "organic insecticide on the base of the coaf' (Le. insecticide between the enhancement and the seed) and enhancement with "organic insecticide on the base of the coat and as an overspray" (Le. insecticide between the enhancement and the seed, as well as spraying the insecticide over the coated seed). The above mentioned species are commonly used in grass seed mixtures for rehabilitation and restoration purposes. Seeds were supplied by Advance Seed Company. The seed enhancement treatments as well as the non-enhanced seed types were tested under various conditions. The chemical composition of the enhancement treatment used in the coating process is only known by the seed technicians at Advance Seed Company. All the seed supplied by the seed merchant had a purity of >95%. With the application of dormancy breaking in the germination tests the non-enhanced seed types of Chloris gayana had the higher germination percentage of the seed type or the same species. Other differences included the germination percentage being significantly higher for the enhanced seed type of Cynodon dactylon than the non-enhanced seed type. Lower germination percentages were noted in the comparison of the E. curvula seed types, were the non-enhanced seed type had a higher germination percentage in comparison with the enhanced seed types. In the germination tests without dormancy breaking being applied, these results differ. With regard to the establishment percentages, similar statistical differences were noted in both the Coco Peat Moss medium and the Hygromix growth medium. In the above-and below-ground biomass production trials in the glass house the only significant difference were noted in the biomass production of D. eriantha plants. In the case of the dry above-and below-ground biomass yield the plants of the non-enhanced seed types of D. eriantha yielded a significantly higher biomass in comparison with the plants harvested from the enhanced seed type of the same species. With regard to the natural field trials a few significant differences were noted. The results indicated that the enhanced seed types of Chloris gayana and Cynodon dactylon, the non-enhanced seed type of D. eriantha as well as the non-enhanced and "organic insecticide on base and as overspray" enhancement of E cUNula can be used in re-seeding restoration and rehabilitation practices. Eragrostis cUNula enhanced with "plain coat" is not recommended to be used for re-seeding in disturbed areas. / Thesis (M.Sc. (Environmental Science and Management))--North-West University, Potchefstroom Campus, 2008.

Articular cartilage disorders are a leading cause of human disability in many countries around the world. In this work, new techniques and strategies were developed to improve the quality of cartilage produced in vitro by methods of tissue engineering. Chondrocytes were isolated from the hip and knee joints of aborted human foetuses. The cells were expanded and seeded into scaffolds and the seeded scaffolds were cultured in perfusion bioreactors. The quality of the final cartilage constructs was assessed biochemically by measuring their content of glycosaminoglycan (GAG), total collagen and collagen type II and histologically by staining cross-sections of the constructs for GAG, collagen type I and collagen type II. The amount of proteoglycan released in the culture medium was also measured at regular intervals. Proteoglycans from tissue-engineered cartilage and spent culture medium were compared and analysed for degradation and capability of aggregation. During monolayer expansion, the chondrocyte differentiation indices decreased, the cell size increased and the percentage of cells present in G2/S??M phase decreased with the greatest changes occurring during the first passage. Expanding chondrocytes in PGA or PGA??alginate scaffolds produced cells with a higher level of differentiation than monolayer-expanded cells. However, PGA and PGA??alginate could not be justified as suitable systems for the routine expansion of chondrocytes mainly because of the relatively low cell proliferation obtained. Two new methods for seeding of cells into scaffolds were investigated using PGA and PGA??alginate as scaffold materials. Both methods produced high seeding efficiencies and homogeneous distribution of cells. When seeded PGA??alginate scaffolds were cultured in perfusion bioreactors, they produced good quality constructs with higher concentrations of extracellular matrix (ECM) components compared with previously described methods. However, when seeded PGA scaffolds were cultured in perfusion bioreactors, they produced small constructs of poor quality. Investigation of the effect of medium flow rate on the PGA scaffolds showed that a low flow rate was needed at the beginning of the culture to enable the cells to form a framework onto which other synthesised elements could deposit. Applying a gradual increase in medium flow rate to PGA scaffolds cultured in perfusion bioreactors solved the shrinkage problem and produced constructs with quality similar to those produced using PGA??alginate scaffolds. A novel compression bioreactor that mimicked the physiological stimulation of cartilage by joint movement was constructed. Using this bioreactor, compressed constructs showed significantly higher wet weight and higher concentrations of GAG, total collagen and collagen type II compared with non-compressed constructs.

