Dissertations / Theses on the topic 'Ecophysiology'
To see the other types of publications on this topic, follow the link: Ecophysiology.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Ecophysiology.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Sobral, Maria Paula de Oliveira. "Ecophysiology of Ruditapes decussatus." Doctoral thesis, FCT - UNL, 1995. http://hdl.handle.net/10362/1154.
Full textAbstract:
The physiological responses of the clam R. decussatus from the Ria Formosa, southern Portugal, were examined in relation to normoxia, hypoxia (11, 6, 3 and 1.2 kPa) and anoxia; acute elevation of temperature
(at 20, 27 and 32 °C), and its effect on the resistance to air exposure (at 20, 28 and 35 °C); current velocity (0.6, 3, 8 17, 24 and 36 cm. s-1) and turbidity (10, 100 and 300 mg. l-1 dry weight of particulate matter), and the efficiency of this species in retaining particles of different size (at 10
and 100 mg. l-1); and to copper contamination considering both short-term acute exposure to high levels (0.1-10 mg Cu. l-1) and chronic environmental levels (0.01 mg Cu. l-1).
Clearance rates, respiration rates, absorption efficiency and excretion
rates were assessed through the physiological energetics in terms of the energy budget and scope for growth (SFG).
Stress independent respiration rates (R) and clearance rates (CR) were observed in relation to hypoxia down to 12 kPa and 6 kPa, respectively.
Anoxic rates were 3.6 % of normoxic rates. Scope for growth was greatly reduced under extreme hypoxia (14 % of SFG in normoxia).
Respiration rate was temperature independent in the range 20-32 °C but the decline in clearance rate resulted in negative SFG at 32 °C. Gaping during air exposure and the maintenance of faster aerobic metabolism led
to 100 % mortality in 20 hours at 35 °C, 4 days at 28 °C and 5 days at 20 °C.
Low current velocities (≤ 8 cm. s-1) supported high clearance rates. Shear
stresses ≥ 0.9 Pa induced sediment movement and disturbed the feeding processes resulting in decreased clearance rates (at 36 cm. s-1, is 10 % of maximum CR). The observed ability of jetting out depleted water at a different level than the one of the inhalant current results is an important adaptation of clams to the slow currents of sheltered environments.
Ingestion at high seston concentrations (> 100 mg. l-1) is controled by reducing
the amount filtered, lowering CR (to 30 % of CR at low seston loads) and producing pseudofeces.
Observed efficient retention of particles (70-100 %) in the range 3 to 8 μm is beneficial when algal cells are diluted by fine silt particles as it is likely to occur in the clams natural environment.
R. decussatus in the short term escaped the exposure to copper by valve closure and therefore acute tests are not applicable to adult clams of this species. At environmental levels chronic exposure to copper did not induce lethal effects during the exposure period (20 days), but scope for growth
was reduced to c. 30 %, indicating sustained impairment of physiological functions.
The sensitivity of the physiological energetics and the integrated scope for
growth measurement in assessing stress effects caused by natural environmental factors was highlighted.
2
Gabriel, Rosalina Maria de Almeida. "Ecophysiology of Azorean forest bryophytes." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326158.
Full text
3
Rottberger, Julia [Verfasser]. "Ecophysiology of mixotrophic flagellates / Julia Rottberger." Konstanz : Bibliothek der Universität Konstanz, 2013. http://d-nb.info/1049393643/34.
Full text
4
Wetson, Anne Margaret. "Ecophysiology of the halophyte Suaeda maritima." Thesis, University of Sussex, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488565.
Full textAbstract:
Suaeda maritima is a widely occurring annual halophyte that experiences the fluctuating salinity and hypoxia of tidal cycles on salt-marshes. During dormancy, seeds survive in saline, hypoxic mud to germinate when spring-time temperatures reach about 15 °C. Plants of Suaeda maritima have wide salinity tolerance but little work has been published regarding interlinked waterlogging. The effects of saline waterlogging on growth and ion accumulation were investigated in tanks in a glasshouse where tidal flow was simulated and in aerated and hypoxic saline culture solution in a controlled environment cabinet.
5
Roast, Stephen Derek. "Ecophysiology of Neomysis integer (Mysidacea: Peracarida)." Thesis, University of Plymouth, 1997. http://hdl.handle.net/10026.1/2746.
Full textAbstract:
Neomysis integer (Leach) (Peracarida: Mysidacea) is a common component of the hyperbenthos of Western European estuaries, and this study focused on the ecophysiology and ecotoxicology of this mysid. Behavioural and physiological responses of N. integer to physical and chemical variables (current velocity, substratum type, temperature and salinity) were measured in the laboratory to gain better understanding of how this mysid maintains position in estuaries. Current velocity was the most important factor controlling position maintenance, and N. integer had a maximum swimming speed of c. 9cm sˉ¹. Position maintenance was facilitated by a muddy substratum and was not affected by salinity. Oxygen consumption and feeding rates of N. integer increased with increasing temperature but, whilst oxygen consumption decreased with increasing salinity, feeding rate increased. Male mysids consumed oxygen at a higher rate than females, however, there was no difference in the feeding rates of males and females. The acute toxicity of two organophosphate pesticides (chlorpyrifos and dimethoate) to N. integer was examined, and 96h LC50 values of 0.13µg chlorpyrifos Lˉ¹ and 0.54mg dimethoate Lˉ¹ were estimated. Sub-lethal exposure to chlorpyrifos led to an increased rate of oxygen consumption and decreased feeding rates compared with control animals. In addition, chlorpyrifos exposure led to disrupted behaviour of N. integer, including hyperactivity and decreased maximum swimming speed. The results are discussed in terms of the behaviour and physiology of N. integer in response to natural and anthropogenic physical and chemical variables in the natural environment. The potential of N. integer as a toxicity testing species, and the sublethal responses used in the study, are critically assessed.
6
Birk, Matthew A. "Ecophysiology of Oxygen Supply in Cephalopods." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7265.
Full textAbstract:
Cephalopods are an important component of many marine ecosystems and support large fisheries. Their active lifestyles and complex behaviors are thought to be driven in large part by competition with fishes. Although cephalopods appear to compete successfully with fishes, a number of their important physiological traits are arguably inferior, such as an inefficient mode of locomotion via jet propulsion and a phylogenetically limited means of blood-borne gas transport. In active shallow-water cephalopods, these traits result in an interesting combination of very high oxygen demand and limited oxygen supply. The ability to maintain active lifestyles despite these metabolic constraints makes cephalopods a fascinating subject for metabolic physiology. This dissertation focuses on the physiological adaptations that allow coleoid cephalopods to maintain a balance of oxygen supply and demand in a variety of environmental conditions.
A critical component of understanding oxygen supply in any animal is knowing the means of oxygen delivery from the environment to the mitochondria. Squids are thought to obtain a fairly large portion of their oxygen via simple diffusion across the skin in addition to uptake at the gills. Although this hypothesis has support from indirect evidence and is widely accepted, no empirical examinations have been conducted to assess the validity of this hypothesis. In Chapter 2, I examined cutaneous respiration in two squid species, Doryteuthis pealeii and Lolliguncula brevis, by using a divided chamber to physically separate the mantle cavity and gills from the outer mantle surface. I measured the oxygen consumption rate in the two compartments and found that, at rest, squids only obtain enough oxygen cutaneously to meet demand of the skin tissue locally (12% of total). The majority of oxygen is obtained via the traditional branchial pathway. In light of these findings, I re-examine and discuss the indirect evidence that has supported the cutaneous respiration hypothesis.
Ocean acidification is believed to limit the performance of squids due to their exceptional oxygen demand and pH-sensitivity of blood-oxygen binding, which may reduce oxygen supply in acidified waters. The critical oxygen partial pressure (Pcrit), defined as the PO2 below which oxygen supply cannot match basal demand, is a commonly reported index of hypoxia tolerance. Any CO2-induced reduction in oxygen supply should be apparent as an increase in Pcrit. In Chapter 3, I assessed the effects of CO2 (40 to 140 Pa) on the metabolic rate and Pcrit of two squid species: Dosidicus gigas and Doryteuthis pealeii. Carbon dioxide had no effect on metabolic rate or hypoxia tolerance in either species. Furthermore, considering oxygen transport parameters (e.g. Bohr coefficient, blood P50) and blood PCO2 values from the literature, I estimated an increase in seawater PCO2 to 100 Pa (≈1000 μatm/ppmv) would result in a maximum drop in hemocyanin-O2 saturation by 6% at normoxia and a Pcrit increase of ≈1 kPa (≈5% air saturation) in the absence of active extracellular pH compensation. Such changes are unlikely given the capacity for acid-base regulation in many cephalopods. Moreover, this estimated change is within the 95% confidence intervals of the Pcrit measurements reported here. Squid blood-O2 binding is more sensitive to pH than most other marine animals measured to date. Therefore, the lack of effect in squids suggests that ocean acidification is unlikely to have a limiting effect on blood-O2 supply in most marine animals.
