Dissertations / Theses on the topic 'Sulfur dioxide – Physiological effect'

The X-band EPR spectrometry system was modified to allow for the in situ monitoring of free radical changes in attached, intact plant leaves, which were caused by stress factors such as exposure to excessive photon flux density, ozone or sulphur dioxide. This was done through use of the dewar insert of the variable temperature accessory as a guide, the construction of 'T' shaped cellulose acetate holders to which leaves could be attached with adhesive tape, and modification of the gas flow system used for controlled temperature studies. Kinetic studies of free radical formation were possible with leaves which had minimal underlying Fe⁺⁺ and Mn⁺⁺ signals. In leaves with large underlying signals a Varian software program was used to subtract overlapping signals from each other, thereby revealing the free-radical signal changes which occurred under different light regimes and stress conditions. Preliminary investigation disclosed the formation of a new signal upon prolonged exposure to far-red light and the effect of oxygen depletion upon photosynthetic Signals I and II. Leaves subject to high photon flux density reveal an unreported free-radical signal, which decays upon exposure to microwave radiation; and concomitant damage to Photosystems I and II. Upon elimination of this signal leaves return to the undamaged state or reveal permanent damage to either photo-system, depending upon the degree of damage. Kentucky bluegrass and perennial ryegrass leaves subject to low levels of ozone (up to 80ppb) for periods of 8 hours show no changes in free-radical signal formation. At intermediate levels of ozone (80-250ppb) a new free-radical signal was formed within 3 hours of fumigation, Signal II was decreased and Signal I decayed. These changes were reversible if fumigation was terminated. At fumigation levels exceeding 250ppb a different new irreversible free-radical signal was formed in darkness within 1.5 hours of fumigation. Radish, Kentucky bluegrass and perennial ryegrass leaves subject to high levels of sulphur dioxide (10-500ppm) reveal the formation of Signal I upon irradiation with broad-band white or 650nm light, thereby indicating an interruption of normal electron flow from PSII to PSI. Damage to the oxygen-evolving complex and reaction centre of PSII is also revealed through changes in Signal II and the Mn⁺⁺ signal. These changes in the normal EPR signals are dose-dependent. Leaves subject to low levels of sulphur dioxide (600-2000ppb) reveal the disappearance of Signal I after 3 hours of fumigation and the formation of a new free-radical signal with parameters similar to the sulphur trioxide free-radical signal. These latter changes are partially reversible upon termination of fumigation. After prolonged exposure to either ozone or sulphur dioxid a free-radical signal with parameters similar to the superoxid anion free-radical signal is formed in plant leaves.<br>Land and Food Systems, Faculty of<br>Graduate

This study examined the relationship between expired non-metabolic CO₂ (EX CO₂) and the accumulation of blood lactate, while emphasis was placed on the ventilatory (EX CO₂ and VE/VO₂) and lactate threshold relationship. Twenty-one elite cyclists (15 males, 6 females) performed a progressive intensity bicycle ergometer test (PIT) during which ventilatory parameters were monitored on-line at 15 second intervals, and blood lactate sampling occured on each minute. Threshold values were determined for each of the three indices; excess CO₂ (EXTT), VE/V0₂ (VVTT), and blood lactate (LATT). The three threshold values (EXTT, VVTT, LATT) all correlated significantly (P<0.001) when each was expressed as an absolute VO₂ (1/min). A significant RM ANOVA (F=8.41, P<0. 001) and post hoc correlated t-tests demonstrated significant differences between the EIXTT and LATT (P<0.001) and the EXTT and VVTT values (P<0.025). The LATT occured at an average blood lactate concentration of 3.35 mmol/1, while the mean expired excess CO₂ volume at the EXTT was 14.04 ml/kg/min. Over an 11 minute range across the threshold values (EXTT and LATT), which were used as relative points of reference, the expired EXC02 volume (ml/kg/min) and blood lactate concentration (mmol/1) correlated significantly (r=0. 69, P<0. 001). Higher individual correlations over the same period of time <r=0.82 - 0.96, P <0.001) stress the individual nature of this relationship. Expired EXCO₂ volume appeared to track blood lactate levels over this 11 minute period when the significant threshold difference (1.35 min.) was taken into consideration. These results indicate a strong relationship between the three threshold values, although changes and expired EXCO₂ precede changes in blood lactate concentration and the ventilatory equivelant (VE/VO₂). Although changes in expired EXCO₂ volume appear to track changes in blood lactate concentration, blood lactate concentration can not be accurately predicted from expired EXCO₂ volume as the nature of this relationship varies between individuals and. appears to be influenced by gender.<br>Education, Faculty of<br>Curriculum and Pedagogy (EDCP), Department of<br>Graduate

