Browsing by Author "Pilon-Smits, Elizabeth, committee member"

Now showing 1 - 15 of 15

Open Access
A new woody perspective on copper homeostasis: systemic copper transport and distribution, effect of copper on lignification, and water transport in hybrid poplar
(Colorado State University. Libraries, 2022) Hunter, Cameron Ross, author; Pilon, Marinus, advisor; Gleason, Sean, advisor; Pilon-Smits, Elizabeth, committee member; Argueso, Cristiana, committee member; Bush, Daniel, committee member
Copper (Cu) is an essential micronutrient for plants. Chapter 1, as background for this dissertation, reviews the functions and homeostasis of Cu. We know at the cellular level how Cu is delivered to target proteins in the chloroplasts, thus explaining in a large part why Cu deficient plants have reduced photosynthetic capacity. However, Cu is also a cofactor of lignin polymerization enzymes that affect cell wall and xylem structures required for water and mineral transport. How Cu deficiency affects water transport, mineral nutrition, and photosynthesis at a whole plant level is underexplored. To address this knowledge gap, we used hybrid white poplar as a model. In chapter 2, a stable isotope method to trace Cu movement in poplar tissues was coupled with analysis of photosynthesis and stomatal conductance. Upon resupply of Cu, priority targets identified were stems and younger leaves which recovered quickly and was associated with higher stomatal conductance. In chapter 3, the effect of Cu deficiency on the elemental composition of leaves and stems of different age were analyzed. Interestingly, tissue type and age, as well as Cu deficiency, were found to all significantly affect within-plant nutrient partitioning patterns. In chapter 4, the effects of Cu deficiency on cell wall chemical composition and water transport traits were determined. Although Cu deficiency strongly affected cell wall chemistry, it did not significantly impact hydraulic capacity nor the density and size of xylem vessels in stems. However, Cu deficiency resulted in markedly stiffer mesophyll cell walls, possibly arising from changes to cell wall chemistry or structure. Together, these results, as discussed in chapter 5, indicate that although xylem lignification was adversely affected by Cu deficiency, the water transporting vessels remained largely unaffected, thus allowing efficient recovery. This work opens new avenues to explore the effects of plant nutrition on whole-plant physiology and function.
Open Access
Characterization of a synthetic signal transduction system
(Colorado State University. Libraries, 2012) Albrecht, Tessa, author; Medford, June, advisor; Bush, Daniel, committee member; Pilon-Smits, Elizabeth, committee member; Leach, Jan, committee member
The Medford laboratory has developed a synthetic signal transduction system linking exogenous perception of a particular ligand to a transcriptional response. One application of this system is to produce plants that sense and respond to a specific ligand. The system was designed based on evolutionary conservation of histidine kinase signaling and uses bacterial components adapted to function in plants. The synthetic signaling system is responsive to extracellular ligand perception by a wild-type or modified ribose binding protein (RBP) scaffold. Upon ligand binding, RBP binds and activates a synthetic fusion histidine kinase made from the extracellular portion of the bacterial chemotactic receptor Trg and the cytoplasmic portion of the bacterial phosphate sensor PhoR. Activated Trg-PhoR transmits a phosphate signal to the bacterial response regulator PhoB. Upon phosphorylation PhoB translocates into the nucleus of a plant cell and activates transcription of the response gene(s). In addition to receiving a phosphate signal from Trg-PhoR, PhoB can be activated by exogenous cytokinin application suggesting that components of the cytokinin signaling pathway can interact with PhoB. Elimination or reduction of the interaction with cytokinin signaling components allows production of a more reliable signaling system. One goal of the following work was to reduce the interaction of PhoB with endogenous cytokinin signaling components. I attempted to identify a mutant form of PhoB that does not interact with cytokinin signaling components yet maintains function with the synthetic signaling system. I screened six different rationally selected PhoB mutants in plants for reduced response to exogenous cytokinin application. I concluded that a different approach will be needed to successfully reduce interaction with cytokinin signaling components. Another goal of this work was the identification cytokinin signaling components that interact with PhoB, possibly revealing a means to eliminate the interaction. I attempted to functionally express selected cytokinin signaling components in a bacterial testing system. After several failed cloning strategies, I conclude that the cytokinin sensor histidine kinase, AHK4, may be toxic and/or unstable in bacteria and expression of alternative genes will be needed to identify cytokinin signaling components that interact with PhoB. Additional work described here includes the independent testing of two computationally designed RBPs; one reported to bind the environmental pollutant methyl tert-butyl ether and the other reported to bind the explosive trinitrotoluene, for ligand dependent activation of the synthetic signaling system. These results show that the computationally designed RBPs do not function in a reliable manner and lead to the production of a detector plant using wild-type RBP to activate the synthetic signaling system that enables further analysis of the system components in plants.