The pelagic octopod, Japetella diaphana, is known to inhabit meso- and bathypelagic depths worldwide. Across its range, individuals encounter oxygen levels ranging from nearly air-saturated to nearly anoxic. In Chapter 4, we assessed the physiological adaptations of individuals from the eastern tropical Pacific (ETP) where oxygen is extremely low. Ship-board measurements of metabolic rate and hypoxia tolerance were conducted and a metabolic index was constructed to model suitable habitat for aerobic metabolism. I found that animals from the ETP had a higher metabolic rate than animals from more oxygen-rich habitats. Despite their higher oxygen demand, they maintained better hypoxia tolerance than conspecifics from oxygen-rich Hawaiian waters. Furthermore, I found that hypoxia tolerance in Japetella has a reverse temperature dependence from most marine ectotherms, a characteristic that uniquely suits the physical characteristics of its oxygen-poor environment. Even with their high tolerance to hypoxia, the OMZ core likely has insufficient oxygen supply to meet the basal oxygen demand of Japetella. Despite the limited aerobic habitat in this region, species abundance was comparable to more oxygenated ocean regions, suggesting that physiological or behavioral plasticity such as altered hypoxia tolerance or hypoxic avoidance in this globally-distributed species is sufficient to maintain species fitness in this extreme environment.
These findings contribute towards our understanding of the impacts of climate change on cephalopod physiology and biogeography. The study of environmental physiology provides a mechanistic basis for the understanding and prediction of ecological responses to climate change.
7
Miyazawa, Kae. "Comparative ecophysiology of North American spruce species." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30705.
Full textAbstract:
An ecophysiological comparison among species was conducted to investigate the possible factors controlling the distribution of North American spruce (Picea) species, especially with regard to the possible influence of global change. The seedlings of 8 North American spruce species were grown in a growth chamber, with half of them being given an episodic 'increased temperature and drought' stress treatment. Trait values among species, particularly growth analysis components, were compared and related to climatic variables associated with the geographical range of the species. Relative growth rate (RGR) and specific leaf area (SLA) were positively correlated with latitude, and the leaf weight ratio (LWR) variation negatively with the dryness of species' natural ranges. All these relationships hold with both messed and unstressed seedlings, even thou seedling response to the stress was significant. The SLA-latitude and LWR-dryness relationships are likely to have ecological significance, and this indicates that foliage stricture (SLA) and allocation (LWR) play important roles determining a species range along temperature and dryness gradients.
8
Tyler-Walters, Harvey. "The genetics and ecophysiology of Lasaea SP." Thesis, Bangor University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253320.
Full text
9
Stengel, Dagmar Brigitte. "Ecophysiology of growth and photosynthesis of Ascophyllum." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241496.
Full text
10
Morritt, D. "The ecophysiology of selected talitroidean amphipods (Crustacea:Amphipoda:Talitroidea)." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233861.
Full text
11
Saluzzi, Liliana. "Ecophysiology of cellulolytic bacteria in the rumen." Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU542848.
Full textAbstract:
The rumen microbial populations involved in the degradation of barley straw and clover/ryegrass forage during incubation in sacco were studied by the analysis of microbial phospholipids. The results suggested that the adherent populations differed from those in the liquid phase of the rumen contents, and that the microorganisms attached to barley straw differed from those attched to clover/ryegrass. In addition, the population adherent to barley straw appeared to change during the degradative process. The latter point was supported by observations using the electron microscope. When barley straw was incubated in vitro with Ruminococcus flavefaciens prior to incubation in the rumen, phospholipid analysis suggested that R.flavefaciens persisted during 72 h incubation in the rumen, although as a declining component of the mixed population. Ruminococcus flavefaciens was possibly displaced or other 'free' sites of attachment were occupied by different species. The in vitro incubation of Ruminococcus flavefaciens and Fibrobacter succinogenes on clover/ryegrass and barley straw showed that the presence of F.succinogenes reduced the population size of R.flavefaciens and the degradability of clover/ryegrass suggesting a competitive or antagonist interaction betweeen these species. The analysis of phospholipid marker components and viable counts showed that R.flavefaciens rapidly outgrew F.succinogenes. Ruminococcus flavefaciens and Fibrobacter succinogenes differed in the quantity and nature of the soluble plant components that accumulated in the culture liquids. After training Ruminococcus flavefaciens strain 17 to grow on different forages, adaptation through enhanced substrate degradation was detected when cultures were grown repeatedly on ryegrass. Significant increases in specific xylanase and beta-xylosidase activities were detected. It is concluded that the increase in dry matter solubilization and enzyme activities during prolonged subculture on ryegrass probably resulted from forward mutations.
12
Johnston, Jason Clarence. "The Effects of Forest Management and Food Availability on the Ecophysiology of Pre-Breeding and Breeding Hermit Thrushes (Catharus guttatus)." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/JohnstonJC2007.pdf.
Full text
13
Chuba, David. "A comparative study of the distribution of C₃ and C₄ species of Cyperaceae in South Africa in relation to climate." Bachelor's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/25990.
Full textAbstract:
In this study the contribution of the climatic factors such as temperature, altitude, and mean annual precipitation as well as phylogeny to the determination of the distribution of C₃ and C₄ genera of Cyperaceae in South Africa has been investigated. Multiple regression analysis was used to determine the climatic factor that best predicted percent C₄ distribution. To see if the C₄ syndrome was influenced by taxonomy, the percentages of C₄ species was determined for each of the subtribes and genera. The results show that the relationship between the climatic factors and percentage of C₄ Cyperaceae species is similar to what has been found for the grasses (Vogel et al., 1978). However C₃ species of Cyperaceae seem to be abundant in most parts of South Africa. Only minimum growing season temperature showed significant correlation (P = 0.000391) with percentage C₄. The presence of the C₄ syndrome is shown to have some consistency within subfamilies, tribes and genera.
14
Miyazawa, Kae. "Comparative ecophysiology of North American spruce species (Picea)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0030/MQ64409.pdf.
Full text
15
Kiko, Rainer [Verfasser]. "Ecophysiology of Antarctic sea-ice meiofauna / Rainer Kiko." Kiel : Universitätsbibliothek Kiel, 2009. http://d-nb.info/1019811021/34.
Full text
16
Rodriguez-Acosta, Maricela. "Ecophysiology and genetics of drought tolerance in Populus." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436975.
Full text
17
Davis, Phillip Andrew. "The ecophysiology and gas vesicles of Planktothrix spp." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393953.
Full text
18
Lambourne, Gail. "The ecophysiology of Gloeotrichia echinulata in Blashford Lake." Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265422.
Full text
19
Almeida, Edmilson Igor Bernardo. "Shading in ecophysiology, production and cuttings red pitaya." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=14224.
Full textAbstract:
nÃo hÃEm pomares comerciais de pitaia vermelha, no CearÃ, Ã comum a presenÃa de plantas com cladÃdios amarelados, principalmente nas Ãpocas mais quentes do ano. Diante disso, realizou-se um estudo com o intuito de avaliar a interferÃncia do sombreamento sobre o crescimento, anatomia, pigmentos fotossintÃticos, trocas gasosas e produÃÃo de pitaia vermelha. O delineamento experimental foi em blocos casualizados (DBC), com cinco tratamentos, cinco repetiÃÃes e duas plantas por parcela. Os tratamentos foram constituÃdos pelos nÃveis de sombreamento: pleno sol, 35, 50; 65 e 80% de sombreamento. As avaliaÃÃes foram divididas em duas etapas (180 e 365 dias), de modo a observar o efeito dos tratamentos sobre o crescimento inicial e o primeiro ciclo produtivo da cultura. A pitaia vermelha, inicialmente (aos 180 dias), apresentou melhor desempenho sob condiÃÃes de sombreamento, especialmente a 35% de sombra. No entanto, ao decorrer do seu ciclo, as plantas cultivadas a pleno sol foram as mais produtivas, com nÃmero de frutos, duas vezes superior Ãs sombreadas. Para as condiÃÃes edafoclimÃticas de Fortaleza (CE) recomenda-se a produÃÃo de mudas em condiÃÃes sombreadas de 35% e a implantaÃÃo do pomar de pitaia vermelha a pleno sol.
