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1
Struckhoff, Garrett Cletus Parkin Gene F. "Plant-assisted bioremediation of perchlorate and the effect of plants on redox conditions and biodiversity in low and high organic carbon soil". [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/441.
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2
Struckhoff, Garrett Cletus. "Plant-assisted bioremediation of perchlorate and the effect of plants on redox conditions and biodiversity in low and high organic carbon soil". Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/441.
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Perchlorate is a known inhibitor of the human thyroid gland. Perchlorate is destroyed by ubiquitous perchlorate-reducing bacteria. The bacteria often lack sufficient electron donor. Research was undertaken to evaluate the relationship between plants and perchlorate-reducing bacteria. To what degree can plant-produced electron donors stimulate perchlorate reduction in low organic carbon (LOC) and high organic carbon (HOC) soil? A complication is that plants have been shown to influence redox conditions which may inhibit perchlorate reduction. The removal of perchlorate in a flow-through reactor was monitored with variables of soil organic carbon, hybrid poplar trees, and bioaugmentation. The biodiversity was monitored using denaturing gradient gel electrophoresis.
Low oxidation-reduction potential (ORP) was shown to indicate the capacity for greater perchlorate removal in soil. However, in planted LOC soil systems, evidence suggests that perchlorate reduction may also be possible at higher bulk redox conditions than previously observed. Increased hydraulic retention time was shown to both lower bulk ORP and increase perchlorate removal.
Radiolabeled perchlorate was used to find that in planted systems as much as 11.7% of the influent perchlorate mass was taken up into the tree and 82% of the perchlorate taken up was accumulated in the leaves. The plant contribution to total perchlorate removal in nonbioaugmented LOC soil was 39%, with the balance of the removal being attributed to microbial reduction. In bioaugmented soil the microbial contribution to perchlorate removal was increased.
Just planting poplar trees decreased the diversity of perchlorate reducers in the soil. However, when LOC soil was both planted and bioaugmented, the diversity of perchlorate reducers was not decreased. In HOC soil, the presence of an indigenous population of microorganisms competed with perchlorate reducers. At the increased ORP observed in planted HOC soil, the non-perchlorate-reducing bacteria appear to outcompete the perchlorate reducers and perchlorate removal is decreased.
Engineering implications of this research are that perchlorate remediation in HOC soil does not benefit from planting hybrid poplar trees but that remediation in LOC soil is stimulated by planting and bioaugmentation.
3
Sakhatska, I. M. "Study of medicinal plants with sedative effect". Thesis, БДМУ, 2021. http://dspace.bsmu.edu.ua:8080/xmlui/handle/123456789/18909.
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4
Chakauya, Ereck. "Effect of manipulating pantothenate biosynthesis in higher plants". Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614866.
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Voss, Joshua. "Forage adaptability trials for forage and seed production in Bolivia : effect of 5 herbicides on 7 native Utah forbs /". Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1639.pdf.
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6
Wang, Ding Xiang. "Interaction between the effects of sodium chloride and high temperature on the vegetative growth of tomato (Lycopersicon esculentum Mill.)". Title page, contents and summary only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phw2456.pdf.
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Sangwan, Veena. "Temperature sensing in plants". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37831.
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It is now well established that cold-triggered calcium influx mediates cold-induced gene expression and development of freezing tolerance (cold acclimation). In this thesis, cold signaling events both upstream and downstream of calcium influx were examined.First, it was shown that the studies on calcium mediation of cold acclimation in alfalfa cell suspension cultures could be applied to intact seedlings of Arabidopsis. Calcium chelators and channel blockers caused a strong reduction in the cold-induced accumulation of kin1 and kin2 transcripts, suggesting that calcium influx was an essential event during cold signaling and that the source of calcium for this influx was largely the calcium-rich cell wall. Evidence suggesting the involvement of calcium-dependent protein kinases (CDPKs) was also obtained.
Second, the nature of events upstream of calcium influx was explored. For this study, transgenic Brassica napus seedlings possessing both the endogenous cold-inducible BN115 gene and the coding part of beta-glucuronidase (GUS) gene placed under the control of the BN115 promoter were used. Thus cold-activation of the BN115 promoter drove the expression of both BN115 at the transcriptional level and the GUS enzyme activity at the translational level. Cold-activation of BN115 was inhibited by chemicals which cause membrane fluidization, cytoskeletal stabilization and inhibition of Ca2+ influx, and mimicked at 25°C by chemicals causing membrane rigidification, cytoskeletal destabilization and Ca2+ influx. Inhibitors of protein and lipid kinases prevented cold-activation of BN115, but inhibition of protein phosphatases activated BN115 at 25°C.
Third, given the increasing importance of mitogen-activated protein kinases (MAPKs) in signal transduction, the nature of molecular mechanisms that lead to cold-activation of a previously reported MAPK, SAMK, was investigated. During this study, the first plant MAPK activated by heat shock was discovered and named HAMK (Heat-shock-activated MAPK). It was shown that cold-activation of SAMK is mediated by cold-induced membrane rigidification, whereas the heat shock-activation of HAMK occurs through heat shock-induced membrane fluidization. Whereas activation of both SAMK and HAMK is blocked by an actin microfilament stabilizer, it is mimicked at 25°C by chemical destabilizers of microtubules or actin microfilaments. All of these events are inhibited by blocking the influx of extracellular Ca 2+. Cold-activation of SAMK and heat-activation of HAMK was prevented by treatment of cells with inhibitors of CDPKs. Thus, cold and heat shock are sensed by structural changes in the plasma membrane, which transduces the signal via cytoskeletal rearrangements to the opening of calcium channels, leading to Ca2+ influx, activation of CDPKs and activation of distinct MAPK cascades.
8
Gencoglu, Cihangir. "Assessment Of The Effect Of Hydroelectric Power Plants'". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612165/index.pdf.
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The Turkish TSO (TEIAS) has been leading a project that aims the synchronous interconnected operation of the Turkish Power System and the ENTSO-E CESA (former UCTE) System. For this purpose, this study concentrates on the specific problems related to the electromechanical systems of large size hydroelectric power plants regarding low frequency inter area oscillations, which are prone to occur once the interconnected operation is established. The expected frequency of inter area oscillations after interconnected operation is close to 0.15 Hz, which is in the frequency range of the speed governing structures of turbines, as explained in the first two sections of the thesis. In the third section, the nonlinear turbine governor model used throughout the study is explained. In the following part, the governor parameter tuning study with regard to the defined performance objectives is explained. Afterwards, the effect of the retuned governor settings of the sample hydroelectric power plants on a simple multi machine power system is shown. Following that, the system wide effect of removing the sources of negative damping, which are strongly dependent on the governor settings of the major hydroelectric power plants of the Turkish Power System, is shown. In the final part, conclusions are made on the operation of the hydroelectric power plants regarding the frequency stability of the system after synchronous interconnected operation of the Turkish Power System and the ENTSO-E CESA System.
9
Lau, Ka Keung. "Effect of Oâ†3 fumigation on nitrate reduction in plants". Thesis, Lancaster University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337586.
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LoÌpez-Chuken, Ulriko J. "The effect of chloro-complexation on cadmium uptake by plants". Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430615.
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11
McKee, J. "The effect of temperature on sexual reproduction in flowering plants". Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360337.
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Mjwara, Jabulani Michael. "The interactive effects of light, temperature and CO₂/O₂ ratios in photosynthesis of Coix lachryma-jobi L". Thesis, Rhodes University, 1992. http://hdl.handle.net/10962/d1003785.