Open Access
Characterizing acclimation of pansy and petunia to CO₂ enrichment for controlled environment production
(Colorado State University. Libraries, 2021) McKinney, David Wayne, author; Craver, Joshua, advisor; Pilon-Smits, Elizabeth, committee member; Bauerle, Bill, committee member
While crops often respond immediately to enriched CO2 concentrations (e.g., increased photosynthesis), this initial response is often not sustained throughout production, reducing the benefit of this input. For horticulture species, the timing and extent of these acclimation responses is still widely uncertain. Therefore, the objective of this research was to determine species-specific acclimation responses to enriched CO2 concentrations for pansy (Viola ×wittrockiana 'Matrix Blue Blotched Improved') and petunia (Petunia ×hybrida 'Dreams Midnight) during both propagation and finishing. To investigate the effects of enriched CO2 concentrations on pansy and petunia during finishing production, seedlings were transplanted into 11.5-cm pots and placed in growth chambers with air temperature, relative humidity, and radiation intensity setpoints of 21 °C, 55%, and 250 µmol∙m–2∙s–1, respectively. Carbon dioxide treatments were established using the two growth chambers with setpoints of either 400 (ambient) or 1000 μmol·mol–1 (enriched) maintained during a 16-h photoperiod. In addition to data collected through destructive harvest, rate of photosynthesis (A) in response to increasing internal leaf CO2 concentration (A-Ci) and ambient CO2 concentration (A-Ca) were measured weekly with a portable leaf photosynthesis system at saturating (A-Ci; 1000 µmol∙m–2∙s–1) or production (A-Ca; 250 µmol∙m–2∙s–1) radiation intensities. For both pansy and petunia, plants grown under the enriched CO2 concentration produced higher total shoot dry mass compared to ambient after 4 weeks. However, decreased maximum rate of photosynthetic electron transport (Jmax), maximum rate of Rubisco carboxylase (Vcmax), and similar photosynthesis at operating Ci concentration were observed under the enriched CO2 concentration after 4 weeks. Additionally, A measured at 1000 and 400 μmol·mol–1 was lower for both pansy and petunia grown under the enriched compared to ambient CO2 concentration based on A-Ca responses after 1 week, further indicating quick physiological acclimation to this input. This indicates little benefit of elevated CO2 to increase plant quality during the finishing stage of production in pansy and petunia, however there is possible marginal benefit due to increased biomass with no effect on overall plant size. To evaluate the impact of CO2 enrichment at varying timing and duration during propagation, pansy and petunia seeds were sown in 128-cell trays and placed in growth chambers with air temperature, relative humidity, and radiation intensity setpoints of 21 °C, 55%, and 250 µmol∙m–2∙s–1, respectively. Carbon dioxide treatments were established using the two growth chambers with setpoints of either 400 (ambient) or 1000 μmol·mol–1 (enriched) maintained during a 16-h photoperiod. Treatments consisted of seedlings grown for 28 days at ambient (Amb28), 28 days at elevated (Elv28), 14 days at ambient then 14 days at elevated (Amb14:Elv14), and 14 days at elevated then 14 days at ambient CO2 concentration (Elv14:Amb14). Harvest data was collected weekly, and four weeks after germination seedlings were transplanted into the greenhouse to determine impacts on finishing quality and flowering. Pansy and petunia produced higher total dry mass (roots + leaves + stem) under Elv28 and Amb14:Elv14 compared to Amb28 after 4 weeks, but showed no difference in leaf area. Additionally, plants grown under Elv28 and Amb14:Elv14 produced higher leaf mass area than Amb28 and Elv14:Amb14 for both species. Pansy showed decreased days to flower under Elv28, but no difference in biomass or size after transplant into the greenhouse. Therefore, elevated CO2 during seedling production may influence days to flower but does not contribute to growth rate long term after transplant. Likewise, similar morphological responses can be achieved with elevated CO2 being applied during the last two weeks of seedling production compared to elevation throughout the propagation stage. These results provide useful information regarding the timing and extent of physiological acclimation in response to enriched CO2 concentrations for pansy and petunia. However, due to physiological acclimation potentially occurring within one week of treatment initiation, additional research is needed to best understand how this input can be further optimized for controlled environment production.