In commercial orchards red dragon fruit, CearÃ, is common the presence of plants with yellow cladodes, especially in the warmer seasons. Therefore, we carried out a study in order to evaluate the effect of shading on growth, anatomy, photosynthetic pigments, gas exchange and production of red pitaya. The experimental design was randomized blocks (DBC), with five treatments, five replicates and two plants per plot. The treatments were constituted by shading levels: full sun, 35, 50; 65 and 80% shading. The evaluations were divided into two stages (180 and 365 days) in order to observe the effect of treatments on initial growth and production cycle of the first crop. The red dragon fruit, initially (at 180 days), performed better under shade conditions, especially the 35% shade. However, the course of its cycle, plants grown in full sun were the most productive, with number of fruits, twice the shaded. To soil and climatic conditions of Fortaleza (CE) is recommended to grow seedlings in shaded conditions 35% and the implementation of the red dragon fruit orchard in full sun.
20
Sedlacek, Christopher James. "The Ecophysiology of Nitrosomonas sp. Is79." Miami University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=miami1437695996.
Full text
21
Brown, Richard P. "Microevolution and ecophysiology of Canary Island skinks (Chalcides)." Thesis, University of Aberdeen, 1990. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU031703.
Full textAbstract:
Within-island geographic variation in three character systems (body dimensions, scalation, colour pattern) and in life history is described in the Gran Canarian skink (Chalcides sexlineatus). Numerical methods used to describe patterns of geographic variation include contouring, principal components analysis, multiple group principal components analysis and canonical variates analysis. The primary patterns of geographic variation are north-east/south-west clines, although altitudinal variation is also evident in some characters. Several hypothesized causes of the variation are erected and tested using Mantel Tests and partial correlation. This points to lush/arid ecotone adaptation as the cause. A suggestion by previous workers that there are two species on the island is rejected. Patterns of geographic variation in Chalcides viridanus on the neighbouring island of Tenerife are described and tested against hypotheses using similar methods. Tenerife shows similar lush/arid variation to that in Gran Canaria. Parallel patterns of geographic variation in morphology are found, most notably in colour pattern. This strongly suggests that adaptation to current ecological conditions, rather than ancient population vicariance, is the cause. Geographic variation in anti-predator strategy can explain the colour pattern microevolution. Ecological differences between populations of C. sexlineatus are investigated to elucidate the actual selection pressures acting on different aspects of the animals' morphology. Some thermoregulatory and also dietary and prey size differences are found among populations. Daily energy expenditure and water flux are compared among skinks from northern and southern populations in the field, using the doubly-labelled water technique. Between-population differences in energy expenditure can be attributed to body size differences.
22
Brooks, Steven John. "The osmoregulation of selected gammarid amphipods." Thesis, Nottingham Trent University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272439.
Full text
23
Harris, Sue-Re. "Phosphorus sensitivity in species of Proteaceae (Protea obtusifolia, Leucadendron coniferum and Leucadendron salignum) from different soil habitats : possible candidates for growth on former agricultural soils high in P." Bachelor's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/26186.
Full textAbstract:
The phosphorus (P) uptake capacities and tolerance to high P of three Proteaceae species from acid (Leucadenron coniferum, Leucadendron salignum) and alkaline (Protea obtusifolia, Leucadedndron meridianum) soils in the Cape Floristic Region (CFR) were compared. These species were also investigated as potential candidates for growth on nutrient enriched, post-agricultural soils. In parallel, two crop plant species (Lupinus albus, with cluster roots; and L. angustifolius, without cluster roots) were also compared. The cluster-root forming species (L. albus) was more sensitive to higher P levels and showed toxicity in terms of photosynthesis, efficiency of PSII, transpiration and stomatal conductance. Growth, gaseous exchange and efficiency of photosystem II (as a measure of stress) were determined at 1, 10 and 100 μg P g⁻¹ sand for both lupins and Proteaceae. Kinetics of P uptake (in hydroponics) was determined at a range ( 4 to 2000 μM P) of P concentrations. Phosphorus sensitivity was relatively high in Ld. coniferum as evident from reduced growth, net photosynthetic rate, stomata} conductance and transpiration rates. Protea obtusifolia showed the least sensitivity to increased phosphorus concentrations under acidic and native alkaline conditions. The inability to regulate P uptake rates at elevated phosphorus concentrations and excessive P accumulation were major determinants of P sensitivity. The relatively higher P sensitivity of Lupinus albus compared to L. angustifolius is likely related to the efficient P uptake by cluster roots in the former.
24
Williams, Stephanie. "Leaf nutrient draw back as a strategy for tree grass co-existence in the savanna biome." Bachelor's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/25877.
Full textAbstract:
As there is still a major debate on how trees and grasses manage to coexist in the savanna biome, the niche separation by phenology hypothesis (Scholes and Archer 1997) was tested by observing the seasonal variation in carbon and nitrogen concentrations in leaves and young twigs of two deciduous species, Combretum apiculatum and Terminalia sericea. The study was carried out in the sub-tropical savanna biome in southern Kruger National Park, South Africa. Photosynthetic readings show a decrease in leaf activity towards the end of the growing season. There was no significant change in the carbon concentrations over the months for both species sampled but there was a significant decrease in leaf nitrogen for C. apiculatum. T. sericea experienced relatively no nitrogen draw back until a sudden drop at the end of June. Translocated nitrogen in C. apiculatum accumulated in large amounts in the peripheral twigs (branching order one) compared to T. sericea, where nitrogen only increased at the end of June in the same location. There was also a corresponding significant change in the carbon:nitrogen ratio in C. apiculatum, especially in the leaves, showing a decrease in palatability as nitrogen was drawn out. The results observed did not become more pronounced in site 3, which had the highest soil moisture content. Soil moisture availability therefore does not appear to influence the degree of nitrogen reabsorption from the leaves. The hypothesis proposed is that deciduous trees use stored nitrogen from their senescing leaves to leaf out earlier gaining a competitive advantage over grasses, which are waiting for nitrogen to be mineralized in the soil with the onset of the summer rain. This study therefore supports the niche separation by phenology hypothesis to explain how these two growth forms coexist in the savanna biome.
25
Mafa, Paseka. "Response of Cynodon dactylon (L.) Pers. to ammonium and nitrate nutrition." Bachelor's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/25621.
Full textAbstract:
Plants that come early in succession predominantly prefer_ ammonium form of nitrogen than nitrate. The hypothesis that Cynodon dactylon (L.) Pers., a grass in the primary succession stage would respond well when supplied with ammonium than nitrate fertiliser was tested. Seedlings of Cynodon dactylon were grown in culture solution and fertilised with either ammonium sulphate or potassium nitrate at ~ continuous concentrations of 200 ppm, 400 ppm and 600 ppm in the growth chamber. In support of my hypothesis, growth of Cynodon dactylon was greater from ammonium than nitrate nutrition in terms of aboveground and total plants yields at 200 ppm and 400 ppm and this was associated with efficient utilisation of this form of nitrogen by this species. Production from the nitrate treatments was restricted and showed no change with increase in external nitrogen supply. Decreased dry weights from the ammonium nutrition at 600 ppm were associated with toxicity of ammonium ions in plant tissues. High levels of nitrogen measured from the nitrate treatments were associated with the soluble nitrogen that was not assimilated for yield increase by this grass, Uptake of ammonium ion was shown to result· in high of uptake phosphorus. This study shows that Cynodon dactylon has the capacity for increased growth under ammonium nutrition while this was limited in the nitrate nutrition. However, response is restricted when excessively fertilised with ammonium nitrogen.
26
Wienand, Karen Tania. "A preliminary study of the impacts of alien Acacia infestation (A saligna) on the relative rates of nitrogen and phosphorus cycling in Lowland Fynbos, southwestern Cape, South Africa." Bachelor's thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/25891.