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A portable infra red gas analyzer was used to investigate the interactive effects of light, temperature, and CO,jO, ratios under controlled environmental conditions in an attempt to model gas exchange characteristics of Coix Iachryma-jobi L. Plotting light response curves as a function of temperature (20, 25 30 and 35°C) revealed no sign of light saturation even at a photosynthetic photon flux density (PPFD) close to 2000 !Lmol m-' sol. High net assimilation rates (A) of approximately 24 !Lmol CO, m"s'! were realized at 30-35°C. Assimilation (A) versus internal CO, partial pressure (C,) curves showed a steep rise with increase in C, but saturated at approximately 150 (JLII-!) and all the results, either in the absence or presence of 0" showed a similar response under all temperature regimes. C. Iachryma-jobi exhibited low CO, compensation points cr ) between 0 and 10 JLlI-! under similar experimental temperatures and either at 0 or 21%0,. The slopes of double reciprocal plots of llA versus llCi, were nearly identical and crossed the yintercept at almost identical points under all 0, concentrations. These data indicate first; that there was no apparent 0, inhibition and second; indicated that the apparent inhIbitor constant (K,) for 0, at the site of carboxylation did not change with increase in [OJ from 0 to 21% oxygen. These observations were further confirmed by results obtained from the analysis of apparent carboxylation efficiency (CE, as defined as the slope of response of A to increasing CO,), as no inhibition of A with increase of [OJ occurred. These characteristics were consistent with typical features of C,photosynthesis. The absence of 0, inhibition and low r values indicated that an efficient CO, concentrating mechanism which eliminates photorespiration exists in C. Iachryma-jobi. At the light microscope level, leaf anatomy exhibited typical C, structure viz. bundle sheath with large chloroplasts and this sheath is further surrounded by a radiate Kranz mesophyU cells. Furthermore the anatomical features suggested that C. wchryma-jobi was an NADP-ME species. Stomatal conductance (g,) to assimilation (g,/A) indicated an increase in A with decrease in g" an essential feature of improving water use efficiency (WUE), but one which drastically reduces CO, diffusion rate. The physical lintitation (stomatal lintitation, t) to CO, diffusion under various [0,] and temperatures, but constant PPFD, did not exhibit statistically significant change in t values at either 0 or 21% a, within each temperature regime, however there was a marked decrease in t as the plant approached its optimum photosynthetic temperature.
13
Anderson, Annette. "The effects of acetolactate synthase (ALS) inhibiting herbicides on the growth, yield, nodulation and nitrogen fixation of selected legumes". Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09pha545.pdf.
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Bibliography: leaves 251-268. The main aim of this thesis is to determine the effects of sulfonylurea residues and in-crop usage of selected ALS-inhibiting herbicides on the growth, yield, nodulation and nitrogen fixation of legumes under alkaline conditions. Reviews literature concerning ALS-inhibiting herbicides, nitrogen fixation and the effects of herbicides on legumes, rhizobia, nodulation and nitrogen fixation; Glasshouse trial investigating the effects of flumetsulam on biomass and nodulation of chickpea; Field trail investigating the effects of sulfonylurea residues and 'in crop' usage of flumetsulam on medic shoot biomass and seed yield and the effects of chlorsulfuron residues and 'in crop' usage of flumetsulam and imazethapyr on chickpea shoot biomass, grain yield and nitrogen fixation; develops methodologies for experiments investigating the effects of ALS-inhibiting herbicides on nodulation of chickpea.
14
Greyvenstein, Fritz Siegruhn. "Performance prediction for multi-effect distillation (MED) plants / by F.S. Greyvenstein". Thesis, North-West University, 2007. http://hdl.handle.net/10394/855.
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Many countries worldwide experience water shortages on a daily basis and this water
crisis is expected to increase even more in the near future due to limited fresh water resources. Alternative sources of fresh water such as desalinated seawater are becoming an attractive option for many developing countries. Although various desalination technologies exist today, interest in multi-effect distillation (MED) is growing rapidly worldwide. Today various energy power sources are utilized in MED plants, but the use of nuclear power as a clean and effective heat source for the MED process seems to be gaining interest. Implementation of HTGR technology, such as the Pebble Bed Modular Reactor being developed in South Africa is ideal for MED desalination purposes. In these types of reactors high temperature water is available as waste heat as opposed to high temperature steam from conventional steam power plants. Currently conventional MED plants utilize steam as the process heat source, to drive the MED process.
In this study a system simulation model was developed in the computer language C++. It evaluates different MED process flow configurations in order to identify an optimum MED plant configuration for both water and steam as process heat source. Simulation results indicate that a steam-heat-source (SHS) MED plant produces approximately 25-30% more product water than a water-heat-source (WHS) MED plant while utilizing less plant stages. Plant layout and economics are impacted by the available process heat source. Results also indicate that a parallel feed configuration (PFC), which incorporates preheating of feed water, seems to be the optimum process flow configuration type for both the SHS and WHS type plants. Product water costs for optimized SHS and WHS MED plants were also compared. Various system parameters influence plant performance, but the serie effect temperature difference seems to be the most influential parameter in terms of water production. Preheating of feed water increases production levels up to 30%. Results from the C++ model have been compared to results calculated with MEE-TVC, a desalination system design program and were generally in good agreement.Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2008.
15
Torp, Mikaela. "The effect of snow on plants and their interactions with herbivores". Doctoral thesis, Umeå : Department of Ecology and Environmental Science, Umeå University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-30444.
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Ingarfield, Patricia Jean. "Effect of water stress and arbuscular mycorrhiza on the plant growth and antioxidant potential of Pelargonium reniforme Curtis and Pelargonium sidoides DC". Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2794.
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Thesis (MTech (Horticulture))--Cape Peninsula University of Technology, 2018.Pelargoniums have been studied extensively for their medicinal properties. P. reniforme and P. sidoides in particular are proven to possess antimicrobial, antifungal and antibiotic abilities due to their high antioxidant potential from compounds isolated from their tuberous roots. These plants have now been added to the medicine trade market and this is now causing concern for conservationists and they are generally harvested from the wild populations. This study evaluated the effect of water stress alone and in conjunction with arbuscular mycorrhiza on two species of Pelargoniums grown in a soilless medium. The experiment consisted of five different watering regimes which were applied to one hundred plants of each species without inoculation with arbuscular mycorrhiza and to one hundred plants of each species in conjunction with inoculation with AM. All the plants in the experiment were fed with a half-strength, standard Hoagland nutrient solution at varying rates viz. once daily to pot capacity, every three days to pot capacity, every six days to pot capacity, every twelve days to pot capacity and every twenty-four days to pot capacity. The objectives of the study were to measure the nutrient uptake, SPAD-502 levels (chlorophyll production) and metabolite (phenolics) formation of both species, grown under various rates of irrigation and water stress, as well with or without the addition of arbuscular mycorrhiza at planting out. Each treatment consisted of 10 replicates. SPAD-502 levels were measured weekly using a hand held SPAD-502 meter. Determination of nutrient uptake of macronutrients N, K, P, Ca, Mg and Na and micronutrients Cu, Zn, Mn, Al and B were measured from dry plant material at the end of the experiment by Bemlab, 16 Van Der Berg Crescent, Gants Centre, Strand. Plant growth in terms of wet and dry shoot and root weight were measured after harvest. Determination of concentrations of secondary metabolites (phenolic compounds) were assayed and measured spectrophotometrically at the end of the experiment. The highest significant reading of wet shoot weight for P. reniforme was taken in treatments 1 and 2 with and without mycorrhiza i.e. WF1, WF1M, WF2 and WF2M, with the highest mean found in WF1 with no mycorrhiza. This indicates that under high irrigation AM plays no part in plant growth, possibly due to leaching. More research is necessary in this regard. With regard to wet root weight, this was found to be not significant in any of the treatments, other than the longest roots being found in WF4. Measurements for dry root weight showed that WF1,2,3 and 5 were the most significant at P≤ 0.001 significance, with the highest weight found at treatment being WF3 and WF3M. The highest mean of shoot length of the plants was measured in treatment WF2 at moderate watering, but no statistical difference was found with water application and mycorrhiza addition. Nutrient uptake was increased in P. sidoides in all the different watering levels in the experiment except in the uptake of Mg. AM inoculation showed an increase in the uptake of Ca, while absorption of N occurred at higher water availability. K uptake was enhanced by the addition of AM in high water availability and K utilisation decreased as water stress increased. Medium to low watering resulted in higher leaf content in P. sidoides while the interaction between water availability and AM inoculation increased chlorophyll production towards the end of the experiment.
17
Lumbuenamo, Sinsi Dianza 1954, e Sinsi Dianza 1954 Lumbuenamo. "Litter cover effect on soil spectral response". Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276620.