Open Access
Copper transport into the chloroplast and its implications for copper homeostasis in Arabidopsis thaliana
(Colorado State University. Libraries, 2012) Tapken, Wiebke, author; Pilon, Marinus, advisor; Chisholm, Stephen, committee member; Pilon-Smits, Elizabeth, committee member; Reddy, Anireddy S. N., committee member
Copper (Cu) is an essential micronutrient for most aerobic organisms including plants. It is present as Cu+ or Cu2+, which makes it an ideal cofactor for enzymes involved in processes such as photosynthesis and respiration. Plant cuproproteins are almost ubiquitously found in every cell compartment. The blue Cu protein plastocyanin (PC) is believed to bind the majority of Cu ions in green tissues and is essential for higher plants. Cu reaches the thylakoid lumen through the activity of two P1B-type ATPases called PAA1/HMA6 and PAA2/HMA8 (P-type ATPase of Arabidopsis/Heavy-metal ATPase), which are located in the inner chloroplast envelope and the thylakoid lumen respectively. Under Cu limiting conditions, plants have been suggested to prioritize cellular Cu to PC to ensure adequate photosynthesis. This process involves the post-transcriptional down-regulation of seemingly less essential cuproproteins through the activity of a single transcription factor called SPL7 (SQUAMOSA promoter binding protein-like7). The first chapter reviews Cu homeostasis in plants. The research presented in the three experimental chapters of this dissertation is aimed to determine the role of the chloroplast in Cu homeostasis of Arabidopsis thaliana. I report a novel SPL7-independent and chloroplast-specific regulation of the thylakoid-localized Cu transporter PAA2/HMA8. The transporter is most abundant in the absence of Cu and is turned over at higher chloroplastic Cu concentrations. PAA2/HMA8 abundance in Cu deficiency is furthermore controlled by the presence of PC, because in a pc mutant PAA2/HMA8 abundance is always low. The regulation of the transporter likely serves as a checkpoint for the Cu requirements of the thylakoid lumen. I identified two components of the stroma-localized Clp protease (Caseinolytic peptidase) which are involved in PAA2/HMA8 turnover. The Cu status of these mutants is not affected, decreasing the likelihood of a secondary affect of Cu on PAA2/HMA8 in these plants. In the last experimental chapter I summarize relevant results that further describe and characterize PAA1 and PAA2. Most notably, Arabidopsis encodes for a splice-form of PAA1. This much smaller fragment is expressed with a chloroplast targeting sequence and could potentially function as a stromal Cu chaperone.
Open Access
Don't cry over spilled water: identifying risks and solutions for produced water spills
(Colorado State University. Libraries, 2017) Shores, Amanda Rose, author; Laituri, Melinda, advisor; Butters, Gregory, committee member; Pilon-Smits, Elizabeth, committee member; Gooseff, Michael, committee member
Resource requirements and future energy generation requires careful evaluation, particularly due to climate change and water scarcity. This thesis discusses one aspect of energy generation linked to water; oil-and-gas extraction and the large volumes of waste water produced, otherwise known as "produced water". This research focuses on surface spills of produced water, their ramifications, safeguards against groundwater contamination at spill sites and potential remediation strategies. Produced water contains a variety of contaminants that include the group of known toxins, BTEX (benzene, toluene, ethylbenzene and xylene), and high salt concentrations. A combination of factors such as large volumes of generated produced water, the need for storage and transportation across large distances and the toxic-and-mobile nature of produced water constituents creates risks for spills that can pollute groundwater. Spills occur regularly, particularly in Weld County, Colorado, where the demand for natural gas is high. To answer spill-related hypotheses, a multitude of methodology were employed: modeling, greenhouse experimentation, gas chromatography and summarization of spill reports and statistical analyses. Using publicly available spill data, this research found that the frequency of oil-and-gas related spills and the average spilled volume has increased in Weld County from 2011–2015. Additionally, the number of spills that have resulted in groundwater contamination has increased in the area. By focusing on the oil-and-gas operators responsible for these spills, a linear relationship was found between the volumes of oil-and-gas produced compared to the volumes of produced-water generated. However, larger oil-and-gas producers did not show a linear relationship between oil-and-gas produced and produced-water generated, such that larger producers were more efficient and generated less water per unit of energy. So while scale-up efficiency seems to exist for produced-water generation, no mitigation of spill volume would be obtained by utilizing larger producers. Regardless of which operator was responsible for the spill, the groundwater depth at a spill site significantly predicted when a spill would result in groundwater contamination. This result was also validated though modeling; shallow depths to groundwater as well as larger spill volumes and coarse soil textures contributed to higher concentrations of groundwater contamination. Previous research has shown that a large fraction of spills occur at well pads. Our results suggest that fracking-site selection should preclude areas where the groundwater is shallow and soil is coarsely textured. Additionally, precautions should be taken to reduce the volume of spilled produced water to reduce the risk of groundwater contamination. This research additionally sought to reduce contaminant migration in soils towards groundwater at produced-water spill sites. In a greenhouse study it was shown that foxtail barley (Hordeum jubatum) and perennial ryegrass (Lolium perenne), can tolerate high salt concentrations in produced water while taking up minute levels of BTEX. The presence of plants changed the concentration of BTEX and naphthalene in the soil, but the direction of the change depended upon the particular plant and varied across contaminants. Additionally, the roots of either species saw no decrease of biomass upon exposure to BTEX and salt but shoots biomass was significantly reduced for foxtail barley. These results suggest that these grasses would not be capable of addressing large concentrations of BTEX at spill sites; however, these plants would be useful near well pads that regularly experience smaller spills, thus being able to tolerate spills while continually removing small amounts of BTEX in the soil. In conclusion, this thesis sought to identify holistic tools for produced-water spill prevention, mitigation and remediation to lessen environmental and health concerns while creating minimal disturbance to the natural landscape. The results lend themselves to important management information applicable to Weld County, CO but with lessons that others can draw upon elsewhere. This dissertation highlights areas for improved regulation and best management practices that can preemptively reduce the risk for groundwater contamination from produced water spills.
