Light microscopy, low ionic strength solution culture and image analysis methods were used to make detailed measurements on root hair populations of different genotypes of white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.). A model of root hair population structure was developed and validated that will facilitate research on root hairs of these species. Diagrams were drawn of the root hair length and frequency on entire root systems. The distributions of root hairs on these diagrams often differed from textbook diagrams of root hairs because root hair length and frequency varied considerably along the root axis. The key issue examined was the response at species, population and genotype levels of root hair populations perturbed by aluminium and phosphate, and the implications of these responses for our understanding of the strategies adopted by plants growing in stressful environments. Demographic growth analysis gave the best understanding of the mechanisms of root hair population response to genetic variability, resource depletion and environmental perturbation. Root hair length seemed to be controlled by the individual root hair. However the number of root hairs appeared to be controlled by the root. Therefore it is the root that controls the distribution of the hairs on the root, and how this distribution is modified by perturbation. Root hair populations were shown to have strategies that were similar to their shoot system growth strategies-guerrilla for clover, phalangeal for ryegrass. The root and root hair systems, and shoot systems also demonstrated similar characteristics when the r and K strategy model was applied. At an ecosystem level, clover and ryegrass occupied the same orthogonal in the CSR (competitive-stress-ruderal) model. Therefore at a larger scale, these plants are able to coexist, but they do this by having different strategies at a species level. / Subscription resource available via Digital Dissertations only.

Light microscopy, low ionic strength solution culture and image analysis methods were used to make detailed measurements on root hair populations of different genotypes of white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.). A model of root hair population structure was developed and validated that will facilitate research on root hairs of these species. Diagrams were drawn of the root hair length and frequency on entire root systems. The distributions of root hairs on these diagrams often differed from textbook diagrams of root hairs because root hair length and frequency varied considerably along the root axis. The key issue examined was the response at species, population and genotype levels of root hair populations perturbed by aluminium and phosphate, and the implications of these responses for our understanding of the strategies adopted by plants growing in stressful environments. Demographic growth analysis gave the best understanding of the mechanisms of root hair population response to genetic variability, resource depletion and environmental perturbation. Root hair length seemed to be controlled by the individual root hair. However the number of root hairs appeared to be controlled by the root. Therefore it is the root that controls the distribution of the hairs on the root, and how this distribution is modified by perturbation. Root hair populations were shown to have strategies that were similar to their shoot system growth strategies-guerrilla for clover, phalangeal for ryegrass. The root and root hair systems, and shoot systems also demonstrated similar characteristics when the r and K strategy model was applied. At an ecosystem level, clover and ryegrass occupied the same orthogonal in the CSR (competitive-stress-ruderal) model. Therefore at a larger scale, these plants are able to coexist, but they do this by having different strategies at a species level. / Subscription resource available via Digital Dissertations only.

Light microscopy, low ionic strength solution culture and image analysis methods were used to make detailed measurements on root hair populations of different genotypes of white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.). A model of root hair population structure was developed and validated that will facilitate research on root hairs of these species. Diagrams were drawn of the root hair length and frequency on entire root systems. The distributions of root hairs on these diagrams often differed from textbook diagrams of root hairs because root hair length and frequency varied considerably along the root axis. The key issue examined was the response at species, population and genotype levels of root hair populations perturbed by aluminium and phosphate, and the implications of these responses for our understanding of the strategies adopted by plants growing in stressful environments. Demographic growth analysis gave the best understanding of the mechanisms of root hair population response to genetic variability, resource depletion and environmental perturbation. Root hair length seemed to be controlled by the individual root hair. However the number of root hairs appeared to be controlled by the root. Therefore it is the root that controls the distribution of the hairs on the root, and how this distribution is modified by perturbation. Root hair populations were shown to have strategies that were similar to their shoot system growth strategies-guerrilla for clover, phalangeal for ryegrass. The root and root hair systems, and shoot systems also demonstrated similar characteristics when the r and K strategy model was applied. At an ecosystem level, clover and ryegrass occupied the same orthogonal in the CSR (competitive-stress-ruderal) model. Therefore at a larger scale, these plants are able to coexist, but they do this by having different strategies at a species level. / Subscription resource available via Digital Dissertations only.