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.<br>Ph. D.

Thesis (MSc)--Stellenbosch University, 2000.<br>ENGLISH ABSTRACT: This investigation was undertaken to determine whether elevated concentrations of dissolved inorganic carbon (DIC) supplied to plant roots could improve plant growth and alleviate the effects of salinity stress on tomato plants infected with arbuscular mycorrhizae. Lycopersicon esculentum cv. FI44 seedlings were grown in hydroponic culture (pH 5.8) with 0 and 75 mM NaCI and with or without infection with the fungus Glomus mosseae. The root solution was aerated with ambient CO2 (360 ppm) or elevated CO2 ( 5 000 ppm) concentrations. The arbuscular and hypha I components of mycorrhizal infection as well as the percentages total infection were decreased or increased according to the variation in seasons. The plant dry weight of mycorrhizal plants was increased by 30% compared to non-mycorrhizal plants at elevated concentrations of CO2, while the dry weight was decreased by 68% at ambient CO2 concentrations. Elevated CO2 also stimulated the growth of the mycorrhizal fungus. Elevated CO2 increased the plant dry weight and stimulated fungal growth of mycorrhizal plants possibly by the provision of carbon due to the incorporation of HCO)- by PEPc. Plant roots supplied with elevated concentrations of CO2 had a decreased CO2 release rate compared to roots at ambient CO2. This decrease in CO2 release rate at elevated CO2 was due to the increased incorporation of HC03- by PEPc activity. Under conditions of salinity stress plants had a higher ratio of N03-: reduced N in the xylem sap compared to plants supplied with 0 mM NaCI. Under salinity stress conditions, more N03- was transported in the xylem stream possibly because of the production of more organic acids instead of amino acids due to low P conditions under which the plants were grown. The N03· uptake rate of plants increased at elevated concentrations of CO2 in the absence of salinity because the HCO)- could be used for the production of amino acids. In the presence of salinity, carbon was possibly used for the production of organic acids that diverted carbon away from the synthesis of amino acids. It was concluded that mycorrhizas were beneficial for plant growth under conditions of salinity stress provided that there was an additional source of carbon. Arbuscular mycorrhizal infection did not improve the nutrient uptake of hydroponically grown plants.<br>AFRIKAANSE OPSOMMING: In hierdie studie was die effek van verhoogde konsentrasies opgeloste anorganiese koolstof wat aan plant wortels verskaf is, getoets om te bepaal of dit die groei van plante kan verbeter asook of sout stres verlig kon word in tamatie plante wat met arbuskulêre mikorrhizas geïnfekteer was. Lycorpersicon esculentum cv. FJ44 saailinge was in water kultuur gegroei (pH 5.8) met 0 en 75 mM NaCI asook met of sonder infeksie met die fungus Glomus mosseae. Die plant wortels was bespuit met normale CO2 (360 dele per miljoen (dpm)) sowel as verhoogde CO2 (5 000 dpm) konsentrasies. Die arbuskulere en hife komponente, sowel as die persentasie infeksie was vermeerder of verminder na gelang van die verandering in seisoen. Die plant droë massa van mikorrhiza geïnfekteerde plante by verhoogde CO2 konsentrasies was verhoog met 30% in vergelyking met plante wat nie geïnfekteer was nie, terwyl die droë massa met 68% afgeneem het by gewone CO2 konsentrasies. Verhoogde CO2 konsentrasies het moontlik die plant droë massa en die groei van die fungus verbeter deur koolstof te verskaf as gevolg van die vaslegging van HCO)- deur die werking van PEP karboksilase. Plant wortels wat met verhoogde CO2 konsentrasies bespuit was, het 'n verlaagde CO2 vrystelling getoon in vergelyking met die wortels by normale CO2 vlakke. Die vermindering in CO2 vrystelling van wortels by verhoogde CO2 was die gevolg van die vaslegging van HC03- deur PEPk aktiwiteit. Onder toestande van sout stres, het plante 'n groter hoeveelheid N03- gereduseerde N in die xileemsap bevat in vergelyking met plante wat onder geen sout stres was nie, asook meer NO)- was in die xileemsap vervoer moontlik omdat meer organiese sure geproduseer was ten koste van amino sure. Dit was die moontlike gevolg omdat die plante onder lae P toestande gegroei het. Die tempo van NO.; opname was verhoog onder verhoogde CO2 konsentrasies en in die afwesigheid van sout stres omdat die HCO)- vir die produksie van amino sure gebruik was. In die teenwoordigheid van sout was koolstof moontlik gebruik om organiese sure te vervaardig wat koolstof weggeneem het van die vervaardiging van amino sure. Daar is tot die slotsom gekom dat mikorrhizas voordelig is vir die groei van plante onder toestande van sout stres mits daar 'n addisionele bron van koolstof teenwoordig is. Arbuskulere mikorrhiza infeksie het 'n geringe invloed gehad op die opname van voedingstowwe van plante wat in waterkultuur gegroei was.