Open Access
Enhancing herbaceous perennial stock production through the application of plant growth regulators for Heuchera sanguinea 'Snow Angel' and Zauschneria garrettii ‘PWWGO1S' Orange Carpet®
(Colorado State University. Libraries, 2018) Markovic, Sean, author; Klett, Jim, advisor; Newman, Steven, committee member; Pilon-Smits, Elizabeth, committee member
Commercial growers throughout the Rocky Mountain Region have an increased commercial demand for sustainable herbaceous perennial plants. Greenhouse production for these adaptable perennials has resulted in problems with stock plant management and propagation. The objective of this study was to determine the efficacy for increased vegetative growth of three dissimilar plant growth regulators applied as foliar sprays on the vegetative growth of Heuchera sanguinea 'Snow Angel' and Zauschneria garrettii 'PWWGO1S' ORANGE CARPET® propagation stock plants in number one (2.84L) containers. Three chemical plant growth regulators were applied at two different rates: 1) Ethephon (2-chloroethyl Phosphonic Acid) (200 and 400 mg·L–1 (ppm)) (Verve, Nufarm Americas, Inc., Alsip, IL), 2) 6-benzylaminopurine (250 and 500 mg·L –1) (Configure; Fine Agrochemicals Limited, Worcester, U.K.), and 3) Gibberellins A4A7 (GA) & N-(phenylmethyl)-1H-purine 6-amine (50 and 100 mg·L–1) (Fascination; Valent USA Corp., Fresno, CS). Twelve replications of the two taxa were evaluated every month for a period of four months for plant height, width, number of cuttings, and fresh & dry weight of the cuttings. This study was replicated twice, the first experiment was performed from November 2016 to March 2017, and the second experiment was performed from August 2017 to December 2017. The two experiments conducted at different times of the year gave an indication of a better time of year for stock production of these two herbaceous perennials. Heuchera performed better in the first experiment from November to March. The Zauschneria plants performed better during the second experiment from August to December. Heuchera plants that received Fascination (A4A7 (GA) & N-(phenylmethyl)-1H-purine 6-amine) treatments at 50 and 100 mg·L–1 and Configure (6-benzylaminopurine) at 400 mg·L–1 concentrations resulted in 17%, 22%, and 20% more cuttings taken than control plants. Both concentrations of Ethephon treated Heuchera plants were statistically similar to control plants. Zauschneria plants that received Fascination (A4A7 (GA) & N-(phenylmethyl)-1H-purine 6-amine) treatments at 50 and 100 mg·L–1and Configure (6-benzylaminopurine) at 200 mg·L–1 concentrations resulted in 14%, 16%, and 10% more cuttings, respectively. However, Zauschneria plants that received Fascination (A4A7 (GA) & N-(phenylmethyl)-1H-purine 6-amine) treatments at 50 and 100 mg·L–1 had a decrease of 13% and 14% for the fresh weight of cuttings taken when compared to the control. Configure (6-benzylaminopurine) treatments also resulted in a visual decrease in reproductive growth. The different applications of the plant growth regulators resulted in a wide variety of cutting sizes and water content; this is based on the differences seen per treatment in the fresh and dry weights collected. A secondary rooting study was conducted after each stock plant experiment. Cuttings were harvested from each treatment combination after four weeks; May 16, June 13, and July 11, 2017 for the first experiment and January 11, February 8, and March 1, 2018 for the second experiment. Cuttings were taken at the same time of day, in the morning, and stuck in trays of 98 or 72 cells filled with Jiffy® Preforma media and placed under mist with bottom heat at a temperature of 18.3 or 23.9 degrees Celsius for Heuchera and Zauschneria respectively. Rooting percentages and number of visible roots were then collected every week for four weeks. Rooting of the two taxa resulted in no statistical differences observed between the treatments and the control. This gave the indication that the use of plant growth regulators during stock plant production would not result in decrease rooting of the harvested cuttings. In conclusion, the use of plant growth regulators resulted in increases in propagation material produced by stock plants of both taxa. A Fascination (A4A7 (GA) & N-(phenylmethyl)-1H-purine 6-amine) treatment between 50 and 100 mg·L–1 is recommended in Heuchera sanguinea stock plant production for its increase in cuttings available at each harvest event. A Configure (6-benzylaminopurine) at 200 mg·L–1treatment is recommended for Zauschneria garrettii stock plant production due to the increase in quality vegetative propagation material.