Full textAbstract:
This study was carried out on Sand Plain Lowland fynbos at Pella from April to September 1988. Environmental factors, nitrogen and phosphorus pool sizes and mineralization processes were investigated in the surface soils (1-10cm) of 7-8 year old fynbos vegetation and an adjacent Acacia saligna (Labill.) Wendl. infestation. While there was no significant difference in soil temperature between fynbos and acacia sites, soil moisture and organic matter content was significantly higher in the acacia soils. This favoured decomposition so that soil nutrient analyses showed enrichment of the soils (higher N and P) by the acacia infestation. Soil N and P mineralization was assayed using in situ incubations. Due to their higher soil total N concentrations, acacia soils showed greater inorganic N concentrations. In both acacia and fynbos soils ammonium was the dominant N form. This was ascribed to the high soil moisture content, while the low temperatures appeared to be the factor most strongly influencing ammonium accumulation. The low nitrate accumulations even in the field incubations indicated that the nitrification process was inhibited, probably by the high soil moisture content and low temperatures. The variable patterns of inorganic P accumulation were ascribed mainly to fluctuations between microbial mineralization and immobilization. Contrary to the hypothesis that the higher soil organic matter and greater concentrations of total N and Pin acacia soils would result in higher mineralization rates, there was no significant difference in the rates of N and P mineralization between fynbos and acacia soils. Thus, it was concluded that the higher decomposition rates in acacia soils was not associated with greater mineralization rates during the wet season (period of study).
27
Manuel, Theodore Llewellyn. "Effect of soil nutrient status on stress tolerance in Proteaceae." Bachelor's thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/25615.
Full textAbstract:
Protea lepidocarpodendron grown on low, medium and high nutrient treatments exhibited the lowest, and similar evapotanspiration rates respectively over a 9 day water stress cycle (experimental period). In stressed and unstressed treatments, stomatal conductance and transpiration rates of plants grown on the low nutrient treatment was generally lower than that of plants grown on the medium and high nutrient treatments where stomatal conductance and transpiration rates were similar. Stressed plants grown on the low, medium and high nutrient treatments exhibited the lowest, intermediate and highest photosynthetic rates respectively. Stessed plants grown on the medium and high nutrient treatments exhibited a dramatic decrease in transpiration rates ands stomatal conductance from day 5 to 7, and a dramatic decrease in photosynthetic rates from day 3 to 7. Stressed plants grown on the low nutrient treatment showed a far less dramatic decrease in transpiration rate, stomatal conductance and photosynthetic rate over the 9 day period. For stressed plants, photosynthetic rates varied between 0.08-5.39 uMOLm⁻²s⁻¹, 1.17-7.48uMOlm⁻²s⁻¹ and 1.15-8.65uMOLm⁻²s⁻¹ for plants grown on low, medium and high nutient treatments respectively. Unstressed plants grown on low. medium and high nutrient treatments exhibited the lowest, highest and intermediate photosynthetic rates respectively. In all stressed treatments, photosynthetic rates showed a steady decline from day 1 to day 7, whereafter a dramatic increase occurred in the medium and high nutrient treatments, and a less dramatic increase in plants grown on the low nutrient treatment. These decreases and increases in photosynthetic rates was not parallelled in the stomatal conductance and transpiration rates of the unstressed plants. For unstressed plants, photosynthetic rates varied between 1.4s-4.4 uMOLm⁻²-s⁻¹, 1.65-6.7 uMOLm⁻²s⁻¹ and 3.42-8.76 uMoLm⁻²s⁻¹ for plants grown on low, medium and high nutrient treatments respectively. Plants grown on low nutrient treatments exhibited the highest LSW (182.3 gm⁻²), highest whole plant mass (WPM) (1.07g), followed by high (LSW=1.76 gm⁻²,WPM=0.83g) and medium (LSW=167.28 gm⁻² ,WPM=0.79g) nutrient treatments. Total plant nitrogen content was inversely related to LSW and WPM on low (3.84 mgNplant⁻¹), high (4.18 mgNplant⁻¹) and medium (5.28 mgNplant⁻¹) treatments. Root : ratio between treatments were similar.
28
Swanwick, Susanne. "Ecophysiology and production of the biocontrol agent Phlebiopsis gigantea." Thesis, Cranfield University, 2007. http://dspace.lib.cranfield.ac.uk/handle/1826/2928.
Full textAbstract:
Heterobasidion annosum, the causative agent of the disease “root and butt rot” in conifers, is ubiquitous in the environment and causes severe financial losses to the forestry industry throughout the temperate zone. The normal route of infection is as basidiospores that land on the freshly cut stump surface during thinning operations, the colonisation of the stump providing sufficient inoculum for the fungal hyphae to invade healthy roots of adjoining trees. The most successful disease control measures involve depriving the pathogen the opportunity to become established in the food source of the fresh cut stump. Frequently killing the surface of the stump with a chemical treatment does this, but there is also some success with a biocontrol method. When the antagonist Phlebiopsis gigantea, a saprophyte, is inoculated onto the stump surface it rapidly invades the tissue thus preventing the pathogen access to the resource. Environmental studies have been carried out to assess the fitness of different isolates of the antagonist relative to the pathogen. Competitiveness was affected by environmental factors; water availability, osmotic/matric potentials, temperature, nutrition, and substrate. These indicate that the antagonist is not able to suppress the pathogen under all conditions. Generally, in wet warm conditions the antagonist is dominant, ID 10:2 antagonist:pathogen, but in drier, cooler conditions the pathogen is dominant, ID 2:10 on MEA. Interactions in situ on wood discs showed the pathogen was restricted to 0-2% of the treated portion and 2-10% of the un-treated surface at 25 ºC, but at 4 ºC it colonised 2-24% of the former and 34-57% the latter. Consideration needs to be given to possible field conditions at the time of application to maximise the establishment of the antagonist. Studies have been carried out to examine potential for liquid or solid substrate fermentation systems for optimising production of P.gigantea. Liquid culture studies were variable regardless of available nutrients and ecophysiological stresses imposed, producing a maximum of 6.5 log10 CFU ml -1 . However, temporal studies on solid substrate based on Pinus sylvestris sawdust gave 8 Log10 viable oidia g -1 in the best moisture content treatments. Scale up, to 200g substrate produced similar CFUs, however increasing to 400 g showed a reduction in viable oidia, due to lack of moisture equiibration. Analyses of the endogenous reserves to identify specific quality characteristics were inconclusive. Mycelial pellets and submerged conidia produced in fermentation had increased levels of glycerol and erythritol as aw was lowered, however this was not replicated by oidia produced in solid substrate fermentation. Preservation studies, in a fluidised bed reactor showed, the survival of PG21 spores at up to 60 ºC for 20 min. Studies were carried out to analyse volatile fingerprints of antagonist and pathogen isolates using an AlphaM.O.S. electronic nose. Volatile fingerprints showed clear grouping of antagonist and pathogen isolates, as distinct from each other. With some isolates, the fingerprints of interactions were co-incidental with the antagonist. It is suggested that this novel technique could be used as a rapid screening method for potential BCAs.
29
McKendrick, Sheena Lindsay. "The ecology and ecophysiology of some British orchid species." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282858.
Full text
30
Tibbetts, Rebecca Anne. "Ecophysiology of calcium and magnesium accumulation in higher plants." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260783.
Full text
31
Luk, In, and 陸妍. "The ecophysiology and dynamic energy budget of Septifer virgatus." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206657.