Maintenance of normal health requires an intact stress system capable of mounting the metabolic, autonomic, behavioural and motor responses required for coping with or avoiding physiological and pathological challenges. The neuroendocrine component of this response principally involves the hypothalamic-pituitary-adrenal (HPA) and sympatho-adrenomedullary (SAM) axes. Impaired regulation of these axes has been implicated in the pathogenesis and expression of numerous disease states, however, it has proved very difficult to reproducibly activate the HPA and SAM axes and no single test exists that can reliably and safely be used to study these systems in man. Carbon dioxide (CO2) is the principal regulator of respiration, acid-base balance and behavioural-state arousal in humans. Paradigms of CO2 inhalation have been used in psychiatric research to investigate panic and anxiety disorders, but evaluation of other components of the stress response to CO2 has not previously been performed. I hypothesised that a single breath of 35% CO2 would be a simple and reliable tool for the evaluation of the stress response in humans. A single breath of four doses of CO2 (5%, 25%, 35% and 50%) was administered to 9 healthy volunteers in a randomised, single blind fashion. Subjective symptoms of anxiety increased in a dose-dependent manner. Inhalation of a single breath of 35% CO2 stimulated significant ACTH (p = 0.006), noradrenaline (p < 0.0001), cortisol (p = 0.02) and prolactin (p = 0.002) release. It also provoked an acute pressor response and an associated bradycardia (p < 0.0001 for both). No significant habituation of psychological, HPA or cardiovascular responses was seen when this dose was repeated after one week (n = 10) or 6 months (n = 5). It was apparent that a single breath of 35% CO2 reliably and safely produced SAM and HPA axis activation and further studies were then undertaken to assess the mechanism by which the observed responses occurred and its potential clinical implications. Administration of naltrexone (an opiate antagonist) to 10 normal volunteers disinhibited the HPA axis (p < 0.0004), whilst administration of metyrapone (a cortisol synthesis inhibitor) significantly reduced baseline cortisol (p < 0.03) levels. However, this alteration in HPA axis activity had no effect on either cardiovascular or psychological responses. Further, in a study of 8 breastfeeding mothers (a state associated with physiological suppression of the HPA axis) suckling significantly reduced plasma cortisol levels compared with control (p = 0.002) and bottle-feeders (p = 0.003). Despite this cortisol, systolic blood pressure (SBP), heart rate and psychological responses to 35% CO2 were not affected

Thesis (M.Tech.: Radiography)-Dept. of Radiography, Durban University of Technology, 2006 xi, 86 leaves, Annexures A-Q<br>The study will determine the sulphur dioxide (SO2) levels in the x-ray department and evaluate it’s effects on the health of the radiology workers. The aim of the study is to mainly create awareness of occupational hazards posed by processing chemistry to radiology workers.

