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Small broomrape, a holoparasitic weed, is a relatively new weed introduction in the Pacific Northwest that has contaminated a limited number of red clover fields in Oregon. Greenhouse and field studies were conducted to evaluate small broomrape response to common crop and weed species in the Pacific Northwest. Host species in the greenhouse or field study included alfalfa, arrowleaf clover, carrot, celery, common vetch, crimson clover, lettuce, prickly lettuce, red clover, spotted catsear, subterranean clover, white clover, and wild carrot. False-host species included barley, birdsfoot trefoil, creeping bentgrass, cucumber, field corn, fine fescue, flax, Italian ryegrass, nasturtium, oat, orchardgrass, perennial ryegrass, snap bean, sugar pea, sunflower, sweet corn, tall fescue, tomato, and wheat. Non-host species included sugar beet and curly dock. The greenhouse polyethylene bag system provided a rapid and inexpensive screening for plant species host status to small broomrape. Germination and attachment to host roots are initiated by chemical exudates, that may change concentration in response to nutrient availability and microorganisms. Red clover was grown in varying concentrations of ammonium sulfate fertilizer with and without Rhizobium inoculation, and with small broomrape seeds. Neither Rhizobium inoculation nor ammonium concentration influenced the number of small broomrape attachments to red clover roots. A survey was conducted of red clover seed growers with small broomrape-contaminated fields in the Pacific Northwest. Red clover seed from six respondents were cleaned at the same cleaning facility, and the same respondents purchased their seed stock from this cleaning facility. Small broomrape was not identified in red clover fields prior to or during the first clover seed harvest of fall planted red clover in small broomrape-contaminated sites. / Graduation date: 2003

A high-efficiency gamma-ray counting system has been built at Los Alamos National Laboratory for use in analyzing nuclear forensics samples. This system consists of two clover high-purity germanium detectors and is surrounded by a thallium-doped sodium iodide annulus. Special precautions have been taken to ensure the system has a low background. The system is connected to XIA Pixie-4 fast digitizers and collects data in list-mode. This work is split into two main parts. The first part describes the proper steps and techniques to initialize the settings of a detector system connected to fast digitizers in order to optimize the system for resolution and throughput. The various counting modes for this particular system are described in detail, including the benefits and drawbacks of each mode. Steps are then shown to characterize the system by obtaining efficiency curves for various counting modes and sample geometries. Because of the close counting geometry involved with this system, true-coincidence summing factors must be calculated, and are done so in part by measuring the peak-to-total ratios of the system in its various counting modes across a wide energy range. The dead-time for the system can be complicated due to the multiple inputs of the system. Techniques for calculating the dead-time of multiple-detector systems are discussed. The second part of this work shows the system's usefulness in analyzing nuclear forensics samples, specifically irradiated enriched uranium. Three fission product parent-daughter pairs of different lifetimes are analyzed over a course of six months. The activities of each nuclide are calculated at each time step. Age dating techniques using the parent-daughter pairs are discussed, as well as the detection limits of each nuclide for a range of sample ages. Finally, avenues for further research are presented, as well as potential sources of error or uncertainty for this work. / text

Field studies were conducted in Ontario in 2009 and 2010 to determine the tolerance of winter wheat to herbicide-fungicide tank-mixtures, and the tolerance of winter wheat underseeded red clover to commonly used herbicides applied at three timings. Tank-mixtures including the fungicide tebuconazole caused injury at early and late timings, while mixtures including the herbicide bromoxynil/MCPA were most injurious when applied late in the season. Injury was transient with no yield reductions observed. MCPA/mecoprop/dicamba caused significant yield reductions when applied at normal and late timings, but did not reduce yield when applied early. The herbicides prosulfuron+bromoxynil and pyrasulfotole/bromoxynil were most injurious to underseeded red clover and reduced clover biomass regardless of application timing. Herbicides and herbicide-fungicide tank-mixtures applied early, during cold temperatures do not increase winter wheat or red clover sensitivity; the likelihood of injury is greatest when applications of these products occur late. / Grain Farmers of Ontario; Ontario Ministry of Agriculture, Food, and Rural Affairs; Agriculture Adaptation Council of Canada