Full textAbstract:
The black-ribbed mussel, Septifer virgatus, is a northern species which forms dominant bands in the mid-low levels of exposed rocky shores along the Northwest Pacific coast. S. virgatus is thought to reach its southern distributional limits just south of Hong Kong. In Hong Kong, mass mortalities of S. virgatus were recorded with the onset of the hot and wet season, with mussel cover decreasing at the upper limit of the mussel bed at Shek O from 82 % (~1746 ind m-2) in May to 9 % (~ 38 ind m-2) in August 2012. Elevated temperatures played an important role in driving physiological responses of the mussel, including heart rate, oxygen consumption and mantle water and haemolymph osmotic concentrations. The upper thermal limit in water (36 °C, as indicated by the Arrhenius breakpoint temperature, ABT), was unlikely to be reached by local seawater, but the ABT in air (~ 41 °C) was often lower than rock temperatures on Hong Kong shores, suggesting S. virgatus is living at its thermal limit. When immersed, both heart rates and oxygen consumption increased from 25 – 35 °C and dropped beyond 35 °C; whilst in air, haemolymph and mantle water osmolalities increased with duration (0 vs 6 hrs) and temperature (30 vs 40 °C) and 60 % of individuals died at 40 °C after 6 hours. Mortality of S. virgatus is, therefore, linked to the high temperatures and desiccation stress experienced on the shore, which are likely to impose high energetic costs. To better understand the performance of S. virgatus under natural conditions, and the energetic implications of thermal stress on its survival and fitness and hence potential distribution, a Dynamic Energy Budget (DEB) model was constructed. The model had a high goodness of fit. Mussels were predicted to live 5 years, and their main growth and energy reserves were derived from high assimilation during the hot and wet season when food was most abundant, while another slower growth period and reproduction occurred during the cool and dry season. Energy stored in the reserve during growth periods was likely to be allocated to combat thermal stress during the hot and wet season and reproduction during the cool and dry season. The DEB model was used to investigate the energy allocation strategies of S. virgatus under the most conservative and extreme scenarios associated with climate change as projected by the IPCC. The model predicted that reproductive events throughout the mussels’ life-span would be reduced by 30 – 70 %, despite an increase (18 – 470 %) in number of eggs per event. This reduction in the number of reproductive events might not be able to sustain local populations due to the high annual mortality. Such a decrease in performance and fitness, associated with not being able to reach the energy threshold necessary for somatic maintenance, suggests that S. virgatus may be limited to living lower on the shore, where conditions and duration of exposure are more benign, and ultimately experience a northwards range shift as environmental temperatures increase.published_or_final_version
Biological Sciences
Master
Master of Philosophy
32
Brits, Gert Johannes. "Ecophysiology of Leucospermum R. Br. seed germination in fynbos." Thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/26071.
Full text
33
Cooney, Sean Kevin. "The ecophysiology of the fish associated dinoflagellate (Crepidoodinium cyprinodontum)." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8453.
Full textAbstract:
Thesis (M.S.) -- University of Maryland, College Park, 2008.Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
34
Soares, Anna-Maria. "Ecophysiology of strains A and C of Potamophyrgus jenkinsi." Thesis, Bangor University, 1992. https://research.bangor.ac.uk/portal/en/theses/ecophysiology-of-strains-a-and-c-of-potamophyrgus-jenkinsi(249e52c0-076c-4c37-8ad8-41fd8e1fa099).html.
Full textAbstract:
The life history parameters growth, survivorship and fecundity were investigated in strains A and C of the clonal apomictic snail Potamopyrgus jenkinsi. Both strains were obtained from separate habitats. Strain A from an inland freshwater stream and strain C from a boating pond which receives seawater and is drained every winter. When reared from birth in constant laboratory conditions the two strains were shown to differ in life history strategy. Strain C showed rapid growth, matured early and at a relatively small size. Hence it had greater reproductive effort. Strain A delayed growth, matured relatively late in its life history and hence at a larger size. The results in this work suggests that strain A and C are distinct clones, which support recent electrophoretic studies. In manipulated environments of food stress and increased salinity the two strains continued to show significant differences. Both strains were plastic in their growth, reducing growth in response to decreasing food availability and high salinities. However at 5% and 10%SW the two strains showed an increase in growth from that of the control. Their reproductive output also decreased with decreasing food supply and increasing salinity. However, strain A was more sensitive to food and salinity stress, ceasing to release young at low ration and starved environments and at salinities of 20%SW and above. Strain C continued to release young in all environments, albeit at a reduced rate and at a cost to survivorship. A yearlong field study on the size-frequency distribution of the two strains in their natural habitat showed the life history of strain A to approximate `IC'-selection and strain C to approximate `e-selection.
35
Steyn, Paul-Pierre. "The ecophysiology of Gelidium Pristoides (Turner) Kuetzing : towards commercial cultivation." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1117.
Full textAbstract:
The ecophysiology of the red alga Gelidium pristoides (Turner) Kuetzing was investigated in an effort to establish a technique for commercial cultivation. The seaweed is of commercial importance in South Africa where it is harvested from the intertidal zone rocky shores along the coast. It is dried and exported abroad for the extraction of agar. Yields and quality could be improved by cultivation in commercial systems. However, attempts at growing the seaweed in experimental systems have all ended in failure. This study aimed to describe the conditions in which the seaweed grows naturally; and investigate its physiological response to selected physical conditions in the laboratory in order to determine suitable conditions for mariculture. Ecological studies showed that G. pristoides grew above the spring low tide water level. The upper limit of the seaweed’s vertical distribution range, as well as its abundance, was largely dependent on wave exposure. The zone normally inhabited by G. pristoides was dominated by coralline turf in sheltered areas, while the abundance of G. pristoides increased towards more exposed rocky shore sites. The seaweed occurred among species such as Pattelid limpets and barnacles, but was usually the dominant macroalga in this zone, with coralline turf and encrusting algae being the only others. Physical conditions in the part of the intertidal zone inhabited by G. pristoides were highly variable. During low tide temperatures could vary by as much as 10°C within the three hours between tidal inundation of the seaweed population, while salinity varied by up to 9 ppt, and light intensity by as much as 800 μmol m-2 s-1. During these exposure periods the seaweed suffered up to 20% moisture loss. Laboratory experiments on the seaweed’s response to these conditions indicated that it was well adapted to such fluctuations. It had a broad salinity (20 and 40 ppt), and temperature tolerance range (18 to 24°C), with an o ptimum of temperature of 21°C for photosynthesis, while there was no difference in the photosynthetic rate of the alga within the 20 to 40 ppt salinity range. The alga had a low saturating irradiance (ca. 45 – 80 μmol m-2 s-1) equipping it well for photosynthesis in turbulent environments, with high light attenuation, but poorly to unattenuated light conditions. Exposure resulted in an initial increase in photosynthetic rate followed by a gradual decrease thereafter. pH drift experiments showed that low seawater pH, and associated increased carbon dioxide availability, resulted in an increase in photosynthetic rate. This response suggests that the seaweed has a high affinity for carbon dioxide, while the reduction in photosynthetic rate in response to bicarbonate use inhibition indicates that it also has the capacity for bicarbonate use. The high affinity of Gelidium pristoides for carbon dioxide as an inorganic carbon source appears to be the primary reason for the low abundance of the alga on sheltered rocky shore areas, and also explains the failure of the alga to grow in tank or open-water mariculture systems. Exposed rocky shores have experience heavy wave action, and the resultant aeration and mixing of nearshore waters increases the availability of carbon dioxide, which is considered a limiting resource. The absence of such mixing and aeration at sheltered site makes this less suitable habitat for G. pristoides. Periodic exposure also makes high levels of atmospheric carbon dioxide available from which the seaweed benefits. The traditional mariculture systems in which attempts have been made to cultivate the seaweed failed to satisfy either of the above conditions.
36
Dodds, Lyndsey A. "The ecophysiology of the cold-water coral Lophelia pertusa (Scleractinia)." Thesis, University of the Highlands and Islands, 2007. https://pure.uhi.ac.uk/portal/en/studentthesis/the-ecophysiology-of-the-coldwater-coral-lophelia-pertusa-scleractinia(2ed27e7e-1011-4162-bdc1-a06321a69364).html.
Full textAbstract:
Lophelia pertusa is the world’s most common and widespread framework-forming cold-water coral. It forms deep-water coral reefs and carbonate mounts supporting diverse animal communities on the continental shelf and on seamounts. Cold-water corals are found throughout most of the world’s oceans at depths of around 200 to 1000 meters. Unlike their tropical counterparts, cold-water corals do not contain symbiotic algae. These recently discovered ecosystems have been damaged by deep-sea fishing and are threatened by climate change. Despite this, very little is known about the ecophysiology of L. pertusa and its likely response to environmental changes. The aims of this research were to investigate the physiology of L. pertusa and relate this to its environment. In particular, this research focused on the respiratory physiology, growth and lipid signature of L. pertusa. This is the first study to investigate the physiology of L. pertusa and relate it to aspects of its natural environment, including temperature and oxygen availability. Results suggest that L. pertusa has slow physiological rates that vary geographically and may be dependent on food sources. Lipid analysis suggested a strong link to surface production and preferential feeding on copepods. It appears that L. pertusa is sensitive to small temperature changes and is at least partially limited in distribution by oxygen levels. This environment is likely to be threatened by changes in seawater temperature, ocean acidification, alteration of food webs and water masses as well as destructive fishing impacts. The results of this research provide vital information that will underpin future research and allow us to predict the effects of anthropogenic impacts on L. pertusa.
37
McMaster, Kellie Anne. "Ecophysiology of Australian cocooning and non-cocooning, burrowing, desert frogs." University of Western Australia. School of Animal Biology, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0138.