碩士<br>國立中興大學<br>植物病理學系<br>85<br>This paper deals with the sensitivities of tomato varieties or lines to sulfur dioxide or ozone under natural illumination in the glass houses. The symptoms induced by sulfur dioxide usually consisted of water soaking, decoloration, white spots, yellowing, brownish blotches and leaf curl, and symptoms induced by ozone were white-fog-like blotches, water soaking blotches, brownish blotches, leaf curl and yellowing. The main difference between symptoms induced by both pollutants is that the boundary of symptoms induced by sulfur dioxide is more apparent than those induced by ozone. Wide differences in varietal or line sensitivity were observed among 142 lines tested. L70 the most tolerant and L82 the most sensitive were selected from this test. These two lines were examined for their physiological and biochemical responses after fumigated with sulfur dioxide and ozone. The change of stomatal conductance was related to the appearance of visible symptoms and the intercellular pH value after fumigated with sulfur dioxide. Sulfur dioxide at 800 ppb caused a significant increase in stomatal conductance of tolerant variety L70 on fifth day and the visible leaf injury appeared on sixth day after fumigation. Sulfur dioxide also caused a significant increase in stomatal conductance of sensitive variety L82 on the first day and the visible leaf injury appeared on the second day after fumigation. The maximum decrease of leaf intercellular pH value was concomitant to the maximum increase of stomatal conductance of tolerant variety 5 days after fumigated with 800 ppb sulfur dioxide. Leaf intercellular pH values increased proportionally with the duration of fumigation with sulfur dioxide on both tested varieties, however, sensitive variety decreased more prominent than tolerant one. Stomatal conductance of two tested varieties decreased after fumigation with ozone. Fumigation with low concentration of sulfur dioxide 200 ppb was more differentiable on the enzyme activities between tolerant and sensitive varieties. Peroxidase (POD) and glutathione reductase activities of tolerant variety were higher than those of sensitive one after fumigated with low concentration of sulfur dioxide. There was a negative correlation between the accumulation of malondialdehyde (MDA) and activity of POD after fumigated with low concentration of sulfur dioxide, increase in POD activity of tolerant variety resulted in no accumulation of MDA, and decrease in POD activity of sensitive variety resulted in accumulation of MDA.. There was no MDA accumulation in both tested tomato varieties after treated with ozone. However, activities of glutathione reductase, POD and catalase increased during ozone fumigation. Tolerant variety formed more ethylene than sensitive one during fumigation of sulfur dioxide or ozone.