Open Access
Impacts of LED interlighting on the growth, yield, and quality of hydroponic greenhouse tomatoes
(Colorado State University. Libraries, 2018) Burns, Tara Nicole, author; Uchanski, Mark, advisor; Pilon-Smits, Elizabeth, committee member; Newman, Steven, committee member
Recent technological advances have lead to light emitting diode (LED) lights becoming more readily available. They are becoming established as a way to supplement light in controlled environment crop production and are typically used as a top light. Due to their unique characteristics, LED lighting infrastructure and the lights themselves can also be placed within the canopy (interlighting bars); a location that has typically been hard to reach with traditional high-pressure sodium or ceramic discharge lamps. Currently, there is little research on the overall effects of interlighting on plant growth and productivity. Therefore, four studies were conducted to measure the impacts of interlighting on the growth of hydroponically grown greenhouse tomatoes. Interlighting was evaluated for a 16:8 photoperiod (light:dark) under both naturally increasing and decreasing daylengths. Tomato plants were grown in perlite and trained to a single leader on an overhead support system. Flowers were hand pollinated twice a week to ensure fruit set. Data collected included vegetative biomass, individual fruit weight, total fruit yield, soluble solids content, pH, and leaf gas exchange to assess tomato vegetative and reproductive growth and physiological parameters. In addition, the photosynthetically active radiation (PAR) output of the interlighting was measured to create a light distribution map. Lastly, a distance experiment was conducted to measure the effects of the proximity of the interlighting bars on early tomato vegetative growth. Across three experiments we observed that interlighting significantly increased gas exchange measurements (i.e. photosynthetic rate) in individual lighted leaves, however, overall vegetative growth and fruit yield did not increase. Although individual leaves responded to the additional light resource located in the canopy, it did not significantly increase overall yield on quality of greenhousegrown tomato fruits.
Open Access
Increased chlorophyll efficiency of dark-adapted camellia foliage when treated with chlorine dioxide or hydrogen dioxide and blended with a non-ionic surfactant
(Colorado State University. Libraries, 2013) Hammack, Heather Nicole, author; Newman, Steven E., advisor; Qian, Yaling, committee member; Pilon-Smits, Elizabeth, committee member
Phytophthora ramorum is a major risk to interstate trade of nursery stock. This work focused on chemical oxidant chemistry as a disinfectant of nursery grown camellia plants. Disinfection of nursery stock is crucial for shipping, but the impact on plant health and phytotoxic responses are also important. To determine plant stress responses to applied chemical oxidants, we measured chlorophyll activity (PSII maximum quantum efficiency) as measured by Fv/Fm values on dark-adapted camellia plants. Data were collected using a Li-COR 6400XT leaf chamber fluorometer (Li-COR, Lincoln, NE) to evaluate the potential phytotoxicity of camellia to foliar applied chlorine dioxide (ClO2) and hydrogen dioxide (H2O2), with or without sarcosinate surfactant with consecutive spray applications. Chlorophyll activity (Fv/Fm) of dark adapted foliage was greater when ClO2 and H2O2 were applied with sarcosinate surfactant to camellia foliage compared to treatments not containing sarcosinate surfactant. Chlorophyll activity decreased with increasing concentrations of ClO2 without sarcosinate. Higher Fv/Fm across seven measurement intervals were observed in ClO2 treatments compared to H2O2 treatments at the same concentration. Visual injury of camellia foliage increased with each of the five subsequent spray applications; however, foliar injury did not exceed a marketable threshold for most treatments, until after four consecutive spray applications at 400 mg·L-1 ClO2, with or without surfactant. This study demonstrated that Electro-BioCide at a rate predicted to eradicate Phytophthora ramorum (200 mg·L-1) should not visually damage camellia plants until after five consecutive spray applications. These findings indicate that Electro-BioCide has the potential to be implemented as a preventative foliar treatment for defense against foliar plant pathogens, without concern for detriment to plant health.