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In order to assess the influence of litter cover on soil background spectral response, trays of dry Lehmann Lovegrass (Eragrostis lehmanniana) were used at three different densities (635, 1015, 2815 Kg/ha) over three different soil backgrounds (Whitehouse sandy clay loam, Superstition sand, and Cloversprings loam). After analysis, spectral measurements made with a Barnes Multi-Modular Radiometer revealed that, soil-litter mixtures exhibit an oil like spectral behavior in the (0.45-2.30 m) waveband range. Mulched soils could not be discriminated from bare soils solely on the basis of the spectral response. However, mulched and bare soil spectral responses differed in amplitude depending on the difference in brightness between the bare soil and the litter cover. In addition, the results showed that while an increase of litter cover density on the soil surface decreased RVI, NDVI and PVI predicted greenness, it increased the GVI based greenness for all soils except the Superstition sand where the GVI showed a reversed trend. The PVI increased at low and intermediate litter densities and decreased at higher ones for the Superstition sand.
18
Ayub, Najma. "The effect of VAM inoculation on interplant ¹⁵N transfer". Thesis, University of Aberdeen, 1991. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU546184.
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This thesis reports a study carried out to investigate the involvement of VA mycorrhizas in interplant 15N transfer in a model pasture system and in a model agroforestry system. Two pot experiments were designed to investigate the effect of VAM inoculation on 15N transfer from clover to rye grass in sterile (in the first experiment the sterilisation was by autoclaving and in the second, by gamma-irradiation) and fresh soil. A third pot experiment was designed to investigate the effect of VAM inoculation on 15N transfer from grass and clover to wild cherry seedlings in fresh soil. For these pot experiments donor plant seedlings were labelled with 15N by growing in Hoaglands solution containing K 15NO3 (5 atom % 15N). To study 15 N transfer and its possible mechanisms, plants and soil samples were analysed for 15N, total N (14N + 15N) and P concentrations. Rates of soil nitrogen mineralisation and nitrification, as well as 15N enrichment of available N were also determined to investigate N transfer through soil. There was transfer of 15N from donor to receiver in the simulated pasture system as well as in simulated agroforestry system. The transfer of 15N was increased by VAM inoculation. The transfer of 15N was small in relation to plant nutrition and was not associated with an increase in total N in the receiver plants although P concentrations were generally increased. There was no increase in the soil N fluxes of mineralisation and nitrification associated with enhanced 15N transfer from donor to receiver in the VAM inoculated system. In addition, there was often no increase in the 15N concentration in the soil available N pool of VAM inoculated systems. There was no evidence, therefore, of increased transfer of 15N through the soil in VAM inoculated systems with enhanced 15N interplant transfer, suggesting the likely involvement of VAM fungal hyphae. There was no marked effect on plant growth due to VAM inoculation. The growth of cherry, however, was reduced when grown with grass and this may have been due to N competition between the root systems. The growth of cherry seedlings was reduced to a lesser extent when grown with clover compared to when grown with grass. The findings of this study suggest that VA mycorrhizal hyphae play a part in interplant transfer of nitrogen. Although the study did not demonstrate high rates of 15N transfer in VAM inoculated system, circumstances are discussed where VAM interplant transfer of nutrients may become significant at the single plant, community and ecosystem level. The benefits to man of VAM mediated N transfer may be best realised in land use systems such as pastures having legumes and non-legumes, in mixed cropping of legumes and non-legumes and in an agroforestry system with a legume component, particularly when the soil is deficient in nutrients such as nitrogen and phosphorus.
19
Brownell, Peter Ferguson. "Sodium as an essential element for C4 plants /". Title page, contents and summary only, 1993. http://web4.library.adelaide.edu.au/theses/09SD/09sdb884.pdf.
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Kalifa, Ali. "Salt stress, and phosphorus absorption by potato plants cv. 'Russet Burbank'". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29727.pdf.
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Adhikari, Sajag. "Solvent Effects and Bioconcentration Patterns of Antimicrobial Compounds in Wetland Plants". Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc67953/.
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This study looked at effects of organic solvents dimethylsulfoxide, dimethylformamide and acetone at 0.01%, 0.05% and 0.1% concentration on germination and seedling development wetland plants. Even at 0.01% level, all solvents affected some aspect of seed germination or seedling growth. Acetone at 0.01% was least toxic. Root morphological characteristics were most sensitive compared to shoot morphological characteristics. This study also looked at bioconcentration patterns of antimicrobial compounds triclosan, triclocarban and methyl-triclosan in wetland plants exposed to Denton Municipal Waste Water Treatment Plant effluent. Bioconcentration patterns of antimicrobial compounds varied among species within groups as well as within organs of species. The highest triclocarban, triclosan and methyltriclosan concentration were in shoot of N. guadalupensis, root of N. lutea and in shoots of P. nodous respectively.
22
Ayeni, Olutoyosi Olaide. "Growth responses within the Genus Cyperus exposed to aluminium and iron in hydroponics". Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2430.
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Thesis (DTech (Environmental Health))--Cape Peninsula University of Technology, 2016.Generally, aluminium (Al) is required as a micronutrient by plants. The metabolism of Al within the plant can exert a number of effects within the plant. These include: interfering with cell division in both root tips and lateral roots, increasing cell wall rigidity, maintaining the correct cellular redox state, as well as the various other physiological and growth responses. Al is one of the most abundant elements in the earth’s crust and becomes toxic in many plants when the concentration is greater than 2-3 ppm, where the soil has a pH<5.5. Iron (Fe) is an equally important element, and the toxicity of this metal possesses constraints primarily on wetland plants growing in acidic soils that have high reducible iron content. The impact of metal toxicity (Al and Fe) requires an understanding of many aspects related to Al and Fe uptake, transport and distribution by plants in wetland ecosystems. In this study, three species of Cyperus viz. Cyperus alternifolius, Cyperus prolifer and Cyperus textilis were used to carry out phytotoxicity tests to monitor xenobiotic substances.
23
Eakes, Donald Joseph. "Moisture stress conditioning, potassium nutrition, and tolerance of Salvia splendens 'Bonfire' to moisture stress". Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54350.
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The objective of this study was to determine the leaf water relations, gas exchange, and growth of the bedding plant salvia Salvia splendens 'Bonfire‘ as influenced by moisture stress conditioning (MSC - exposing plants to 4 sublethal dry-down cycles) and potassium (K) nutrition. Plants were fertilized with one of six K rates: 25, 75, 150, 300, 450, and 600 ppm as KCl in experiment one. Seven weeks after seeding plants were subjected to MSC. MSC and increasing K rate resulted in osmotic adjustment and increased cellular turgor potentials. Foliar K content increased as osmotic potentials decreased due to treatment. Although there was no interaction, MSC and high K rates both reduced transpiration (E), leaf conductance (g₁), and daily gravimetric water loss during well watered conditions. Greatest shoot dry weight occurred for plants grown with 300 ppm K and no-MSC.
Gas exchange of salvia as influenced by MSC during the onset of moisture stress was determined in experiment two. On day one following final irrigation, MSC plants had lower mid-day E, g₁, hourly gravimetric water loss per unit leaf area, and net photosynthesis (Pn) compared to controls, despite no differences in leaf water potential (ψ₁). Percentage of stomatal inhibition of Pn (SI) was greater for MSC plants than controls with no differences in mesophyllic resistance to CO₂ (rm). On day two, MSC plants had greater Pn, E, g₁, and hourly gravimetric water loss per unit leaf area, while SI and rm were lower than controls. MSC plants maintained positive Pn rates and turgor to lower ψ₁ than control plants. Water use efficiency (WUE) estimates for MSC plants were greater than for controls.
Salvia plants were fertilized with 75, 300, or 600 ppm K to determine the influence of K rate on gas exchange during the onset of moisture stress in a third experiment. On day one following final irrigation, plants grown with K rates of 300 and 600 ppm had lower E, g₁, hourly gravimetric water loss per unit leaf area, and Pn compared to 75 ppm K plants. On day two, 600 ppm K plants had greater Pn, E, and g₁ as the experiment was terminated compared to plants grown with 75 ppm K, although ψ₁ was similar. Potassium rate had little affect on WUE.Ph. D.
24
Voigt, Astrid. "Bioavailability of trace metals to plants". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19561.