碩士<br>國立屏東科技大學<br>森林系<br>94<br>Sulfur dioxide is one of the major air pollution sources in Taiwan. It has effects on the morphology, physiology, and biochemical activities of plants. In this experiment, 17 species of tree seedlings were chosen. They were fumigated, under controlled environment, with 600, 1000, and 2000 ppb of SO2 for two days. We compared injury symptoms of leaves and calculated injury index of different species. We also measured the net photosynthetic rate, stomatal conductance, chlorophyll concentration and chlorophyll fluorescence (Fv/Fm) of each species. These results can be used to determine the sensitivity and tolerance of each tested species to SO2. After being fumigated with 600 ppb SO2 for 48 hours, leaves of all species did not show any injury symptoms. But the net photosynthetic rates and stomatal conductance of Delonix regia, Lagerstroemia speciosa and Ficus septica reduced to less than 45%, while the other species reduced only slightly, comparing to the condition before treatment. When the SO2 concentrations were increased to 1000 ppb, there were no symptoms appearing on the leaves of Pistacia chinensis, but some white or ashen spots appeared on the leaves of Melia azedarach and Koelreuteria henryi, and some brown spots appeared on the leaves of the other 14 species. The plant injury index of P. chinensis and Liquidambar formosana were the slightest, while that of K. henryi was the most serious. Although the plant injury index of F. septica was only 20%, its relative photosynthetic rates and stomatal conductance drastically reduced to lower than 25%. The plant injury index of D. regia and L. speciosa were more than 90%, and their relative photosynthetic rates and stomatal conductance reduced further to lower than 10%, indicating these two species were the most seriously injured. The plant injury index of L. formosana, Nageia nagi and Diospyros maritima were only less than 30%, and their physiological activities could still maintained at more than 70% of what was before treated with 1000 ppb SO2. When the SO2 concentrations were increased to 2000 ppb, all the leaves in D. regia, L. speciosa and F. septica were obviously injured and fell off, while the leaves in the other species did not fall off. However, relative photosynthetic rates and stomatal conductance were all lower than 30%. The results showed that D. regia, L. speciosa and F. septica were the most sensitive species to SO2, either physiologically or morphologically. L. formosana, N. nagi and D. maritima were the most tolerant species to SO2, so that they can be planted in an environment of higher SO2. Four physiological activities, including net photosynthetic rate, stomatal conductance, chlorophyll concentration and chlorophyll fluorescence of each species in various concentrations of SO2 were compared. We found that, when treated with 600 ppb SO2, the chlorophyll concentration and chlorophyll fluorescence (Fv/Fm) of all species were not obviously changed, but the net photosynthetic rates and stomatal conductance were suppressed by SO2. When the SO2 concentrations were increased to 1000 ppb, chlorophyll fluorescence (Fv/Fm) could serve as an index for assessing plant tolerance to SO2. If the net photosynthetic rates and stomatal conductance were also taken into consideration, they would serve as an index of sensitivity and tolerance of plants to SO2. When the SO2 concentrations were increased to 2000 ppb, the leaves of D. maritime, L. speciosa and D. regia all fell off, while the chlorophyll concentration of other species still maintained above 70%. These result showed that chlorophyll concentration was not a physiological index to assess plant tolerance to SO2.

Thesis (MSc. (Horticulture)) -- University of Limpopo, 2019<br>After harvesting litchi fruit, the red pericarp colour is rapidly lost resulting in discolouration and browning during storage and marketing. To mitigate this challenge, the South African litchi industry uses sulfur dioxide fumigation to retain litchi fruit red pericarp colour during extended storage and shelf-life. However, there are health concerns regarding the commercially used (SO2) fumigation for litchi pericarp colour retention due to high levels of SO2 residues in fruit aril. Therefore, this study aimed to explore the possibility of Uvasys slow release SO2 sheets to retain ‘Mauritius’ litchi fruit red pericarp colour when packaged in plastic-punnets and bags. Treatment factors were two packaging materials (plastic-punnets and bags), six SO2 treatments (control; SO2 fumigation and four SO2 sheets viz. Uva-Uno-29% Na2S2O5; Dual-Release-Blue35.85% Na2S2O5; Slow-Release-36.5% Na2S2O5 and Dual-Release-Green-37.55% Na2S2O5) and four shelf-life periods (day 0, 1, 3 and 5). ‘Mauritius’ fruit were assessed for pericarp Browning Index (BI), Hue angle (ho), Chroma (C*) and Lightness (L*). In this study, an interactive significant effect (P < 0.05) between packaging type and SO2 treatments was observed on ‘Mauritius’ fruit pericarp L*, C* and ho during shelf-life. Fruit stored in plastic-bags and treated with SO2 fumigation showed higher pericarp C* and L*, while SO2 fumigated fruit in plastic-punnets had higher pericarp ho. Lower pericarp BI was observed in SO2 fumigated fruit stored in plastic-bags, which showed less pericarp browning than fruit in other treatments. In general, commercial SO2 fumigation resulted in lower pericarp BI, and higher pericarp L*, C* and ho throughout the storage and shelf-life. Our correlation analyses results further showed that litchi fruit red pericarp colour was better preserved as SO2 treatment levels increased, especially in plastic-bags. In retaining ‘Mauritius’ litchi fruit red pericarp colour, Uvasys SO2 sheets were not effective when compared with commercial SO2 fumigation. However, commercially SO2 fumigated fruit were bleached throughout the storage and shelf-life. Furthermore, fruit from all treatments were spoiled due to decay and mould growth after day 5 of shelf-life. Inclusion of pathogen protectants is important in future research to demonstrate whether Uvasys SO2 sheet-packaging technology can retain ‘Mauritius’ litchi fruit pericarp colour.<br>Agricultural Research Council and National Research Foundation (NRF)