Articular cartilage disorders are a leading cause of human disability in many countries around the world. In this work, new techniques and strategies were developed to improve the quality of cartilage produced in vitro by methods of tissue engineering. Chondrocytes were isolated from the hip and knee joints of aborted human foetuses. The cells were expanded and seeded into scaffolds and the seeded scaffolds were cultured in perfusion bioreactors. The quality of the final cartilage constructs was assessed biochemically by measuring their content of glycosaminoglycan (GAG), total collagen and collagen type II and histologically by staining cross-sections of the constructs for GAG, collagen type I and collagen type II. The amount of proteoglycan released in the culture medium was also measured at regular intervals. Proteoglycans from tissue-engineered cartilage and spent culture medium were compared and analysed for degradation and capability of aggregation. During monolayer expansion, the chondrocyte differentiation indices decreased, the cell size increased and the percentage of cells present in G2/S??M phase decreased with the greatest changes occurring during the first passage. Expanding chondrocytes in PGA or PGA??alginate scaffolds produced cells with a higher level of differentiation than monolayer-expanded cells. However, PGA and PGA??alginate could not be justified as suitable systems for the routine expansion of chondrocytes mainly because of the relatively low cell proliferation obtained. Two new methods for seeding of cells into scaffolds were investigated using PGA and PGA??alginate as scaffold materials. Both methods produced high seeding efficiencies and homogeneous distribution of cells. When seeded PGA??alginate scaffolds were cultured in perfusion bioreactors, they produced good quality constructs with higher concentrations of extracellular matrix (ECM) components compared with previously described methods. However, when seeded PGA scaffolds were cultured in perfusion bioreactors, they produced small constructs of poor quality. Investigation of the effect of medium flow rate on the PGA scaffolds showed that a low flow rate was needed at the beginning of the culture to enable the cells to form a framework onto which other synthesised elements could deposit. Applying a gradual increase in medium flow rate to PGA scaffolds cultured in perfusion bioreactors solved the shrinkage problem and produced constructs with quality similar to those produced using PGA??alginate scaffolds. A novel compression bioreactor that mimicked the physiological stimulation of cartilage by joint movement was constructed. Using this bioreactor, compressed constructs showed significantly higher wet weight and higher concentrations of GAG, total collagen and collagen type II compared with non-compressed constructs.

The influence of sea ice seeding on the northern Baltic Sea´s pelagic phytoplankton spring bloom was studied in a laboratory experiment in which microcosms mimicked sea conditions. On March 26th, 2018, samples (ice cores and seawater) were taken from land-fast ice at a coastal station in the Gulf of Bothnia. The seeding experiment lasted for 9 days, during which a 12:12 hours light:dark incubation took place. Four different treatments (two with ice and two without it) were set up in twelve incubated microcosms. Samples for analyses were taken on days 0, 3, 6 and 9. On day 0, measurements were carried out on four melted ice cores and on seawater. On the remaining days analyses were performed on the incubated microcosms. The measured variables were: chlorophyll a, phytoplankton abundance, bacterial abundance, conductivity and nutrients (TDN and TDP). The most abundant algal species were identified in a qualitative analysis. The obtained data were processed to calculate the average and standard deviations and to assess the existence of statistically significant differences among the treatments. A significant increase in chlorophyll a, phytoplankton and heterotrophic bacteria abundances was detected. A parallel decline in the nutrient concentrations was observed. A relationship between phytoplankton´s degree of influence and cell-size is suggested: cells > 3µm were more abundant in ice than in seawater, and the opposite tendency was appreciated for cells < 3 µm. My study shows that sea ice seeding can have a marked seeding effect on the size structure of the spring phytoplankton bloom.