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Soil quality guidelines are currently based on total trace metal loads. There is a need to define indices of bioavailability to allow reasonable predictions for plant metal uptake and toxicity in soils. Trace metal toxicities to plants often correlate best with free metal ion activities. The first objective was to develop a plant bioassay that is sensitive to trace metals at concentrations realistic for soils. The root elongation of lettuce Lactuca sativa 'Buttercrunch' was used as toxicological endpoint. This endpoint was sensitive and reproducible to environmentally relevant concentrations of Cd, Cu, Ni, Pb and Zn. The second objective was to test whether free metal ion activities are constant predictors of metal toxicities in synthetic solutions and in soil extracts that differ in their concentrations of cations and ligands. The root elongation assay was used to test this hypothesis. In synthetic solutions, the rhizotoxicity of Cd, Cu, Ni, Pb and Zn decreased with increasing Ca and H concentrations. This could not be explained with the effect of higher cationic concentrations on root growth or on solution speciation. It was concluded that Ca and H inhibited the rhizotoxicity of all metals tested. The rhizotoxicity of Cu and Cd was further examined in soil extracts. Both metals became less rhizotoxic at higher H and dissolved organic matter concentrations. The rhizotoxicity endpoints from the experiments in synthetic solution were used to develop parameters for a Biotic Ligand Model (BLM) for Cd, Cu, Ni, Pb and Zn. The BLM accounts for solution speciation and interprets cationic inhibition of rhizotoxicity as competition of metals with Ca and H for potential sites of rhizotoxicity. The BLM predicted metal rhizotoxicity better than the free metal ion activity in synthetic solutions and in soil extracts. Different models were tested against literature rhizotoxicity data for metals at different Ca and H concentrations. Predictions for metal rhizotoxicity given by BLM, Gouy-Chapman-Stern model and Freundlich equation model were compared with predictions based on free metal ion activities in solution. The BLM predicted rhizotoxicity most accurately. The BLM seems promising for predictions of metal toxicity and metal bioavailability in soils to support site-specific environmental risk assessments.
25
Choudhury, Feroza Kaneez. "Rapid Metabolic Response of Plants Exposed to Light Stress". Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157543/.
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Environmental stress conditions can drastically affect plant growth and productivity. In contrast to soil moisture or salinity that can gradually change over a period of days or weeks, changes in light intensity or temperature can occur very rapidly, sometimes over the course of minutes or seconds. So, in our study we have taken an metabolomics approach to identify the rapid response of plants to light stress. In the first part we have focused on the ultrafast (0-90 sec) metabolic response of local tissues to light stress and in the second part we analyzed the metabolic response associated with rapid systemic signaling (0-12 min). Analysis of the rapid response of Arabidopsis to light stress has revealed 111 metabolites that significantly alter in their level during the first 90 sec of light stress exposure. We further show that the levels of free and total glutathione accumulate rapidly during light stress in Arabidopsis and that the accumulation of total glutathione during light stress is dependent on an increase in nitric oxide (NO) levels. We further suggest that the increase in precursors for glutathione biosynthesis could be linked to alterations in photorespiration, and that phosphoenolpyruvate could represent a major energy and carbon source for rapid metabolic responses. Taken together, our analysis could be used as an initial road map for the identification of different pathways that could be used to augment the rapid response of plants to abiotic stress. In addition, it highlights the important role of glutathione in initial stage of light stress response.
Light-induced rapid systemic signaling and systemic acquired acclimation (SAA) are thought to play an important role in the response of plants to different abiotic stresses. Although molecular and metabolic responses to light stress have been extensively studied in local leaves, and to a lesser degree in systemic leaves, very little is known about the metabolic responses that occur in the different tissues that connect the local to the systemic leaves. These could be important in defining the specificity of the systemic response as well as in supporting the propagation of different systemic signals, such as the reactive oxygen species (ROS) wave. Here we report that local application of light stress to one rosette leaf resulted in a metabolic response that encompassed local, systemic and transport tissues (tissues that connect the local and systemic tissues), demonstrating a high degree of physical and metabolic continuity between different tissues throughout the plant. We further show that the response of many of the systemically altered metabolites could be associated with the function of the ROS wave, and that the level of eight different metabolites is altered in a similar way in all tissues tested (local, systemic, and transport tissues). These compounds could define a core metabolic signature for light stress that propagates from the local to the systemic leaves. Taken together, our findings suggest that metabolic changes occurring in cells that connect the local and systemic tissues could play an important role in mediating rapid systemic signaling and systemic acquired acclimation to light stress.
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Attumi, Al-Arbe. "Effect of salt stress on phosphorus and sodium absorptions by soybean plants". Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20242.
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The radiotracer methodology was combined with the Hoagland solution culture of growing soybean in a greenhouse to investigate the absorptions of phosphorus (P), calcium (Ca), and sodium (Na) as a function of salinity. Salt stress was varied by using zero to 120 mM NaCl. The research was initiated because of a need to increase soybean production in the saline soils of the semi-arid regions of the world. Although P absorption increased with time at each concentration of NaCl, increasing its concentrations ([NaCl]) to 120 mM reduced P uptake considerably. The addition of inorganic P (Pi) to the salt medium improved P absorption significantly (P < 0.0001) in stem, petiole, and roots. Polynomial regressions showed the relationship between 22Na activity and [NaCl] for leaves and petiole to be cubic (R2 = 1) while in the stem a quadratic relationship prevailed. A maximum of P and Na absorption was observed at 40 mM NaCl. The relationship between 32P activity and increasing [NaCl] was linear for the roots (a positive slope) and the stem (a negative slope). 45Ca and 32P dual labelling part of the experiments failed to produce results because an unexpectedly high degree of tissue quenching which prevented from obtaining the minimum counting requirements for separation. Shoot fresh and dry weights decreased linearly with increasing [NaCl] as did the root fresh and dry weights. Leaf chlorophyll content during the last week of the final harvest showed a linear relationship with time. Chlorophyll increased with time linearly when the growth medium contained zero and 40 mM NaCl; whereas a negative slope was obtained for 80 and 120 mM NaCl. It seems that P fertilization of the soil could ameliorate the salt effect. 22 Na uptake results indicated that there is a mechanism for exclusion of Na from soybean plant parts.
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Saif, Salman Mohammed 1958. "EFFECT OF SALINITY ON THE TOMATO PLANTS GROWN IN A HYDROPONIC SYSTEM". Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/277070.
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Barron-Gafford, Greg A., Rebecca L. Minor, Nathan A. Allen, Alex D. Cronin, Adria E. Brooks e Mitchell A. Pavao-Zuckerman. "The Photovoltaic Heat Island Effect: Larger solar power plants increase local temperatures". NATURE PUBLISHING GROUP, 2016. http://hdl.handle.net/10150/621943.
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While photovoltaic (PV) renewable energy production has surged, concerns remain about whether or not PV power plants induce a "heat island" (PVHI) effect, much like the increase in ambient temperatures relative to wildlands generates an Urban Heat Island effect in cities. Transitions to PV plants alter the way that incoming energy is reflected back to the atmosphere or absorbed, stored, and reradiated because PV plants change the albedo, vegetation, and structure of the terrain. Prior work on the PVHI has been mostly theoretical or based upon simulated models. Furthermore, past empirical work has been limited in scope to a single biome. Because there are still large uncertainties surrounding the potential for a PHVI effect, we examined the PVHI empirically with experiments that spanned three biomes. We found temperatures over a PV plant were regularly 3-4 degrees C warmer than wildlands at night, which is in direct contrast to other studies based on models that suggested that PV systems should decrease ambient temperatures. Deducing the underlying cause and scale of the PVHI effect and identifying mitigation strategies are key in supporting decision-making regarding PV development, particularly in semiarid landscapes, which are among the most likely for large-scale PV installations.
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Rahman, Yosra Ahmed Soltan Abd El. "Effect of tanniniferous plants and essential oils on methane emission in ruminants". Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/64/64134/tde-26092012-134451/.