Open Access
Inventory dynamics and soil factors affecting soil-to-plant ¹³⁷Cs transfers in Fukushima forest ecosystems
(Colorado State University. Libraries, 2020) Zhang, Jian, author; Johnson, Thomas, advisor; Brandl, Alexander, committee member; Sudowe, Ralf, committee member; Pilon-Smits, Elizabeth, committee member
The objective of this study was to understand the soil factors affecting soil-to-plant transfer factors in understory plant species as well as their contribution to the total 137Cs inventory in aboveground biomass within the Fukushima forest ecosystem. Radiocesium contamination from the March 2011 accident at the Fukushima Da-ichi Nuclear Power Station (FDNPS) was initially deposited on the forest canopies with deposition into the soil occurring over the next few years through litterfall and precipitation. Measurements taken from the Yamakiya site in 2014 show that the contribution of understory plants to the total inventory of radiocesium in aboveground biomass was very low compared to the dominant Japanese cedar trees. However, measurements were not taken in other affected sites within Fukushima prefecture as well as potential change in concentrations of radiocesium in understory biomass since 2014. Data for evaluating the transfer factors was obtained through sampling of soil and understory plants at the Yamakiya, Tsushima, Tomioka, Okuma, and Yokomuki sites inside Fukushima Prefecture. Both 134Cs and 137Cs measurements were collected, however 134Cs concentrations were negligible compared to 137Cs so only 137Cs data was considered. 137Cs content was determined using gamma spectroscopy of the soil and plant samples and to find the concentration of bioavailable 137Cs within the root profile of the understory plants as well as 137Cs concentration within the understory plant itself. The soil and plant 137Cs concentration was used to determine the soil-to-plant uptake factors for the sampled understory species as well as the contribution of the understory plants to the total 137Cs inventory in aboveground biomass. The effect of soil exchangeable [K+], exchangeable [Cs+], exchangeable 137Cs activity concentration, total 137Cs activity concentration, and pH on 137Cs uptake by understory plants was determined through the soil-to-plant uptake factors at the various sample sites. The same data was used to find the 137Cs deposition in the soil, 137Cs inventory in Yamakiya, and patterns between plant activity concentration between plant species. Soil measurements showed a logarithmic decrease in 137Cs activity concentration with decreasing soil depth. Measurements also supported a 4.39 year effective half-life using GIS and Nuclear Regulatory Authority data, however using IER data a radiological half-life of 30.17 years was supported instead. The majority of 137Cs inventory in Yamakiya was found to be in soil (80.54%) and trees (18.52%) with understory plants making up a negligible contribution. This contribution by trees was much higher than the one found in previous years. For understory plants, it was found that there are higher 137Cs activity concentrations in the more metabolically active portions of the plants. 137Cs was a significant contributing factor across all understory plant species in predicting the soil to plant transfer factors. The ability to properly estimate the activity concentration of understory plants using only the one soil factor can contribute to faster estimation of potential 137Cs concentrations in plants or uptakes by herbivores in areas contaminated by 137Cs. The further understanding of 137Cs dynamics in forest ecosystems will assist in creation of a long-term forest radiation contamination management strategy.
Open Access
Phytohormone effect on Pterocephalus depressus stock plant productivity and phytohormone accumulation and movement
(Colorado State University. Libraries, 2021) Markovic, Sean, author; Klett, Jim, advisor; Newman, Steven, committee member; Pilon-Smits, Elizabeth, committee member; Prenni, Jessica, committee member; Argueso, Cris, committee member
Moroccan pincushion (Pterocephalus depressus) is a drought tolerant perennial that is being used in landscapes throughout arid areas of the western United States. Commercial producers have had difficulty in producing enough plants to meet demand for moroccan pincushion due to production and propagation stock plant problems. Producers of comparable ornamental perennials have increased their use of gibberellic acid 3 (GA3) in stock plant production. The use of GA3 has increased the yield of vegetative cuttings from perennial stock plants. The plant hormone GA3 is involved in many physiological processes, including plant growth and development. In current literature, few reports are available on the interaction between exogenous GA3 and other plant hormones and their effect on successful propagation of vegetative cuttings. However, the research clearly demonstrated that several different hormone interactions with GA3 could beneficially affect the cutting's rooting physiological process. First, this study describes two experiments researching optimization of stock plant production. Moroccan pincushion stock plants received foliar applications of GA3, benzyladenine, ethephon, or indole-3-butyric acid (IBA) plant growth regulators (PGR). Plant growth regulators were applied singularly and in combination with GA3 to determine efficacy on stock plant production. A propagation study was conducted simultaneously to determine effects of these different PGR treatments on the rooting of moroccan pincushion cuttings. The stock plant study showed GA3 + benzyladenine increased cutting production over other treatments. Fresh weight of moroccan pincushion did not differ among treatments. While dry weight showed no differences in experiment 1, but in experiment 2 differences were observed. The GA3 + IBA treatment had the greatest overall growth. Treatments that included GA3 were all greater in average growth index [(height + width + width)/3] and differed from those without GA3 being applied. The propagation experiments indicated rooting percentages did not differ among treatments. However, growers look for 100% rooting and GA3 + IBA was the only treatment with 100% rooting percentage for both experiments indicating potential benefits. The second part of this paper was to determine the movement and accumulation of GA3 and IBA in treated moroccan pincushion (Pterocephalus depressus). Plants were treated with GA3 alone and in combination with benzyladenine, ethephon, or IBA by either a foliar or drench application method. The amount of GA3 and IBA found in basal and apical sections of moroccan pincushion was analyzed using liquid chromatography/ mass spectrometry (LC/MS). Results shown that drench applications effected the movement of GA3 when GA3 was combined with IBA or benzyladenine. The movement of IBA was affected by drench applications the greatest when GA3 + IBA were applied. Both GA3 and IBA were found in the greatest abundance when plants were treated with GA3 + IBA in apical areas of moroccan pincushion. Nutrients in the cuttings were also analyzed. Only potassium had a significant difference for the amount found when treated with GA3 as a drench application. Other nutrients detailed in this study were not affected by different PGR treatments. This study highlights the beneficial effect of GA3 on production of vegetative cuttings without adverse effects on successful rooting of the cutting.