Full textAbstract:
[Truncated abstract] This thesis explores the ecophysiology of cocooning and non-cocooning Australian burrowing desert frogs in order to specify the details of these two alternative survival strategies. Many details of these life-history strategies have not previously been determined for Australian frogs. In this study the detailed method of function and formation of the cocoon itself was investigated for the first time, as were the moulting cycles, which drive cocoon formation. Cocooning species had consistently shorter inter-moult-periods than non-cocooning species, which is presumably adaptive, allowing production of cocoon layers at a faster rate. Transmission electron microscopy revealed cocoon formation in Cyclorana platycephala to be a plastic, rather than static adaptation. The initial stages of cocoon formation appear to be the most critical. Cocoon layer formation is fastest in the first month and the initial layers produced are thicker than subsequent layers. Also, only in this initial stage does layer thickness appear to be influenced by soil moisture. Scanning electron microscopy confirmed the lips, eyelids and cloaca of cocooned frogs to be sealed by continuous layers of cocoon. However, it remains unclear precisely how the continuous junctions between cells from discreet sources, such as the upper and lower lip, are formed. Measurements of evaporative water loss and resistance over various relative humidity gradients suggested that water content within the cocoon structure is very low unless the external RH is > 93%. Therefore, anuran cocoon is confirmed to function as a specialised and highly effective barrier to water diffusion in arid-zone frogs. ... Within a dune swale, N. aquilonius burrows were an average depth of 1.13 m in loamy sand (clay = 6%, silt = 7%). Neobatrachus aquilonius excavated from the claypan had well formed cocoons, while those found in the dune swale had only one or two thin layers, indicating cocoon formation had only just commenced, although the last rainfall had been over six months prior. This suggests that N. aquilonius is able to switch between the cocooning and non-cocooning strategy in different soil types and different conditions. In summary, cocoon formation was found not to be an entirely passive accumulation of layers. Cocoon formation involved specialisation in the rate and thickness of epithelial layer production and the sealing of layers over lips, eyes and cloaca. Moreover, the cocoon was confirmed to operate effectively as a diffusion barrier at all except the highest external relative humidity. Like cocoon-forming species, Notaden nichollsi was found to metabolically depress to survive for longer periods underground. However, they cannot survive for the entire period
38
au, jcos@iinet net, and Jeffrey John Cosgrove. "Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence." Murdoch University, 2007. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20071129.122222.
Full textAbstract:
Marine phytoplankton ecophysiological state and primary production measurements have typically been controversial due to potential impacts of measurement techniques. Advances in chl-a fluorescence techniques have provided a means for rapid, non-invasive measurement of electron transport through photosystem 2 (PSII) in dilute phytoplankton suspensions. While studies on higher plants have outlined a close relationship between PSII electron transport and carbon fixation, results from studies on microalgae reveal significant variations in the relationship.
Three species of phytoplankton representing three major taxonomic groups of the marine phytoplankton were used in this study: (1) Chaetoceros muelleri CS176 Lemmermann (Bacillariophyta), (2) Isochrysis galbana CS177 Parke (Haptophyta) and, (3) Nannochloropsis oculata CS179 (Droop) Hibberd (Ochrophyta, eustigmatophyte). Each species was cultured in semicontinuous culture and primary
production was estimated using oxygen evolution and carbon fixation techniques and compared against predictions based on chl-a fluorescence measurements. It was found that predicted values of primary production both under-estimated and overestimated actual carbon fixation measured via radioisotope (14C) techniques. This variation was primarily explained by probable errors in the assumed values for PSII density. The relationship between oxygen evolution or carbon fixation with chl-a fluorescence-derived measures was commonly linear below the light saturation parameter, with a departure from linearity occurring at higher irradiances. This departure from linearity was greatest in cultures adapted to low light conditions. At higher light intensities alternative electron pathways such as the Mehler reaction and/or chlororespiration are likely to be more active in low light-adapted cultures, leading to this greater non-linearity.
Chl-a fluorescence measurements were also found to be a useful in characterising ecophysiology using photosynthesis-versus irradiance curves. However, an important caveat on this is the measurement of PSII density (çPSII) rather than use of an assumed value as changes in çPSII can have a profound impact on light curve parameters.
A field study in Fremantle Harbour found a healthy (negligible nutrient starvation), diatom dominated, phytoplankton community. Results suggest that phytoplankton are able to begin boosting photosynthetic capability just prior to morning twilight. Waters in the harbour were well mixed via tidal motion and substantial midday photoinhibition was not observed. Data suggest levels of primary production at the mouth of the harbour are similar to those of coastal waters in the plume of the Ocean Reef wastewater outfall.
39
Dadkhah, Ali Reza. "Ecophysiology of sugar beet (Beta vulgaris L.) under salt stress." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246614.
Full text
40
Dominguez-Bello, Maria Gloria. "Microbial ecophysiology in the rumen of sheep fed tropical forages." Thesis, University of Aberdeen, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257608.
Full textAbstract:
In Venezuela, four sheep fitted with rumen cannulas were fed the toxin-containing legumes Leucaena leucocephala (sun dried leaves and stems) and Canavalia ensiformis (grains). L. leucocephala did not have any apparent toxic effects on the animals, in spite of the presence of the toxic compounds 3,4 DHP and 2,3 DHP in the rumen. There were no significant effects on the rumen pH, concentrations of VFAs, microbial counts, rate of rice straw degradation or in the rumen outflow of liquids and solids. However, there was an increase in the concentration of ammonia in the rumen, and in the number of Gram negative rods isolated from the rumen of sheep when L. leucocephala was added to the diet. When C. ensiformis was supplemented the presence of canavanine in the rumen was confirmed. Sheep did not show signs of toxicity. There was no effect on rumen pH, microbial counts, degradation of rice straw or rates of outflow of liquids and solids from the rumen. There was a decrease in the rumen concentrations of valerate and ammonia and an increase in the numbers of Gram negative bacteria isolated from the rumen of sheep as the dietary inclusion of Canavalia increased. Several pure cultures capable of mimosine, 2,4 DHP and (in fewer cases) 3,4 DHP wre isolated. One of them, a Gram variable spore-forming rod, presumably a new species of Clostridium, was characterised. The presence of degraders of mimosine and DHP in the rumen presumably accounted for the lack of toxicity of L. leucocephala in Venezuela. The effect of canavanine on the growth and products of fermentation of pure cultures was independent of the Gram staining reaction and the results of experiments using media containing either peptides and amino acids or free amino acids alone suggest that canavanine may have an effect on peptide hydrolysis.
41
McMaster, Kellie Anne. "Ecophysiology of Australian cocooning and non-cocooning, burrowing, desert frogs /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0138.
Full text
42
Thessen, Anne E. "Taxonomy and ecophysiology of (Pseudo-nitzschia) in the Chesapeake Bay." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7707.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
43
Altshuler, Douglas Leonard. "Ecophysiology of hummingbird flight along elevational gradients an integrated approach /." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035932.
Full text
44
Kawamata, Yoshiyuki R. "Environmental effects on the ecophysiology and morphology of Acacia species /." [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16328.pdf.
Full text
45
Kachenko, Anthony. "Ecophysiology and phytoremediation potential of heavy metal(Loid) accumulating plants." Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/6348.