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Tannins and essential oils are secondary metabolites that may be used as natural modifiers of rumen fermentation to reduce the ruminants\' methane (CH4) emission. To study the application of tannin-rich plants from Egypt and Brazil, as well as essential oils that are available in international trade, three studies were conducted at Animal Nutrition Laboratory of Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, at Piracicaba, Brazil. The first study was aimed to assess the potential of tanniniferous plants prosopis (Prosopis juliflora), acacia (Acasia saligna), atriplex (Atriplex halimus) and leucena (Leucaena leucocephala) in in vitro gas production assay, evaluating the methanogenic activity, ruminal fermentation, degradability and post ruminal protein digestibility compared with Tífton hay (Cynodon spp.) as non tannin feed. The ranking of the plants according to their potential to reduce CH4 based on organic matter truly degraded (OMTD) was acacia> leucena> atriplex> prosopis. Prosopis and leucena presented greater (P=0.002) propionate (C3) production with corresponding decrease (P=0.004) in the acetate:propionate ratio (C2/C3). Acacia and leucena showed lower (P=0.0002) NH3-N concentration associated with the decline in protein ruminal degradability. However, leucena showed greater (P<0.001) intestinal protein digestibility than acacia. The objective of the second study was to evaluate in vitro the potential of constituents of essential oils carvacrol (CAR) and eugenol (EUG) at doses of 5, 10 and 20 (CAR) and 10, 20 and 30 (EUG) \'mü\'l/75ml of culture fluid, as a natural alternative to rumen microbial fermentation modifiers compared with monensin (MON) (3 \'mü\'M/75ml of culture fluid) as a positive control. CAR10 and EUG20 showed similarity (P>0.05) in reduction of CH4 emission and OMTD compared with MON, but it had different (P<0.05) short chain fatty acids (SCFA) profile. Monensin increased C3 concentration and decreased C2/C3 ratio, but CAR10 and EUG20 increased (P<0.0001) concentrations of butyrate without effect on the total SCFA. Leucena was selected in the third study to evaluate in vivo the tannins biological activity in total apparent digestibility, nitrogen balance, rumen fermentation and CH4 emission. Six adult rumen cannulated Santa Inês sheep (70±2.5 kg) were individually divided into three experimental diets in a double Latin square design (3 treatments, 3 periods, 6 animals). In the control diet (CNTRL), animals received a basal diet containing Tifton hay (70%), soybean meal (21%) and ground maize (9%). The second diet contained leucena (LEUC), (123 and 8.8 g/kg DM of total tannins and condensed tannins respectively) replacing 50% of Tífton hay. The third diet (LPEG), polyethylene glycol was supplemented at rate of 20g/day/animal. Leucaena-containing diets increased intake of crude protein (P=0.008) and lignin (P<0.001) compared with CNTRL, while there were no significant differences among all diets for the nutrients apparent digestibility except for acid detergent fiber (ADF) was reduced (P=0.0009) by LEUC. Leucaena-containing diet reduced (P<0.001) rumen ammonia concentration and urinary excretion of nitrogen (P=0.0065). Leucena-containing diets decreased (P<0.001) CH4 emission as well as reduced (P<0.001) C2/C3 ratio compared to CNTRL. These studies highlight the potential of tanniniferous plants and the essential oils active components to modulate the rumen fermentation and to reduce CH4 emission in ruminantsTaninos e óleos essenciais são metabólitos secundários que podem ser utilizados como modificadores naturais da fermentação ruminal para reduzir a emissão de metano (CH4) de ruminantes. Para estudar a aplicação de plantas ricas em taninos oriundas do Egito e do Brasil, bem como óelos essencias disponíveis no comércio internacional, três estudos foram conduzidos no Laboratório de Nutrição Animal do Centro de Energia Nuclear na Agricultura da Universidade de São Paulo, Piracicaba. O primeiro estudo teve como objetivo investigar o potencial das plantas taniníferas prosopis (Prosopis juliflora), acácia (Acasia saligna), atriplex (Atriplex halimus) e leucena (Leucaena leucocephala) em ensaio in vitro de produção de gás, avaliando o potencial metanogênico, a degradabilidade ruminal da proteína e a digestibilidade da proteína pós-ruminal, em comparação com feno de Tífton (Cynodon spp.) como alimento sem tanino. O ranking das plantas de acordo com seu potencial de redução de CH4 com base na matéria orgânica verdadeiramente degradada (MODV) foi acácia> leucena> atríplex> prosopis. Prosopis e leucena apresentaram maior (P=0,002) produção de propionato (C3) com diminuição (P=0,004) correspondente na relação acetato:propionato (C2/C3). Acácia e leucena apresentaram menor (P=0,0002) concentração de NH3-N associada com a diminuição na degradabilidade ruminal da proteína. No entanto, a leucena mostrou maior (P<0,0001) digestibilidade da proteína intestinal que a acácia. O objetivo do segundo estudo foi avaliar in vitro o potencial dos óleos essenciais carvacrol (CAR) e eugenol (EUG), nas doses 5, 10 e 20 (CAR) e 10, 20 e 30 (EUG) \'mü\'l/75ml de fluido de cultura, como alternativa de modificadores naturais da fermentação ruminal em comparação com a Monensina (MON) (3 \'mü\'M/75ml de fluido de cultura) como controle positivo. CAR10 e EUG20 apresentaram similaridade na CH4 e MODV comparado com MON, no entanto foram diferentes (P<0.05) no perfil de AGV, onde MON aumentou a concentração de C3 e diminuiu C2/C3, mas ambos CAR10 e EUG20 aumentaram (P<0,0001) as concentrações de butirato. Leucena foi selecionada no terceiro estudo para avaliação in vivo da atividade biológica de taninos na digestibilidade aparente, balanço de nitrogênio, fermentação ruminal e emissão de CH4. Seis ovinos Santa Inês adultos, canulados no rúmen (70±2,5kg) foram individualmente divididos em três dietas experimentais em delineamento quadrado latino duplo (3tratamentos, 3períodos, 6animais). A dieta controle (CNTRL), contendo feno de Tífton (70%), farelo de soja (21%) e milho (9%). A dieta (LEUC), contendo leucena (123 e 8,8g/kg MS taninos totais e taninos condensados, respectivamente), consistiu na dieta controle, tendo 50% do feno de Tífton substituído pela leucena. A dieta LPEG constituiu da dieta LEUC mais a adição de 20g/dia/animal de polietileno glicol (PEG). Dietas contendo leucena aumentaram (P=0,008) a ingestão de proteína bruta, nitrogênio (P=0,005) e lignina (P<0,001) em comparação com CNTRL, enquanto não houve diferenças significativas para as digestibilidades aparentes das nutrientes mas a dieta LEUC diminuiu (P=0,0009) a digestibilidade da fibra em detergente ácido, amônia ruminal (P<0,0001) e excreção urinária de nitrogênio (P=0,0065). Dietas contendo leucena diminuíram (P<0,0001) CH4 bem como diminuíram (P<0,0001) C2/C3 em comparação com CNTRL. Estes estudos destacam o potencial das plantas taniníferas e os óleos essenciais para modular a fermentação ruminal e reduzirem a emissão de CH4
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De, Canha Marco Nuno. "Antimicrobial and anti-inflammatory effect of southern African plants against Propionibacterium acnes". Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/79786.
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Twenty southern African plants were selected based on traditional use. The ethanol extracts were tested for their antimicrobial activity against P. acnes (ATCC 11827) [Propionibacterium acnes (Gilchrist) Douglas and Gunter deposited as Corynebacterium acnes (Gilchrist) Eberson]. The 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of the extracts were also determined.
Cytotoxicity on human macrophage cells (U937) was performed using the 2,3-Bis-(2-Methoxy-4-Nitro-5-Sulfophenyl)-2H-Tetrazolium-5-Carboxanilide (XTT) reduction assay. The cytotoxicity was performed to ensure that the extracts are not toxic to human macrophage cells (U937) and to obtain a non-lethal range of concentrations to be tested in the anti-inflammatory assay. The anti-inflammatory potential was tested using IL-8 as a marker cytokine. This is a pro-inflammatory cytokine secreted when cells are stimulated with heat-killed P. acnes cultures.
During the investigation of the antimicrobial activity, four plant extracts were found to have significant inhibitory activity against P. acnes. Helichrysum odoratissimum showed the best activity with a minimum inhibitory concentration (MIC) at 7.81μg/ml. Clausena anisata, Rapanea melanophloeos and Helichrysum kraussii were also active with MICs at 31.25μg/ml, 15.63μg/ml and 125μg/ml, respectively. All MICs were selected based on PrestoBlue as the growth indicator. Helichrysum odoratissimum showed also showed the best antioxidant activity with an IC50 of 3.86 ± 0.24μg/ml. It was also reported to have the best selectivity index (SI) of 2.76 on U937 cells. Clausena anisata exhibited good antimicrobial activity and low toxicity on U937 cells with an IC50 at 74.46μg/ml and an SI of 2.38.