Light microscopy, low ionic strength solution culture and image analysis methods were used to make detailed measurements on root hair populations of different genotypes of white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.). A model of root hair population structure was developed and validated that will facilitate research on root hairs of these species. Diagrams were drawn of the root hair length and frequency on entire root systems. The distributions of root hairs on these diagrams often differed from textbook diagrams of root hairs because root hair length and frequency varied considerably along the root axis. The key issue examined was the response at species, population and genotype levels of root hair populations perturbed by aluminium and phosphate, and the implications of these responses for our understanding of the strategies adopted by plants growing in stressful environments. Demographic growth analysis gave the best understanding of the mechanisms of root hair population response to genetic variability, resource depletion and environmental perturbation. Root hair length seemed to be controlled by the individual root hair. However the number of root hairs appeared to be controlled by the root. Therefore it is the root that controls the distribution of the hairs on the root, and how this distribution is modified by perturbation. Root hair populations were shown to have strategies that were similar to their shoot system growth strategies-guerrilla for clover, phalangeal for ryegrass. The root and root hair systems, and shoot systems also demonstrated similar characteristics when the r and K strategy model was applied. At an ecosystem level, clover and ryegrass occupied the same orthogonal in the CSR (competitive-stress-ruderal) model. Therefore at a larger scale, these plants are able to coexist, but they do this by having different strategies at a species level. / Subscription resource available via Digital Dissertations only.

Light microscopy, low ionic strength solution culture and image analysis methods were used to make detailed measurements on root hair populations of different genotypes of white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.). A model of root hair population structure was developed and validated that will facilitate research on root hairs of these species. Diagrams were drawn of the root hair length and frequency on entire root systems. The distributions of root hairs on these diagrams often differed from textbook diagrams of root hairs because root hair length and frequency varied considerably along the root axis. The key issue examined was the response at species, population and genotype levels of root hair populations perturbed by aluminium and phosphate, and the implications of these responses for our understanding of the strategies adopted by plants growing in stressful environments. Demographic growth analysis gave the best understanding of the mechanisms of root hair population response to genetic variability, resource depletion and environmental perturbation. Root hair length seemed to be controlled by the individual root hair. However the number of root hairs appeared to be controlled by the root. Therefore it is the root that controls the distribution of the hairs on the root, and how this distribution is modified by perturbation. Root hair populations were shown to have strategies that were similar to their shoot system growth strategies-guerrilla for clover, phalangeal for ryegrass. The root and root hair systems, and shoot systems also demonstrated similar characteristics when the r and K strategy model was applied. At an ecosystem level, clover and ryegrass occupied the same orthogonal in the CSR (competitive-stress-ruderal) model. Therefore at a larger scale, these plants are able to coexist, but they do this by having different strategies at a species level. / Subscription resource available via Digital Dissertations only.

Master of Science / Department of Entomology / John C. Reese / The soybean aphid, Aphis glycines Matsumura, is a pest of soybean, Glycine max (L.) Merr. Studies to find control methods were initiated in 2000 when it was first detected in the United States. Aphis glycines can reduce yields by as much as 50%, and vectors several viral diseases. Plant resistance to A. glycines is one important component of integrated control. In the first study, reproduction of A. glycines was compared on 240 soybean entries. Eleven had fewer nymphs produced compared with two susceptible checks (KS4202 and Pioneer® 95B15). Antibiosis and antixenosis were assessed in no-choice and choice tests, respectively. Nine entries showed moderate antibiosis and the other two (K1639 and Pioneer® 95B97) showed strong antibiosis and antixenosis as categories of resistance to A. glycines. In the second study, chlorophyll loss was estimated in no-choice tests on infested and uninfested leaves of KS4202. The minimum combined number to detect significant chlorophyll loss was 30 aphids confined for 10 days. Using this number, seven resistant entries found in the first study were evaluated. There was no significant chlorophyll reduction between infested and uninfested leaves of five of the resistant entries (K1621, K1639, 95B97, Dowling and Jackson). Jackson and Dowling had a significantly lower percentage loss than the susceptible checks. In the third study, assessment of feeding behavior of A. glycines was compared and recorded for 9 h on four resistant entries and KS4202. The average time needed to reach the first sieve element phase by A. glycines was 3.5 h in KS4202 while in the resistant entries it was 7.5 h, and the total duration in this phase was longer than an hour in KS4202, and only two to seven minutes in the resistant entries. These data suggest that phloem tissues in the resistant plants change feeding behavior. However, aphids first reached the xylem phase and then the sieve element phase, and the time that aphids spent ingesting xylem sap was not different among all entries; therefore, it is possible that xylem sap in the resistant entries may contain toxic substances that alter aphid behavior and restrain further activities on the sieve element phase.