Full textAbstract:
Soil contamination with heavy metal(loid)s is a major environmental problem that requires effective and affordable remediation technologies. The utilisation of plants to remediate heavy metal(loid)s contaminated soils has attracted considerable interest as a low cost green remediation technology. The process is referred to as phytoremediation, and this versatile technology utilises plants to phytostabilise and/or phytoextract heavy metal(loid)s from contaminated soils, thereby effectively minimising their threat to ecosystem, human and animal health. Plants that can accumulate exceptionally high concentrations of heavy metal(loid)s into above-ground biomass are referred to as hyperaccumulators, and may be exploited in phytoremediation, geobotanical prospecting and/or phytomining of low-grade ore bodies. Despite the apparent tangible benefits of utilising phytoremediation techniques, a greater understanding is required to comprehend the ecophysiological aspects of species suitable for phytoremediation purposes. A screening study was instigated to assess phytoremediation potential of several fern species for soils contaminated with cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn). Hyperaccumulation was not observed in any of the studied species, and in general, species excluded heavy metal uptake by restricting their translocation into aboveground biomass. Nephrolepis cordifolia and Hypolepis muelleri were identified as possible candidates in phytostabilisation of Cu-, Pb-, Ni- or Zn-contaminated soils and Dennstaedtia davallioides appeared favourable for use in phytostabilisation of Cu- and Zn-contaminated soils. Conversely, Blechnum nudum, B. cartilagineum, Doodia aspera and Calochlaena dubia were least tolerant to most heavy metals and were classified as being least suitable for phytoremediation purposes Ensuing studies addressed the physiology of arsenic (As) hyperaccumulation in a lesser known hyperaccumulator, Pityrogramma calomelanos var. austroamericana. The phytoremediation potential of this species was compared with that of the well known As hyperaccumulator Pteris vittata. Arsenic concentration of 3,008 mg kg–1 dry weight (DW) occurred in P. calomelanos var. austroamericana fronds when exposed to 50 mg kg–1 As without visual symptoms of phytotoxicities. Conversely, P. vittata was able to hyperaccumulate 10,753 mg As kg–1 DW when exposed to 100 mg kg–1 As without the onset of phytotoxicities. In P. calomelanos var. austroamericana, As was readily translocated to fronds with concentrations 75 times greater in fronds than in roots. This species has the potential for use in phytoremediation of soils with As levels up to 50 mg kg–1. Localisation and spatial distribution of As in P. calomelanos var. austroamericana pinnule and stipe tissues was investigated using micro-proton induced X-ray emission spectrometry (µ-PIXE). Freeze-drying and freeze-substitution protocols (using tetrahydrofuran [THF] as a freeze-substitution medium) were compared to ascertain their usefulness in tissue preservation. Micro-PIXE results indicated that pinnule sections prepared by freeze-drying adequately preserved the spatial elemental distribution and tissue structure of pinnule samples. In pinnules, µ-PIXE results indicated higher As concentration than in stipe tissues, with concentrations of 3,700 and 1,600 mg As kg–1 DW, respectively. In pinnules, a clear pattern of cellular localisation was not resolved whereas vascular bundles in stipe tissues contained the highest As concentration (2,000 mg As kg–1 DW). Building on these µ-PIXE results, the chemical speciation of As in P. calomelanos var. austroamericana was determined using micro-focused X-ray fluorescence (µ-XRF) spectroscopy in conjunction with micro-focused X-ray absorption near edge structure (µ-XANES) spectroscopy. The results suggested that arsenate (AsV) absorbed by roots was reduced to arsenite (AsIII) in roots prior to transport through vascular tissues as AsV and AsIII. In pinnules, AsIII was the predominant species, presumably as aqueous-oxygen coordinated compounds. Linear least-squares combination fits of µ-XANES spectra showed AsIII as the predominant component in all tissues sampled. The results also revealed that sulphur containing thiolates may, in part sequester accumulated As. The final aspect of this thesis examined several ecophysiological strategies of Ni hyperaccumulation in Hybanthus floribundus subsp. floribundus, a native Australian perennial shrub species and promising candidate in phytoremediation of Ni-contaminated soils. Micro-PIXE analysis revealed that cellular structure in leaf tissues prepared by freeze-drying was adequately preserved as compared to THF freeze-substituted tissues. Elemental distribution maps of leaves showed that Ni was preferentially localised in the adaxial epidermal tissues and leaf margin, with concentration of 10,000 kg–1 DW in both regions. Nickel concentrations in stem tissues obtained by µ-PIXE analysis were lower than in the leaf tissues (1,800 mg kg–1 vs. 7,800 mg kg–1 DW, respectively), and there was no clear pattern of compartmentalisation across different anatomical regions. It is possible that storage of accumulated Ni in epidermal tissues may provide Ni tolerance to this species, and may further act as a deterrent against herbivory and pathogenic attack. In H. floribundus subsp. floribundus seeds, µ-PIXE analysis did not resolve a clear pattern of Ni compartmentalisation and suggests that Ni was able to move apoplastically within the seed tissues. The role of organic acids and free amino acids (low molecular weight ligands [LMW]) in Ni detoxification in H. floribundus subsp. floribundus were quantified using high performance liquid chromatography (HPLC) and ultra performance liquid chromatography (UPLC). Nickel accumulation stimulated a significant increase in citric acid concentration in leaf extracts, and based on the molar ratios of Ni to citric acid (1.3:1–1.7:1), citric acid was sufficient to account for approximately 50% of the accumulated Ni. Glutamine, alanine and aspartic acid concentrations were also stimulated in response to Ni hyperaccumulation and accounted for up to 75% of the total free amino acid concentration in leaf extracts. Together, these LMW ligands may complex with accumulated Ni and contribute to its detoxification and storage in this hyperaccumulator species. Lastly, the hypothesis that hyperaccumulation of Ni in certain plants may act as an osmoticum under water stress (drought) was tested in context of H. floribundus subsp. floribundus. A 38% decline in water potential and a 68% decline in osmotic potential occurred between water stressed and unstressed plants, however, this was not matched by an increase in accumulated Ni. The results suggested that Ni was unlikely to play a role in osmotic adjustment in this species. Drought stressed plants exhibited a low water use efficiency which might be a conservative ecophysiological strategy enabling survival of this species in competitive water-limited environments.
46
Kachenko, Anthony. "Ecophysiology and phytoremediation potential of heavy metal(Loid) accumulating plants." University of Sydney, 2008. http://hdl.handle.net/2123/6348.
Full textAbstract:
Doctor of Philosophy(PhD)Soil contamination with heavy metal(loid)s is a major environmental problem that requires effective and affordable remediation technologies. The utilisation of plants to remediate heavy metal(loid)s contaminated soils has attracted considerable interest as a low cost green remediation technology. The process is referred to as phytoremediation, and this versatile technology utilises plants to phytostabilise and/or phytoextract heavy metal(loid)s from contaminated soils, thereby effectively minimising their threat to ecosystem, human and animal health. Plants that can accumulate exceptionally high concentrations of heavy metal(loid)s into above-ground biomass are referred to as hyperaccumulators, and may be exploited in phytoremediation, geobotanical prospecting and/or phytomining of low-grade ore bodies. Despite the apparent tangible benefits of utilising phytoremediation techniques, a greater understanding is required to comprehend the ecophysiological aspects of species suitable for phytoremediation purposes. A screening study was instigated to assess phytoremediation potential of several fern species for soils contaminated with cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn). Hyperaccumulation was not observed in any of the studied species, and in general, species excluded heavy metal uptake by restricting their translocation into aboveground biomass. Nephrolepis cordifolia and Hypolepis muelleri were identified as possible candidates in phytostabilisation of Cu-, Pb-, Ni- or Zn-contaminated soils and Dennstaedtia davallioides appeared favourable for use in phytostabilisation of Cu- and Zn-contaminated soils. Conversely, Blechnum nudum, B. cartilagineum, Doodia aspera and Calochlaena dubia were least tolerant to most heavy metals and were classified as being least suitable for phytoremediation purposes Ensuing studies addressed the physiology of arsenic (As) hyperaccumulation in a lesser known hyperaccumulator, Pityrogramma calomelanos var. austroamericana. The phytoremediation potential of this species was compared with that of the well known As hyperaccumulator Pteris vittata. Arsenic concentration of 3,008 mg kg–1 dry weight (DW) occurred in P. calomelanos var. austroamericana fronds when exposed to 50 mg kg–1 As without visual symptoms of phytotoxicities. Conversely, P. vittata was able to hyperaccumulate 10,753 mg As kg–1 DW when exposed to 100 mg kg–1 As without the onset of phytotoxicities. In P. calomelanos var. austroamericana, As was readily translocated to fronds with concentrations 75 times greater in fronds than in roots. This species has the potential for use in phytoremediation of soils with As levels up to 50 mg kg–1. Localisation and spatial distribution of As in P. calomelanos var. austroamericana pinnule and stipe tissues was investigated using micro-proton induced X-ray emission spectrometry (µ-PIXE). Freeze-drying and freeze-substitution protocols (using tetrahydrofuran [THF] as a freeze-substitution medium) were compared to ascertain their usefulness in tissue preservation. Micro-PIXE results indicated that pinnule sections prepared