During the investigation of the synergistic activity of the extracts, the combination of 3.13μg/ml of Helichrysum odoratissimum and Helichrysum kraussii at 0.78μg/ml showed better antimicrobial activity of either of the plant extracts acting alone against P. acnes with a fractional inhibitory index (ΣFIC) of 0.42.
Clausena anisata was selected as the extract for the Interleukin-8 (IL-8) inhibition assay as it was shown to be traditionally used for treatment of many inflammatory disorders or symptoms. The inhibition of IL-8 by C. anisata in vitro when plant extract was added to stimulated U937 cells was low but there was some inhibition. The IL-8 protein concentration produced by U937 cells treated with 100μg/ml of heat-killed P. acnes was 840.52pg/ml. Low levels of IL-8 inhibition were observed when cells stimulated with P. acnes were treated with non-lethal concentrations of C. anisata extract. Treatment with 50μg/ml, 25μg/ml, 12.5μg/ml and 6.25μg/ml showed a decrease in IL-8 to 322.48 ± 0.07pg/ml, 365.98 ± 0.24pg/ml, 383.62 ± 0.08pg/ml and 409.52 ± 0.13pg/ml, respectively. The untreated cell control however, seemed to show spontaneous production of IL-8 with quantified as 488.76 ± 0.06pg/ml, making it difficult to analyse effects of other cell stimulants. This spontaneous release was also inhibited with the addition of C. anisata extract at 50μg/ml, 25μg/ml, 12.5μg/ml and 6.25μg/ml which showed IL-8 levels at 299.24 ± 0.13pg/ml, 357.82 ± 0.07pg/ml, 387.14 ± 0.12pg/ml and 388.74 ± 0.19pg/ml, respectively
The use of many polyherbal formulations is becoming popular practice. Due to the variety of symptoms observed with acne vulgaris it would be beneficial to investigate mixtures of plants showing good antimicrobial, antioxidant, anti-inflammatory and anti-pathogenic activity as potential treatments for acne vulgaris.
This is the first report of the synergistic activity of Helichrysum odoratissimum and Helichrysum kraussii crude ethanol extracts used in a synergistic combination. Also the production of hyaluronidase by the tester strain P. acnes (ATCC 11827). The combination and some other active plants shown in the study should be further investigated as possible novel medicinal agents against acne vulgaris.Dissertation (MSc)--University of Pretoria, 2014.
National Research Foundation (NRF)
Plant Science
MSc
Unrestricted
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Yu, Xiaozhang, e 于曉章. "Uptake, assimilation and toxicity of cyanogenic compounds in plants". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B41634159.
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Laverty, Edward. "The molecular basis of gene expression variability in transgenic tobacco plants". Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5238/.
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An extensive investigation into and charactaisation of factors influencing transgene expression following introduction of the transgoie into tobacco via Agrobacterium- mediated transformation was carried out. Characterisation of material supplied at the outset of this project revealed that this material was unacceptable for further analysis. It was thus deemed necessary to obtain large populations of transgenic tobacco heterogenous for levels of transgene expression. Characterisation of these populations (CaMV-lecA and ssRubisco-lecA plants) showed that all plants fell into one of four segregation classes based on segregation of the kanamycin-resistance selectable marker. Results showed that the majority of regenerants contained multiple nptII-containing inserts, while the presence of one or two such inserts was also found, albeit at a much lower frequency. Segregation analysis based on detection of the lecA transgene agreed, in the majority of cases, with these results. However, in a few cases it was found that data obtained from both segregation analyses did not agree, with the presence of a single lecA-containing transgene being detected in plants shown to contain two copies of the nptII-contaning transgene. This result indicates the occurrence of T-DNA rearrangement either within the tobacco genome or during T-DNA transfer and integration. Southern blot analyses allowed a detailed characterisation of T-DNA structure, copy number and number of integration sites to be undertaken. Results from these analyses revealed a higher frequency of T-DNA rearrangement within plants containing multiple inserts. However, such rearrangements did not correlate with a significant reduction in levels of transgene expression since all detected rearrangements were found to occur at or towards the left hand border of the T-DNA, that border distant to the lecA transgene. Plants containing more than one T-DNA were also frequently found to contain these T-DNAs arranged as an inverted repeat at a single locus although no significant relationship between copy number and the presence of such structures was found. Correlating transgene expression levels, as determined by radioimmunoassay-based quantitation of lectin protein in tissues of transgenic plants, with T-DNA copy number, organisation and structure revealed no significant relationship. It is thus feasible to conclude that the major contributory factor influencing levels of transgene expression is the location of T-DNA integration within the plant genome. Subsequent work concerned with investigating the nature of those integration site-specific factors i.e. 'position effect' indicated a possible role for methylation-induced modulation of gene expression. Results presented in this thesis provide an insight into the fate of transgenes following introduction into the plant genome and clearly demonstrate the importance of further exploring the molecular mechanisms underlying transgene expression variability.
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Rawahy, Salim Ali 1951. "EFFECT OF SODIUM-CHLORIDE, SODIUM-SULFATE AND CALCIUM-CHLORIDE SALTS ON NITROGEN AND PHOSPHORUS UPTAKE BY TOMATO PLANTS (SALINITY, OSMOTIC PRESSURE, SPECIFIC ION EFFECT)". Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/275527.
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Bao, Jiao Lin. "The antitumor effect of Forsythiae Fructus and its underlying mechanisms". Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3690828.
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Cooke, Susan Jill. "The effect of plant UV-B absorbing compounds on life history traits and reproductive performance in variable UV-B environments". Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=620.
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Thesis (Ph. D.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains x, 130 p. : ill. Vita. Includes abstract. Includes bibliographical references.
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Leeson, Elspeth A. "The effect of low temperatures on some species of Chlamydomonas and Chloromonas". Thesis, Open University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236229.
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Tront, Jacqueline Marie. "Plant Activity and Organic Contaminant Processing by Aquatic Plants". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5234.
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This research explored fate of organic contaminants in aquatic plant systems through (i) experimental development of relationships to describe sorption, uptake and enzymatic processing of contaminants by plants and inhibition of aquatic plants by contaminants and (ii) incorporation of experimental relationships into a conceptual model which describes contaminant fate in aquatic plant systems. This study focused on interactions of aquatic plants L. minor and M. aquaticum with halogenated phenols. 2,4,5-trichlorophenol (2,4,5-TCP) and 2,4-dichlorophenol (2,4-DCP) are precursors for the highly toxic and heavily applied herbicides 2,4,5-T and 2,4-D and were examined in detail. Chlorophenols are generally resistant to microbial degradation, a property which may limit microbial remediation options as effective alternatives for clean up of contaminated sites.
Relationships for fundamental interactions between plants and contaminants that dictate uptake, enzymatic processing and sequestration of contaminants by aquatic plants were established. An assay which quantified production of oxygen by plants was developed to quantify plant metabolic activity and inhibition. Uptake of chlorinated phenols depended on plant activity and aqueous phase concentration of contaminant in the protonated form. Therefore, plant activity, contaminant pKa and media pH were established as critical parameters controlling rate of contaminant uptake. A conceptual model was developed which incorporated plant activity and inhibition into a mathematical description of uptake of organic contaminants by aquatic plants. The conceptual model was parameterized using experimental data delineating effect of plant activity, inhibition and speciation on contaminant uptake and the model was verified using independently gathered data. Experimentation with radio-labeled chlorinated phenols established that contaminants were sequestered internal to plants by plant enzymatic processing. 19F NMR was established as a technique to quantify transformation and conjugation products internal to plants and contaminant assimilation by plants and demonstrated that multiple metabolites containing the parent compound were present and quantifiable internal to plants. Finally, fate of plant-sequestered contaminants in an anaerobic bioassay was examined using Desulfitobacterium sp. strain Viet1.
The results of this study address the role of aquatic plants in sequestration of contaminants in surface waters that indicate the potential and limitations of use of aquatic plants in natural and engineered treatment systems.
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Tickes, Barry, e Mike Ottman. "The Effect of Phosphorus on Alfalfa Yield". College of Agriculture, University of Arizona (Tucson, AZ), 1992. http://hdl.handle.net/10150/201366.
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Wongareonwanakij, Sathaporn. "Effects of water stress and partial soil-drying on senescence of sunflower plants". Title page, contents and summary only, 1995. http://web4.library.adelaide.edu.au/theses/09A/09aw872.pdf.