This research assessed the seasonal effects of contrasting tillage and crop rotation systems on soil ammonia oxidizing bacteria (AOB) and archaea (AOA). Four different cropping systems under till and no-till were analyzed in a 30 year-old agricultural field trial. Samples were collected during the 2010 growing season at times corresponding with agronomic events. Nucleic acids were preserved in the field and subsequently analyzed by quantitative real-time polymerase chain reactions (qPCR). Tillage decreased AOB activity and abundance in the plow layer (0-15 cm) immediately after fall moldboard plow events, but observed AOB dynamics at other times suggest tillage had a long-term distribution effect across depth (0-30 cm). AOA abundance was significantly greater in no-till plots at all times indicating tillage had longer-term effects on these communities. Crop rotation had minimal effect on AOB and AOA, but there was a noted yield advantage for corn following wheat, regardless of tillage treatment. / OMAFRA Highly Qualified Personnel Program, NSERC

Most managed turfgrass species require frequent inputs to maintain an acceptable level of quality. Among these inputs, nitrogen (N) fertilization is usually the most limiting in terms of growth and development. However, N fertilization is also linked to non-point source (NPS) pollution. White clover (WC) is known for its ability to provide N when mixed into stands of turfgrass, and does not pose a threat for NPS pollution. Two field studies were designed to investigate the effects of WC inclusion in stands of cool-season turfgrasses. In the first field study, three cultivation techniques were examined for establishment of WC into preexisting turfgrass stands at three different seasonal timings. Scalping during the summer was seen as providing the highest WC populations, although scalping treatments also caused the most initial damage to the turfgrass. In the second field study, mixed stands of turfgrass and WC were examined for response to several weeks of traffic simulations, with WC withstanding the traffic events. Additionally, a greenhouse study was implemented to examine the effects of several commercial broadleaf herbicides on two WC varieties. Only 2,4-D was shown to be safe for application to both WC varieties, although Microclover did show tolerance to quinclorac applications.

Phosphate (P) supply is one of the major determining factors to plant productivity, since the element affects the growth and the development of plants. In response to Pdeficiency treatment, plants display alterations in root system architecture caused by changes in primary root (PR) and lateral root (LR) length and LR density. In this thesis, the root growth of the agronomically important legume, white clover (Trifolium repens L.) was found to be slightly stimulated in terms of PR length, LR number and total LR length when plants were grown in a P-deficient media (0.01 mM orthophosphate; Pi) when compared with plants grown in a P-sufficient media (1.00 mM Pi) when using a hydroponic growth system. When plants are grown in a P-sufficient media, treatment with 100 nM exogenous 1- aminocyclopropane-1-carboxylic acid (ACC) and exogenous auxin (5 nM 1- naphthylacetic acid, NAA) resulted in significant increases in white clover PR length, LR number and LR length. However, when ethylene action or auxin transport were inhibited using 300 ppm 1-methylcyclopropene (1-MCP) and 100 nM 1-Nnaphthylphthalamic acid (NPA), respectively, root growth was significantly reduced which suggests roles for ethylene and auxin in mediating white clover root growth. To examine the effects of these hormones on plants grown in P-deficient media, 100 nM ACC treatment significantly enhanced the stimulatory effects of growth on Pdeficient media only, while exposure of plants to P-deficiency alone was sufficient to significantly neutralise the inhibitory effects of 1-MCP on root growth. Hence, exposure to P-deficiency is proposed to increase either ethylene biosynthesis or ethylene sensitivity in white clover roots. In contrast, for plants grown in P-deficient media, treatment with 5 nM NAA significantly abolished the stimulation of white clover root growth observed with P-deficiency so it is proposed that exposure to Pdeficiency increases either auxin biosynthesis or auxin sensitivity, but the 5nM NAA concentration used was too high to stimulate root growth. Using DR5p::GUS transgenic white clover, auxin activity was found in the root tips and root primordia. Using these plants, it is suggested that P-deficient treatment and ACC treatment influenced white clover root growth through an increase in auxin sensitivity. Overall, ethylene and auxin are found to be essential in mediating white clover root growth in P-sufficiency, and also in mediating root responses to P-deficiency through changes in terms of the biosynthesis and the sensitivity of these two hormones.