by freeze-drying adequately preserved the spatial elemental distribution and tissue structure of pinnule samples. In pinnules, µ-PIXE results indicated higher As concentration than in stipe tissues, with concentrations of 3,700 and 1,600 mg As kg–1 DW, respectively. In pinnules, a clear pattern of cellular localisation was not resolved whereas vascular bundles in stipe tissues contained the highest As concentration (2,000 mg As kg–1 DW). Building on these µ-PIXE results, the chemical speciation of As in P. calomelanos var. austroamericana was determined using micro-focused X-ray fluorescence (µ-XRF) spectroscopy in conjunction with micro-focused X-ray absorption near edge structure (µ-XANES) spectroscopy. The results suggested that arsenate (AsV) absorbed by roots was reduced to arsenite (AsIII) in roots prior to transport through vascular tissues as AsV and AsIII. In pinnules, AsIII was the predominant species, presumably as aqueous-oxygen coordinated compounds. Linear least-squares combination fits of µ-XANES spectra showed AsIII as the predominant component in all tissues sampled. The results also revealed that sulphur containing thiolates may, in part sequester accumulated As. The final aspect of this thesis examined several ecophysiological strategies of Ni hyperaccumulation in Hybanthus floribundus subsp. floribundus, a native Australian perennial shrub species and promising candidate in phytoremediation of Ni-contaminated soils. Micro-PIXE analysis revealed that cellular structure in leaf tissues prepared by freeze-drying was adequately preserved as compared to THF freeze-substituted tissues. Elemental distribution maps of leaves showed that Ni was preferentially localised in the adaxial epidermal tissues and leaf margin, with concentration of 10,000 kg–1 DW in both regions. Nickel concentrations in stem tissues obtained by µ-PIXE analysis were lower than in the leaf tissues (1,800 mg kg–1 vs. 7,800 mg kg–1 DW, respectively), and there was no clear pattern of compartmentalisation across different anatomical regions. It is possible that storage of accumulated Ni in epidermal tissues may provide Ni tolerance to this species, and may further act as a deterrent against herbivory and pathogenic attack. In H. floribundus subsp. floribundus seeds, µ-PIXE analysis did not resolve a clear pattern of Ni compartmentalisation and suggests that Ni was able to move apoplastically within the seed tissues. The role of organic acids and free amino acids (low molecular weight ligands [LMW]) in Ni detoxification in H. floribundus subsp. floribundus were quantified using high performance liquid chromatography (HPLC) and ultra performance liquid chromatography (UPLC). Nickel accumulation stimulated a significant increase in citric acid concentration in leaf extracts, and based on the molar ratios of Ni to citric acid (1.3:1–1.7:1), citric acid was sufficient to account for approximately 50% of the accumulated Ni. Glutamine, alanine and aspartic acid concentrations were also stimulated in response to Ni hyperaccumulation and accounted for up to 75% of the total free amino acid concentration in leaf extracts. Together, these LMW ligands may complex with accumulated Ni and contribute to its detoxification and storage in this hyperaccumulator species. Lastly, the hypothesis that hyperaccumulation of Ni in certain plants may act as an osmoticum under water stress (drought) was tested in context of H. floribundus subsp. floribundus. A 38% decline in water potential and a 68% decline in osmotic potential occurred between water stressed and unstressed plants, however, this was not matched by an increase in accumulated Ni. The results suggested that Ni was unlikely to play a role in osmotic adjustment in this species. Drought stressed plants exhibited a low water use efficiency which might be a conservative ecophysiological strategy enabling survival of this species in competitive water-limited environments.
47
Cosgrove, Jeffrey John. "Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence." Thesis, Cosgrove, Jeffrey John (2007) Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence. PhD thesis, Murdoch University, 2007. https://researchrepository.murdoch.edu.au/id/eprint/503/.
Full textAbstract:
Marine phytoplankton ecophysiological state and primary production measurements have typically been controversial due to potential impacts of measurement techniques. Advances in chl-a fluorescence techniques have provided a means for rapid, non-invasive measurement of electron transport through photosystem 2 (PSII) in dilute phytoplankton suspensions. While studies on higher plants have outlined a close relationship between PSII electron transport and carbon fixation, results from studies on microalgae reveal significant variations in the relationship.
Three species of phytoplankton representing three major taxonomic groups of the marine phytoplankton were used in this study: (1) Chaetoceros muelleri CS176 Lemmermann (Bacillariophyta), (2) Isochrysis galbana CS177 Parke (Haptophyta) and, (3) Nannochloropsis oculata CS179 (Droop) Hibberd (Ochrophyta, eustigmatophyte). Each species was cultured in semicontinuous culture and primary production was estimated using oxygen evolution and carbon fixation techniques and compared against predictions based on chl-a fluorescence measurements. It was found that predicted values of primary production both under-estimated and overestimated actual carbon fixation measured via radioisotope (14C) techniques. This variation was primarily explained by probable errors in the assumed values for PSII density. The relationship between oxygen evolution or carbon fixation with chl-a fluorescence-derived measures was commonly linear below the light saturation parameter, with a departure from linearity occurring at higher irradiances. This departure from linearity was greatest in cultures adapted to low light conditions. At higher light intensities alternative electron pathways such as the Mehler reaction and/or chlororespiration are likely to be more active in low light-adapted cultures, leading to this greater non-linearity.
Chl-a fluorescence measurements were also found to be a useful in characterising ecophysiology using photosynthesis-versus irradiance curves. However, an important caveat on this is the measurement of PSII density ([eta]PSII) rather than use of an assumed value as changes in [eta]PSII can have a profound impact on light curve parameters.
A field study in Fremantle Harbour found a healthy (negligible nutrient starvation), diatom dominated, phytoplankton community. Results suggest that phytoplankton are able to begin boosting photosynthetic capability just prior to morning twilight. Waters in the harbour were well mixed via tidal motion and substantial midday photoinhibition was not observed. Data suggest levels of primary production at the mouth of the harbour are similar to those of coastal waters in the plume of the Ocean Reef wastewater outfall.
48
Cosgrove, Jeffrey John. "Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence." Cosgrove, Jeffrey John (2007) Marine phytoplankton primary production and ecophysiology using chlorophyll-A fluorescence. PhD thesis, Murdoch University, 2007. http://researchrepository.murdoch.edu.au/503/.
Full textAbstract:
Marine phytoplankton ecophysiological state and primary production measurements have typically been controversial due to potential impacts of measurement techniques. Advances in chl-a fluorescence techniques have provided a means for rapid, non-invasive measurement of electron transport through photosystem 2 (PSII) in dilute phytoplankton suspensions. While studies on higher plants have outlined a close relationship between PSII electron transport and carbon fixation, results from studies on microalgae reveal significant variations in the relationship.
Three species of phytoplankton representing three major taxonomic groups of the marine phytoplankton were used in this study: (1) Chaetoceros muelleri CS176 Lemmermann (Bacillariophyta), (2) Isochrysis galbana CS177 Parke (Haptophyta) and, (3) Nannochloropsis oculata CS179 (Droop) Hibberd (Ochrophyta, eustigmatophyte). Each species was cultured in semicontinuous culture and primary production was estimated using oxygen evolution and carbon fixation techniques and compared against predictions based on chl-a fluorescence measurements. It was found that predicted values of primary production both under-estimated and overestimated actual carbon fixation measured via radioisotope (14C) techniques. This variation was primarily explained by probable errors in the assumed values for PSII density. The relationship between oxygen evolution or carbon fixation with chl-a fluorescence-derived measures was commonly linear below the light saturation parameter, with a departure from linearity occurring at higher irradiances. This departure from linearity was greatest in cultures adapted to low light conditions. At higher light intensities alternative electron pathways such as the Mehler reaction and/or chlororespiration are likely to be more active in low light-adapted cultures, leading to this greater non-linearity.
Chl-a fluorescence measurements were also found to be a useful in characterising ecophysiology using photosynthesis-versus irradiance curves. However, an important caveat on this is the measurement of PSII density ([eta]PSII) rather than use of an assumed value as changes in [eta]PSII can have a profound impact on light curve parameters.
A field study in Fremantle Harbour found a healthy (negligible nutrient starvation), diatom dominated, phytoplankton community. Results suggest that phytoplankton are able to begin boosting photosynthetic capability just prior to morning twilight. Waters in the harbour were well mixed via tidal motion and substantial midday photoinhibition was not observed. Data suggest levels of primary production at the mouth of the harbour are similar to those of coastal waters in the plume of the Ocean Reef wastewater outfall.
49
Headley, A. D. "The comparative autecology of some European species of Lycopodium sensu lato." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376575.
Full text
50
Friend, Andrew David. "Investigations on the physiological basis of adaptation to altitude in Nardus stricta L." Thesis, University of Cambridge, 1989. https://www.repository.cam.ac.uk/handle/1810/270408.
Full text