Master of Science / Department of Electrical and Computer Engineering / Sanjoy Das / Stephen M. Welch / Multi-objective optimization problems deal with finding a set of candidate optimal solutions to be presented to the decision maker. In industry, this could be the problem of finding alternative car designs given the usually conflicting objectives of performance, safety, environmental friendliness, ease of maintenance, price among others. Despite the significance of this problem, most of the non-evolutionary algorithms which are widely used cannot find a set of diverse and nearly optimal solutions due to the huge size of the search space. At the same time, the solution set produced by most of the currently used evolutionary algorithms lacks diversity. The present study investigates a new optimization method to solve multi-objective problems based on the widely used swarm-intelligence approach, Particle Swarm Optimization (PSO). Compared to other approaches, the proposed algorithm converges relatively fast while maintaining a diverse set of solutions. The investigated algorithm, Partially Informed Fuzzy-Dominance (PIFD) based PSO uses a dynamic network topology and fuzzy dominance to guide the swarm of dominated solutions. The proposed algorithm in this study has been tested on four benchmark problems and other real-world applications to ensure proper functionality and assess overall performance. The multi-objective gene regulatory network (GRN) problem entails the minimization of the coefficient of variation of modified photothermal units (MPTUs) across multiple sites along with the total sum of similarity background between ecotypes. The results throughout the current research study show that the investigated algorithm attains outstanding performance regarding optimization aspects, and exhibits rapid convergence and diversity.

Doctor of Philosophy / Agronomy / Allan K. Fritz / Bikram S. Gill / Gary M. Paulsen / Post-anthesis high temperature stress in wheat (Triticum aestivum L.) is a major cause of yield reduction. This process results in the loss of viable leaf area and a decrease in green leaf duration ultimately causing a yield loss. The objectives of this study were to (i) phenotype a recombinant inbred line population for heat tolerance traits, (ii) understand the genetic basis of heat tolerance by mapping quantitative trait loci (QTL) linked to yield-related traits under high temperature, (iii) model stay-green under high temperature stress and map the QTL linked to stay-green parameters, and (iv) validate the markers linked to QTL under field conditions. A filial6:7 (F6:7) recombinant inbred line (RIL) population was developed by crossing Ventnor, a heat-tolerant white winter wheat with Karl 92, a relatively heat susceptible hard red winter wheat. From 10 DAA to maturity, the treatments of optimum temperature or high temperature stress (30/25°C) were imposed on the RILs. The traits measured included grain filling duration (GFD), kernels per spike, thousand kernel weight (TKW), and grain filling rate (GFR). The stay-green traits calculated were: i) time between 75% and 25% green, ii) maximum rate of senescence, iii) time to maximum rate of senescence, and v) percent green at maximum senescence. Genetic characterization was performed using microsatellite (SSR), amplified fragment length polymorphism (AFLP) and a sequence tag site (STS) markers. GFD was positively correlated with TKW and negatively with GFR and maximum rate of senescence. Principle component analysis (PCA) showed kernels per spike, maximum rate of senescence, and TKW accounted for 98% of total variability among the genotypes for heat tolerance. The most significant QTL for yield traits co-localized with marker Xgwm296 for TKW, Xgwm356 for kernels per spike, and Xksum61 for GFR. The QTL for stay-green traits co-localized with markers P41/M62-107 on Chromosome 2A, Xbarc136 on Chromosome 2D, P58/MC84-146 on Chromosome 3B, P58/M77-343 on Chromosome 6A, and. P58/MC84-406 on Chromosome 6B. These results indicate that increased green leaf area duration has a positive effect on the grain yield under high temperature. Once the kernels per spike are established, GFD and TKW can be used as selection criteria for post-anthesis heat-tolerance.