Open Access
Plant selenium accumulation and the rhizosphere effect
(Colorado State University. Libraries, 2011) Alford, Élan Reine, author; Paschke, Mark W., advisor; Binkley, Dan, committee member; Borch, Thomas, committee member; Pilon-Smits, Elizabeth, committee member; Stromberger, Mary, committee member
To view the abstract, please see the full text of the document.
Open Access
Root-rhizosphere interactions and modifications
(Colorado State University. Libraries, 2016) Lapsansky, Erin Rebecca, author; Vivanco, Jorge M., advisor; Stromberger, Mary, committee member; Pilon-Smits, Elizabeth, committee member; Wallner, Stephen, committee member
The interactions between the plant and rhizosphere are complex, but recent research is elucidating more about a diverse array of relationships. In response to the growing demand for natural or plant produced pesticides and herbicides, a novel method for the identification of bioactive root exudates was developed utilizing the hypothesis that exudate compounds changing in relative abundance over plant development were likely bioactive. Research investigated this hypothesis on Arabidopsis grown in vitro and then in maize grown under greenhouse conditions. Four compounds were identified as bioactive, modifying plant growth, supporting this novel method of bioactive compound identification. In a second study, it was hypothesized that Plant Growth Promoting Rhizobacteria (PGPR) could be used to induce specific changes to Root System Architecture (RSA) which could impart growth benefits in specific environmental conditions. In vitro, three bacterial strains displayed the ability to modify RSA, and in a greenhouse study with nutrient deficiency, one strain was able to impart growth benefit to Arabidospsis. Both bioactive root exudates and PGPR demonstrated the potential to create desired root morphology, suggesting that root systems could be optimized to overcome environmental limitations such as drought or nutrient deficiency. Finally, a review focusing on a novel interpretation of the relationship between plants and the rhizosphere, discusses how the plant primes the rhizosphere to support and protect its offspring.
Open Access
Stock plant management of Lavandula angustifolia 'Wee One' using plant growth regulators and propagation techniques used to create optimal protocols for several Plant Select® species
(Colorado State University. Libraries, 2021) Schriner, Lauryn, author; Klett, James E., advisor; Eakes, Donald J., committee member; Pilon-Smits, Elizabeth, committee member
Lavandula angustifolia 'Wee One' is a drought tolerant dwarf herbaceous perennial being promoted by Plant Select®. The increased demand for this herbaceous perennial has resulted in problems with stock plant management and propagation due to the relatively small vegetative growth. The objective of this study was to determine the effects of plant growth regulators applied as foliar sprays on the vegetative growth of Lavandula angustifolia 'Wee One' propagation stock plants. Five chemical plant growth regulators were applied at the optimal recommended rates : 1) Ethephon (2-Chloroethyl) phosphonic acid [500 mg·L-1 (ppm)] (Verve, Nufarm Americas, Inc., Alsip, IL). 2) Kinetin, Gibberellic Acid, Indole-3-butyric Acid [500 mg·L-1 (ppm)] (Gravity, Winfield Solutions, LLC, St. Paul, MN), 3) N-(phenylmethyl)-IH-purine 6-amine, Gibberellins A4A7 [100 mg·L-1 (ppm)] (Fascination, Valent USA Corp., Fresno, CS), 4) N-(phenylmethyl)-1H-purine-6-amine [400 mg·L-1 (ppm)] (Configure, Fine Agrochemicals Limited, Worcester, U.K.), 5) Gibberellin A3 [100 mg·L-1 (ppm)] (ProGibb T&O, Valent USA Corp., Fresno, CS). Fifteen replications of Lavandula angustifolia 'Wee One' were evaluated once for four months for plant height, width, number of cuttings, and fresh & dry weight of the cuttings. This study was replicated twice, the first experiment was performed from March 2020 to July 2020 and the second experiment was performed from August 2020 to December 2020. Lavandula angustifolia 'Wee One' stock plants that were treated with ProGibb T&O at 100 mg·L-1 (ppm) resulted in larger stock plants with more cuttings produced. A secondary rooting study was conducted at the same time of each experiment. Cuttings were taken at the same time of day and stuck in trays of 26-strip Jiffy® Preforma media and placed under mist with bottom heat at a temperature of 23.9°C. Number of visible roots and rooting percentages were then recorded every week for four weeks. Rooting of Lavandula angustifolia 'Wee One' resulted in no observed differences between plant growth regulator treatments and the control. In