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Bibliography: leaves 98-123. This thesis investigates the symptoms of leaf senescence in response to plant shoot water stress and demonstrates the effect of a non-hydraulic root signal in the senescence response of mature leaves of sunflower. The alleviation of the leaf soluble protein loss rate by excision of the root system in drying soil indicates that this signal originates in roots in dry soil and acts to promote protein loss.
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Larsson, Marie-France. "The Effect of Plants on Individuals' Stress Level in an Indoor Work Environment". Thesis, Mid Sweden University, Department of Social Sciences, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-11141.
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Many instances of sick leave can be linked to diseases caused by stress. An efficient way to counter the negative effects of stress is coping. However, trying to fit coping activities into an already busy schedule can be stressful in itself. Therefore it is interesting to study passive stress-reducing methods, for instance interaction with nature. This paper studied the effect of the presence of plants in a work-like environment on the stress level of 30 participants divided equally in a control group and a test group by measuring their heart rate. A factorial analysis of variance and a multivariate analysis of variance were used to analyze the data. Despite the heart rate of the control group being on an average 5 beats per minute higher than the test group, the difference was found not to be statistically significant. An explanation for this could be the poor reliability of heart rate as a measure of stress.
Keywords: coping, heart rate, indoors, nature, plants, stress, work
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Hoff, Ellen Torsæter. "The Effect of Restoration Treatments on the Regeneration Pathway in Alpine Seed Plants". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-15692.
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Question: How does nutrient addition and seeding affect revegetation of seed plants, and are the effects differing among the stages of the regeneration pathway? Location: Two roads restored in 2002, located in Hjerkinn firing range, in lower alpine zone of Dovrefjell, Norway.Methods: Abundance of species and functional types (dwarf shrubs, forbs and graminoids) in four stages of the regeneration pathway (seed rain, seed bank, field seedlings and established vegetation) was recorded seven years after road reconstruction in treatment plots (with nutrient addition, nutrient + seed addition and no treatment). Results: The graminoid Deschampsia cespitosa dominated the vegetation and seed rain in fertilized plots, while the seeded Festuca rubra still dominated the seeded + fertilized plots. The germinable seed bank was lowest in the seeded + fertilized treatment, while the control plots had the highest number of seedlings germinating in the field. Dwarf shrubs had a high germination rate in the field, despite low rates in the seed rain and seed bank. The highest rate of dwarf shrub seedlings was in control plots, while the frequency of dwarf shrubs in the established vegetation increased with nutrient addition. Forbs had species specific responses.Conclusions: Both treatments that included nutrients were dominated by graminoids, with a higher vegetation cover and frequency of dwarf shrubs than the control plots. While graminoids are the most efficient seed producers, they are less able to germinate and survive as seedlings. Dwarf shrubs accounted for a high proportion of germinating seedlings in the field, but the low frequencies of dwarf shrubs in the established control plot vegetation suggest either low seedling survival or an ongoing successional change. It remains to be revealed if the high recruitment of dwarf shrubs in the control plots will speed up the establishment of the typical dwarf shrub cover similar to the surrounding vegetation and hereby indicate that unassisted recovery is the fastest way to restore alpine dwarf shrub heath.
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Badiwe, Mihlali. "Effect of Fusarium oxysporum on the physiological and molecular responses of cowpea plants". The University of the Western Cape, 2017. http://hdl.handle.net/11394/5793.
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Magister Scientiae - MSc (Biotechnology)Cowpea is a tropical, drought-tolerant legume crop that is indigenous to Africa. The crop is of nutritional importance to both animals and humans as part of their diet. Stress to crop plants is defined as any factor that negatively influences the growth and reproduction of a plant below the capabilities of the genotype.
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Bezuidenhout, Johannes Jacobus. "Elucidating the dual physiological induced effect of gliotoxin on plants / Johannes Jacobus Bezuidenhout". Thesis, North-West University, 2011. http://hdl.handle.net/10394/6945.
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Fungi and Oomycetes represent the two most important groups of eukaryotic plant pathogens. Besides chemical and physical control of these pathogens, biological control is an approach enjoying increasingly more focus. One of the biological agents increasingly employed in biological control of plant pathogenic fungi is ironically the fungus Trichoderma, more specifically Trichoderma harzianum. Besides control of the fungal plant pathogens, another interesting aspect observed when plants are treated with Trichoderma harzianum are effects such as complete and even stand of plants, faster seed germination, increases in plant height and overall enhanced plant growth. Though there have been various studies on this effect, almost no research has yet been conducted to elucidate the mechanism by which these effects occur. In particular, effects such as faster seed germination suggest that Trichoderma harzianum produces a metabolite that may mimic the plant growth hormone gibberellic acid. Through an evaluation of the various metabolites produced by Trichoderma harzianum; gliotoxin seemed structurally most similar to gibberellic acid. To verify that gliotoxin can indeed serve as an analogue for gibberellic acid and elicit similar physiological responses in plants, a two–pronged approach was followed.
Firstly, molecular similarity evaluation through common pharmacophore evaluation was conducted, followed by docking simulations into the recently discovered receptor for gibberellic acid. Common pharmacophore evaluation between gibberellic acid and gliotoxin showed successful alignment of gliotoxin into the gibberellic acid based pharmacophore space. Furthermore, docking simulations further strengthened this by the similarity in docking scores calculated and the similar poses of the ligands (gliotoxin and gibberellic acid) in the receptor space. However, similarity in pharmacophore alignment and docking simulation results only suggest that gliotoxin should be able to occupy the receptor space, but it is not a guarantee that similar physiological responses will be elicited.
In the second part of the project, the ability of gliotoxin to elicit similar physiological responses in plants to gibberellic acid was investigated. For this, a–amylase induction; plant emergence and height; and chlorophyll fluorescence were compared for both gliotoxin and gibberellic acid treatments. In terms of a–amylase induction, gliotoxin was able to induce production of the enzyme as visualised by starch–containing native gel electrophoresis (zymograms). Gliotoxin induced the strongest response at a 10–6 M dilution which is typically the range expected for hormones in biological systems in de–embryonated seeds of Phaseolus vulgaris. Gibberellic acid was able to induce the strongest response at a 10–7 M dilution. In essence, similar physiological responses were observed. In terms of plant emergence and plant height, treatment with gliotoxin or gibberellic acid resulted in plant emergence a day earlier than the untreated control. However, even though there were slight differences in plant height favouring the gliotoxin or gibberellic acid treated plants, the differences were not statistically significant. Thus, in this regard similar responses were again observed for both gliotoxin and gibberellic acid treatments. In the final evaluation the effect of gliotoxin and gibberellic acid treatments on the chlorophyll fluorescence of mature plants was investigated. Overall, both gliotoxin and gibberellic acid elicited beneficial effects on plant vitality, expressed through PI(Abs) with the gliotoxin treatment performing better than the equivalent gibberellic acid treatment.
Overall, the physiological tests demonstrated that gliotoxin can indeed elicit similar positive physiological responses to gibberellic acid in Phaseolus vulgaris. Furthermore the test used in this project can serve as a standard evaluation bench for screening for gibberellic acid analogues on a laboratory scale before larger scale field trials are considered.Thesis (Ph.D. (Microbiology))--North-West University, Potchefstroom Campus, 2012.
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Aslin, Christopher M. "The effect of speciation on cadmium uptake and resultant phytochelatin synthesis in plants". Thesis, Kingston University, 1997. http://eprints.kingston.ac.uk/20602/.
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The pollution of agricultural land with heavy metals occurs as a result of industrial activities such-as metal mining and the application of sewage sludge to the land. Regulations concerning the maximum permissible levels of heavy metals in soils of agricultural use relate only to total concentrations, not to the chemical nature (speciation) of the metal. Bioavailability and toxicity of the metal to the plant are governed by speciation. The overall aim of the research was to investigate heavy metal plant uptake with respect to metal speciation in the growing media. Plants have been shown to possess a unique ability to adapt rapidly and evolve tolerance to toxic and potentially lethal levels of heavy metals. To alleviate the stress imposed by heavy metal exposure, plants synthesize metal-binding polypeptides termed 'Phytochelatins'. Phytochelatin synthesis is thought to act as the detoxification mechanism in plant forms, analogous to metallothionein synthesis in animals. The project involved growing Zea mays plants under carefu.lly controlled conditions - the first stage was to design and build a unit to provide a constant light and temperature source. Plant symptoms were monitored and extraction and storage procedures investigated. Various methods for the isolation and purification of phytochelatins were studied in order to determine the most effective process for their quantification. The equilibrium speciation of the aqueous growing media was computed using a sophisticated computer modelling program, after an extensive thermodynamic database was constructed for the nutrient solution components. The uptake of cadmium, and the resultant Phytochelatin synthesis, has been studied in relation to the equilibrium speciation of the growing media. Cadmium was used as the toxicant, since this has been shown to be the greatest inducer of Phytochelatins. Recently several different purification methods have been documented. Hence a major part of the study has been the development of the optimum procedures for extraction, isolation and separation of Phytochelatins from 'Zea mays' primary roots.