As developers are increasingly creating more sophisticated applications, software systems are growing in both their complexity and size. When source code is easy to understand, the system can be more maintainable, which leads to reduced costs. Better structured code can also lead to new requirements being introduced more efficiently with fewer issues. However, the maintenance and evolution of systems can be frustrating; it is difficult for developers to keep a fixed understanding of the system’s structure as the structure can change during maintenance. Software module clustering is the process of automatically partitioning the structure of the system using low-level dependencies in the source code, to improve the system’s structure. There have been a large number of studies using the Search Based Software Engineering approach to solve the software module clustering problem. A software clustering tool, Munch, was developed and employed in this study to modularise a unique dataset of sequential source code software versions. The tool is based on Search Based Software Engineering techniques. The tool constitutes of a number of components that includes the clustering algorithm, and a number of different fitness functions and metrics that are used for measuring and assessing the quality of the clustering decompositions. The tool will provide a framework for evaluating a number of clustering techniques and strategies. The dataset used in this study is provided by Quantel Limited, it is from processed source code of a product line architecture library that has delivered numerous products. The dataset analysed is the persistence engine used by all products, comprising of over 0.5 million lines of C++. It consists of 503 software versions. This study looks to investigate whether search-based software clustering approaches can help stakeholders to understand how inter-class dependencies of the software system change over time. It performs efficient modularisation on a time-series of source code relationships, taking advantage of the fact that the nearer the source code in time the more similar the modularisation is expected to be. This study introduces a seeding concept and highlights how it can be used to significantly reduce the runtime of the modularisation. The dataset is not treated as separate modularisation problems, but instead the result of the previous modularisation of the graph is used to give the next graph a head start. Code structure and sequence is used to obtain more effective modularisation and reduce the runtime of the process. To evaluate the efficiency of the modularisation numerous experiments were conducted on the dataset. The results of the experiments present strong evidence to support the seeding strategy. To reduce the runtime further, statistical techniques for controlling the number of iterations of the modularisation, based on the similarities between time adjacent graphs, is introduced. The convergence of the heuristic search technique is examined and a number of stopping criterions are estimated and evaluated. Extensive experiments were conducted on the time-series dataset and evidence are presented to support the proposed techniques. In addition, this thesis investigated and evaluated the starting clustering arrangement of Munch’s clustering algorithm, and introduced and experimented with a number of starting clustering arrangements that includes a uniformly random clustering arrangement strategy. Moreover, this study investigates whether the dataset used for the modularisation resembles a random graph by computing the probabilities of observing certain connectivity. This thesis demonstrates how modularisation is not possible with data that resembles random graphs, and demonstrates that the dataset being used does not resemble a random graph except for small sections where there were large maintenance activities. Furthermore, it explores and shows how the random graph metric can be used as a tool to indicate areas of interest in the dataset, without the need to run the modularisation. Last but not least, there is a huge amount of software code that has and will be developed, however very little has been learnt from how the code evolves over time. The intention of this study is also to help developers and stakeholders to model the internal software and to aid in modelling development trends and biases, and to try and predict the occurrence of large changes and potential refactorings. Thus, industrial feedback of the research was obtained. This thesis presents work on the detection of refactoring activities, and discusses the possible applications of the findings of this research in industrial settings.

Seeds of six plant species of the genus Tillandsia (T.tricholepis, T. schiedeana, T. mauryan, T. sphaerocephala, T. streptocarpa and T. fasciculata) was planted on six different surfaces (acacia bark, coir, peat, polystyrene, nylon stocking and jute). In the first part of the experiment were recorded number of germinated seeds on individual surfaces. In the second part of the experiment had been observed growth or dying of germinated small plants for seven months. Statistical evaluation of the results showed that the most suitable surfaces for seeding and initial growth of Tillandsia are jute, nylon stocking and polystyrene.

Master of Science / Department of Agronomy / J. A. Dille / Weed control in grain sorghum has always presented a challenge to producers in the semi-arid Great Plains. Cultural control tactics such as narrowing of row spacings and increasing seeding rates can be effective control methods. The objective of this research was to determine the row spacing and seeding rates that maximizes yield while suppressing weeds. Grain sorghum row spacings of 25, 51, and 76-cm and seeding rates of 75,000, 100,000, 125,000, and 150,000 seeds ha[superscript]-1 were evaluated in Kansas at Beloit and Manhattan in 2013 and Beloit, Manhattan, and Hays in 2014. Grain sorghum growth and yield response were measured in response to natural weed communities. After evaluation, Beloit was considered a low weed pressure site while Manhattan and Hays were considered to be moderate and high weed pressure sites, respectively. Grain sorghum biomass was different while weed biomass was consistent across row spacings. Yield loss equations and profit functions were derived to determine the amount of grain yield and $ ha[superscript]-1 loss from each of the three locations. Yield and profit lost was greatest amongst weedy observations. Results indicated that grain sorghum grown on wide row spacings and seeding rates of 125,000 seeds ha[superscript]-1 out yielded all other treatments under a low weed pressure site (Beloit) and narrow row spacings out yielded wider spacings in moderate and high weed pressure sites (Manhattan and Hays). These results imply that a Kansas grain sorghum producer should evaluate potential weed pressure before determining a final row spacing and seeding rate.