conclusion, the use of plant growth regulators resulted in increases of propagation material for Lavender stock plants. Foliar applications of ProGibb T&O at 100 mg·L-1 (ppm) caused an increase in growth of vegetative material and increased the number of cuttings produced from each stock plant with no decreases in the rooting percentage of those cuttings. Epilobium canum subsp. garrettii 'PWWG01S', Osteospermum species, and Pterocephalus depressus are three herbaceous perennials being promoted by Plant Select®. The increased demand for these perennials has resulted in problems with current propagation protocols and production of rooted cuttings. The objective of the propagation techniques study was to determine the optimal combination of rooting hormone, root zone heating temperature, and hormone application methods that would result in higher rooting percentages of cuttings in four weeks. The first experiment focused on two concentrations of Dip N Grow rooting hormone applied to a cutting and placed on two different root zone heating temperatures. Three replications of this experiment occurred from July 2019 to September 2019. The second experiment focused on two rooting hormones (Dip N Grow and Hortus IBA) applied at a single concentration with two different application methods of quick dip (30 seconds) or immersion (3 minutes). Two replications of this experiment occurred from February 2020 to March 2020. After these two experiments, recommendations for propagation protocols can be written. Pterocephalus depressus prefer quick dip application of 30 seconds with either rooting hormone at 500 mg·L-1 (ppm) at a 23.9°C root zone heating temperature. Osteospermum species prefer an immersion application of 3 minutes with Dip N Grow at 500 mg·L-1 (ppm) at a 20°C root zone heating temperature. Epilobium canum subsp. garrettii 'PWWG01S' prefer a quick dip application of 30 seconds with either hormone at 500 mg·L-1 (ppm) with a root zone heating temperature of 20°C. All these recommended propagation techniques resulted in faster rooting and higher rooting percentage when compared to the untreated controls.
Open Access
Synthetic hexaploid wheat contributes favorable alleles for yield and yield components in an advanced backcross winter wheat population
(Colorado State University. Libraries, 2012) Pranger, Anna Leigh, author; Byrne, Pat, advisor; Haley, Scott, committee member; Pilon-Smits, Elizabeth, committee member
To view the abstract, please see the full text of the document.
Open Access
Warm season turfgrasses as potential candidates to phytoremediate arsenic pollutants at Obuasi Goldmine in Ghana
(Colorado State University. Libraries, 2012) Owusu Ansah, Koduah, author; Qian, Yaling, advisor; Koski, Tony, committee member; Pilon-Smits, Elizabeth, committee member
Ghana, originally known as the Gold Coast prior to March 6, 1957, has generally had a very long history of gold mining dating back over 1000 years. Gold is one of the largest contributors to the economy, including cocoa (Gavin, 2002), accounting for about 38% of total merchandise and 95% of total mineral exports as well as about 80% of all mineral revenue. Arsenic enters the environment from a variety of sources associated with gold mining, including waste soil and rocks, tailings, atmospheric emissions from ore roasting, and bacterially enhanced leaching. The combination of opencast mining by multi-national mining companies and heap leaching generates large quantities of waste soil and rock (overburden) and residual water from ore concentrations (tailings) into various water bodies in and around Obuasi. Arsenic constitutes the major trace element problem in the Obuasi area. Extremely high concentrations of this element have been observed in ponds (2250μg/L (USEPA)) and drinking water (1400μg/L). These high levels are far above recommended United States Environmental Protection Agency's (USEPA) drinking water guideline of 10μg/L for Arsenic. At least 10% of rural populations rely on Ghana's borehole wells that have Arsenic concentrations exceeding 10μg/L (USEPA). The basic idea that plants can be used for environmental remediation is very old and cannot be traced to any particular source. However, a series of scientific discoveries combined with an interdisciplinary research approaches have allowed the development of this idea into a promising, cost-effective, and environmentally friendly technology (Pilon-Smits, 2005). This paper reviews the physiological characteristics of five selected native turfgrasses and one exotic grass found in Ghana and their ability to phytoremediate arsenic pollutants at Obuasi mines.