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Hillenbrand-Nowicki, Cathy. "The effect of plants on human perceptions and behavior within an interior atrium". Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/41917.
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Plants are frequently used as design components for various types of interior settings. Design professionals may specify plants because of a subconscious awareness of the human need for natural contact, or as in may cases, such as in a "sunspace", because it is traditional to do so. Past studies by behavioral and horticulture researchers have documented human preference for plants, and have shown that plants positively affect people psychologically, but little research has been done to determine whether the use of plants in interior environments can influence human behavior.
Interior plantscaping is a vital and expanding type of agribusiness, with millions of dollars being spent each year to install and maintain plants specified by design professionals. Plants are frequently used for clients in industry, health care, hospitality, retail, education, and in personal residences. Demonstrating that plants influence human physical behavior in interior environments would increase their value as interior design components, and provide a powerful sales tool to the plantscaping industry. Because of the potential importance of understanding more about the influence of plants in interior spaces on human behavior, this research examines whether user behavior patterns and spatial perceptions can be changed by the simple addition of interior plantscaping.
This study was conducted to determine whether the introduction of trees and plants into an underutilized area of a newly constructed interior atrium would affect user perceptions of, and/or behaviors in the space. User perceptions of and activities within the atrium were recorded on questionnaires and behavioral maps, both before and after the installation of Ficus trees and Chinese Evergreen plants. Surveys were used to collect demographic information, suggestions for improving the atrium, and to determine user perceptions via the use of 13 polar adjective pairs on a six point semantic differential scale. Maps were used to record user behaviors on the lower atrium level where the plants were placed.
The majority of data were analyzed descriptively by frequencies and percentages. Semantic differential analysis was done using two-tailed t-tests at p = .05. T-tests did not prove to be significant. There was mean movement of perceived perceptions from pre- to post-test. User behavior on the lower atrium level appeared to be affected by plant installation. A preference was shown for napping under the trees, and users spent more time on that atrium level when the trees and plants were present.Master of Science
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Deka, Priyanka. "The Effect of Zinc Oxide Nanoparticles on Plants, and on Host-Pathogen Interactions". Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/29270.
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Zinc oxide nanoparticles (ZnO NPs) are a type of engineered nanomaterial that is currently being explored for use in different aspects of agriculture. So far, research on this area is limited to evaluating the phenotypical responses of plants to a high concentration of the NPs which is realistically not feasible in the actual environment. This research aims to investigate the molecular-level interactions between ZnO NPs and plants, together with another significant component of the environment, a fungal plant pathogen. Prior to studying these molecular-level interactions, the uptake of ZnO NPs in planta was validated using a fluorescent zinc ion sensor, Zinpyr-1 and a zinc ion chelator, TPEN in confocal laser scanning microscopy (CLSM) and Transmission Electron Microscopy (TEM). Phenotypical effects were studied in soybean plants exposed to environmentally relevant concentrations of ZnO NPs and bioaccumulation of zinc was studied in seeds of soybean and other soy products. The next phase of this research focused on investigating the physiological responses of plants exposed to ZnO NPs. This was achieved by elucidating the complete transcriptome of the plants using a Next Generation sequencing (NGS) platform, RNA seq. A significant part of this research emphasized on exploring the effects of ZnO NPs on host-pathogen interactions. The model monocot plant, barley was used in this study, together with a necrotrophic pathogen, Pyrenophora teres f. teres (Ptt). The barley line which was used, CI5791 is resistant to the disease Net Form Net Blotch (NFNB), caused by Ptt. Rapid responses of plants to ZnO NPs were observed that subsided at the later time-points, whereas the heightened responses to the pathogen alone (P) and combined application (ZnO NP + P) persisted. Exposure to ZnO NPs also induced transcriptional reprogramming in the Ptt inoculated plant that resulted in compromised immunity in the otherwise resistant barley, due to the persistence of salicylic acid (SA)-related genes. In ZnO NP-exposed Arabidopsis thaliana, the effects were contradictory. From the barley and Arabidopsis expression data, it could be concluded that both species react differently to ZnO NPs, giving a glimpse of the differential responses that ZnO NPs may elicit in different plant species.USDA-NIFA
National Science Foundation (NSF)
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Chappelka, Arthur H. "The combined effects of ozone, sulfur dioxide and simulated acid rain on the growth of three forest tree species". Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/74726.
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Nine-week-old yellow-poplar and green and white ash were exposed to various concentrations of O₃ (0.00 to 0.15 ppm) and/or SO₂ (0.08 ppm), 4 hr/d, 5d/wk in combination with simulated rain (pHs 5.6, 4.3, 3.0), 1 hr/d, 2 d/wk, for 5 or 6 wk under controlled laboratory conditions. Pollutant exposures resulted in alterations in seedling biomass accumulation, growth rates, changes in carbon allocation among plant parts and modification in physiological processes associated with gas exchange. Ozone (0.010 ppm) and SO₂ together caused a significant decrease in height growth and biomass and an increase in leaf area ratio (LAR) in yellow-poplar. Ozone and SO₂ exposures resulted in linear decreases and increases, respectively, in root dry weight, leaf area increase, relative growth rates of all yellow-poplar plant parts and unit leaf rate with decreasing rain pH. Chlorophyll content increased in both O₃ and SO₂ treatments with increasing rain acidity. In green and white ash experiments height growth was inhibited by O₃, SO₂ and O₃ + SO₂ for green ash, whereas only leaf dry weight was decreased by O₃ exposure in white ash. Decreasing rain pH resulted in linear decreases in root/shoot ratio (RSR) and LAR, for white ash. In green ash, a quadratic response to rain pH occurred with these growth variables. Ozone and O₃ + SO₂-treated green ash exhibited a significant quadratic response in leaf weight ratio with increasing rain acidity. Leaf area ratio and RSR exhibited linear increases and decreases, respectively, for O₃ and rain acidity. In SO₂-treated white ash with increasing white ash and yellow-poplar seedlings exposed to various O₃ concentrations and simulated rain for 5 and 6 weeks, respectively, increasing O₃ concentrations caused linear decreases in height and biomass of white ash. Linear decreases in root growth rate and biomass and RSR occurred with decreasing rain pH, across O₃ treatments. Ozone (0.05 or 0.10 ppm) caused linear decreases in these variables in combination with increasing rain acidity. For yellow-poplar, increasing O₃ concentrations caused linear increases in RSR and specific leaf area. At 0.05 and 0.10 ppm O₃, stem and leaf biomass, their relative growth rates and leaf area all decreased with decreasing rain pH. Ozone (0.10 ppm) exposure caused a decrease in stomatal conductance, and decreasing variable. rain pH resulted in a linear decrease in this A linear decrease in net photosynthesis also occurred with increasing rain acidity in O₃-treated (0.10 ppm) plants. These results demonstrate that gaseous pollutants in combination with simulated acid rain can have detrimental effects on growth of three forest tree species, under controlled laboratory conditions.Ph. D.
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Zhang, Chao. "Anti-liver cancer effect of polyphyllin VII and its molecular mechanisms". Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3690802.
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Genc, Yusuf. "Screening for zinc efficiency in barley (Hordeum vulgare L.)". Title page, table of contents and summary only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phg324.pdf.
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Bibliography: leaves 229-250. The aims of the study were to develop a reliable method for screening for Zn efficiency as an alternative to the current field-based methods, and to determine the extent of genotypic variation in tolerance to Zn deficiency in barley.
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Gillman, Michael Philip. "The effect of grazing by gastropods on vegetation dynamics in early secondary succession". Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253228.
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