Phosphate (P) supply is one of the major determining factors to plant productivity, since the element affects the growth and the development of plants. In response to Pdeficiency treatment, plants display alterations in root system architecture caused by changes in primary root (PR) and lateral root (LR) length and LR density. In this thesis, the root growth of the agronomically important legume, white clover (Trifolium repens L.) was found to be slightly stimulated in terms of PR length, LR number and total LR length when plants were grown in a P-deficient media (0.01 mM orthophosphate; Pi) when compared with plants grown in a P-sufficient media (1.00 mM Pi) when using a hydroponic growth system. When plants are grown in a P-sufficient media, treatment with 100 nM exogenous 1- aminocyclopropane-1-carboxylic acid (ACC) and exogenous auxin (5 nM 1- naphthylacetic acid, NAA) resulted in significant increases in white clover PR length, LR number and LR length. However, when ethylene action or auxin transport were inhibited using 300 ppm 1-methylcyclopropene (1-MCP) and 100 nM 1-Nnaphthylphthalamic acid (NPA), respectively, root growth was significantly reduced which suggests roles for ethylene and auxin in mediating white clover root growth. To examine the effects of these hormones on plants grown in P-deficient media, 100 nM ACC treatment significantly enhanced the stimulatory effects of growth on Pdeficient media only, while exposure of plants to P-deficiency alone was sufficient to significantly neutralise the inhibitory effects of 1-MCP on root growth. Hence, exposure to P-deficiency is proposed to increase either ethylene biosynthesis or ethylene sensitivity in white clover roots. In contrast, for plants grown in P-deficient media, treatment with 5 nM NAA significantly abolished the stimulation of white clover root growth observed with P-deficiency so it is proposed that exposure to Pdeficiency increases either auxin biosynthesis or auxin sensitivity, but the 5nM NAA concentration used was too high to stimulate root growth. Using DR5p::GUS transgenic white clover, auxin activity was found in the root tips and root primordia. Using these plants, it is suggested that P-deficient treatment and ACC treatment influenced white clover root growth through an increase in auxin sensitivity. Overall, ethylene and auxin are found to be essential in mediating white clover root growth in P-sufficiency, and also in mediating root responses to P-deficiency through changes in terms of the biosynthesis and the sensitivity of these two hormones.

The investigation in this thesis is divided into two parts. In the first part, the expression and accumulation of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO), the enzyme which catalyses the final step of ethylene biosynthesis in higher plants, is examined during exposure of white clover (Trifolium repens L.) to a water deficit. The second part of this thesis is focused on the identification and characterisation of a water-deficit-associated ACC synthase (ACS), the enzyme which catalyses the production of ACC. In the first part, two white clover varieties with differing sensitivity to water deficit, a drought-tolerant Tienshan ecotype and a drought-sensitive Grasslands Challenge cv. Kopu II cultivar were exposed to two water deficit treatments: one cycle of water deficit (designated non-prestressed; NPS) and a water deficit, a rehydration period and then a second water deficit treatment (designated pre-stressed; PS) in the New Zealand Climate Environment Laboratory (NZCEL). Treatments were terminated when the petiole elongation rate (PER) in the first fully-expanded leaf reached zero. Water relations, growth responses, the expression of the white clover ACO genes, TR-ACO1 TR-ACO2 and TR-ACO3 and the accumulation of two of the corresponding proteins, TR-ACO1 and TR-ACO2, were then examined. The soil water content (SWC) and leaf water potential (LWP) measured in both varieties and in both water deficit treatments declined progressively. The rate of decline in SWC and LWP was slower in the Tienshan ecotype with no difference between the NPS and PS treatments. However, the LWP in the Tienshan ecotype at the point at which the PER ceased was less negative (ca. -1.4 MPa) compared to Kopu (ca. -1.7 MPa). In addition, the decline in the PER differed between NPS- and PS-treated Kopu. In the NPS-treated Kopu, the PER was maintained at a high rate when plants were exposed to SWC above 18%, but declined sharply as the SWC declined further. However, in the PS-treated Kopu, the PER declined more progressively in a similar pattern to that determined for NPS- and PS-treated Tienshan. Expression of TR-ACO1 and accumulation of TR-ACO1 was observed in the apical structure of the stolon. As the water deficit progressed, no significant alteration in TR-ACO1 expression and TR-ACO1 protein accumulation was observed in the apical structures of both the NPS- and PS-treated Tienshan ecotype suggesting some degree of protection of the meristem tissues in this more drought-tolerant variety. However, a discernable decline in expression of TR-ACO1 and accumulation of TR-ACO1 protein was observed in the NPS-treated Kopu suggesting some degree of tissue injury in this more drought-susceptible variety. However, after the pre-stress (PS) treatment, no real changes in TR-ACO1 expression and TR-ACO1 protein accumulation were observed, in common with the observations for the NPS- and PS-treated Tienshan ecotype suggesting that meristem protection may now be occurring. The results suggest further that the pre-stress treatment of the more drought-susceptible Kopu may result in a degree of acclimation to the water deficit. For the first-fully expanded leaves, expression of two transcripts, TR-ACO2 and TR-ACO3 and accumulation of TR-ACO2 protein was monitored as the SWC decreased. The expression of TR-ACO2 and accumulation of TR-ACO2 decreased as the water deficit progressed in both the NPS- and PS-treated Tienshan ecotype and correlated with the decrease in PER. By contrast, in the NPS-treated Kopu, TR-ACO2 expression and TR-ACO2 protein accumulation increased, but again, after a period of pre-stress, TR-ACO2 expression and TR-ACO2 accumulation decreased, in common with the Tienshan ecotype. Again, the pre-stress treatment of the drought-susceptible Kopu may result in a degree of acclimation to the water deficit such that the responses become similar to those observed in the more drought-tolerant Tienshan ecotype. However, in both NPS- and PS-treated Tienshan and Kopu there was no significant alteration in the expression of TR-ACO3 in the first fully-expanded leaf. The expression of TR-ACO2 and TR-ACO3 and accumulation of TR-ACO2 protein were also observed in the second fully-expanded leaves (an older tissue). Again similar patterns in the expression of TR-ACO2 and TR-ACO3 and accumulation of TR-ACO2 protein were observed in both NPS- and PS-treated Tienshan and Kopu. In these leaves, expression of TR-ACO2 and accumulation of TR-ACO2 protein decreased as the water deficit progressed, but expression of TR-ACO3 increased as the water deficit decreased to less than 10%. These results suggest that responses of younger tissues (apical structure; first-fully expanded leaf) maybe the critical determinant for the tolerant (or otherwise) of white clover plants to water deficit. In the second part of this thesis, four ACS genes were identified from the Tienshan ecotype exposed to water deficit and designated TR-ACS-T. Three of these were similar to previously identified TR-ACS genes from Grasslands Challenge genotype 10F while the fourth was a novel gene designated TR-ACS4-T. TR-ACS4-T is 64%, 64% and 63% homologous to TR-ACS1-T, TR-ACS2-T and TR-ACS3-T, respectively in terms of nucleotide sequence. In the GeneBank database, TR-ACS4-T shares highly homology to ACC synthase sequences from a wide range of tissues including seedlings and fruit tissues, in addition to a high homology to ACS genes induced in auxin-, wounding- and ethylene-treated tissues. The pattern of TR-ACS4-T expression observed during leaf development suggests that the gene is expressed initially in the apical structures and in the newly initiated leaves, and then again in the later mature leaves and those at the onset of senescence. Expression decreases again during senescence. TR-ACS4-T expression is not altered by water deficit, but is induced by both ethylene and NAA treatment, but the auxin-induced TR-ACS4-T is mediated by ethylene treatment.

Phosphate (P) supply is one of the major determining factors to plant productivity, since the element affects the growth and the development of plants. In response to Pdeficiency treatment, plants display alterations in root system architecture caused by changes in primary root (PR) and lateral root (LR) length and LR density. In this thesis, the root growth of the agronomically important legume, white clover (Trifolium repens L.) was found to be slightly stimulated in terms of PR length, LR number and total LR length when plants were grown in a P-deficient media (0.01 mM orthophosphate; Pi) when compared with plants grown in a P-sufficient media (1.00 mM Pi) when using a hydroponic growth system. When plants are grown in a P-sufficient media, treatment with 100 nM exogenous 1- aminocyclopropane-1-carboxylic acid (ACC) and exogenous auxin (5 nM 1- naphthylacetic acid, NAA) resulted in significant increases in white clover PR length, LR number and LR length. However, when ethylene action or auxin transport were inhibited using 300 ppm 1-methylcyclopropene (1-MCP) and 100 nM 1-Nnaphthylphthalamic acid (NPA), respectively, root growth was significantly reduced which suggests roles for ethylene and auxin in mediating white clover root growth. To examine the effects of these hormones on plants grown in P-deficient media, 100 nM ACC treatment significantly enhanced the stimulatory effects of growth on Pdeficient media only, while exposure of plants to P-deficiency alone was sufficient to significantly neutralise the inhibitory effects of 1-MCP on root growth. Hence, exposure to P-deficiency is proposed to increase either ethylene biosynthesis or ethylene sensitivity in white clover roots. In contrast, for plants grown in P-deficient media, treatment with 5 nM NAA significantly abolished the stimulation of white clover root growth observed with P-deficiency so it is proposed that exposure to Pdeficiency increases either auxin biosynthesis or auxin sensitivity, but the 5nM NAA concentration used was too high to stimulate root growth. Using DR5p::GUS transgenic white clover, auxin activity was found in the root tips and root primordia. Using these plants, it is suggested that P-deficient treatment and ACC treatment influenced white clover root growth through an increase in auxin sensitivity. Overall, ethylene and auxin are found to be essential in mediating white clover root growth in P-sufficiency, and also in mediating root responses to P-deficiency through changes in terms of the biosynthesis and the sensitivity of these two hormones.