Since plants utilize CO��� as the substrate for photosynthesis, terrestrial plants may be directly affected by increasing levels of CO��� in the atmosphere. Plants native to the sagebrush steppe are predicted to increase in growth in response to elevated CO��� through increased water use efficiency and higher photosynthetic rates. This study examined the interactions between edaphic factors and CO��� in order to determine how species native to the sagebrush steppe may respond to elevated CO���. The objectives of these experiments were to: 1. determine if Sitanion hystrix, Artemisia tridentata ssp. wyomingensis, and Stipa thurberiana alter their growth and physiology in response to CO��� and soil temperature. 2. determine if Sitanion hystrix and Artemisia tridentata ssp. wyomingensis alter their growth and physiology in response to CO��� and water stress. Two experiments were conducted using environmentally controlled chambers. In the first experiment, Sitanion hystrix, Artemisia tridentata and Stipa thurberiana were exposed to ambient (374 ppm) or high (567 ppm) CO��� conditions and low (13��C) or high (18��C) soil temperature. After four months in the chambers, plants were harvested and plant material was divided into shoots, roots, and leaves. Results from the first experiment demonstrated that carbon dioxide and soil temperature modified the growth of these species. Sitanion hystrix increased its shoot and root weights at elevated CO��� when grown under low soil temperatures. Artemisia tridentata had lower plant weights under elevated CO��� and 18 ��C soil temperature than plants grown at ambient CO��� and 13��C. Shoots of Stipa thurberiana were responsive to soil temperature and roots were responsive to CO��� at 18��C. In the second experiment, Sitanion hystrix and Artemisia tridentata were exposed to ambient (371 ppm) or high (569 ppm) CO��� and well-watered or water stressed conditions. Results indicated that there were no interactive effects betweeen CO��� and water stress with respect to plant growth or physiology. CO��� increased water use efficiency in S. hystrix and increased water use efficiency of A. tridentata at the beginning of the experiment but had no interactive effects with water stress on growth or photosynthesis. Results suggested that the effect of CO��� on plant growth and productivity of the sagebrush steppe is dependent upon the soil temperature to which the plants are exposed. Differences between species in their response to CO���, soil temperature, and water stress were also apparent in this experiment. These controlled environment studies should pave the way for field studies in the sagebrush steppe in order to determine if differences in carbon allocation, resulting from changes in CO��� and soil temperature, are realized in the field. Alterations in carbon allocation may potentially alter the competitive relationships between species and influence successional processes in the sagebrush steppe.<br>Graduation date: 1997

A forest’s ability to sequester carbon dioxide depends on factors such as periodic disturbance regimes, land-use change, the composition and productivity of the vegetative community, and the location and age of forested stands. However, one of the driving forces that contributes to changes in forest carbon dynamics include climatic factors, such as changes in temperature and precipitation, as well as atmospheric CO₂ concentrations which can affect the physiology of plants in complex ways. Our theorized understanding of plant physiological response to changing environmental conditions have been based on latitudinal and altitudinal studies or greenhouse experiments that measure plant physiological traits on one or a handful of plant species – and as scientists work to reduce the large variability that exists behind climate projections and plant community predictions, the need to collect locational and species-specific data becomes increasingly evident. This dissertation aims to address this issue by examining the physiological responses to temperature for 23 different tree species that have historically different geographic range distributions categorized into three groups: northern, central, and southern. The ranges of all species overlap and coexist at Black Rock Forest (BRF), an eastern deciduous forest located in the Hudson Highlands of New York. Chapter 1 examines the physiology of 16 coniferous and broadleaved tree species to determine if geographic provenance has a significant effect on foliar respiration rates, response to elevated temperature, and the respiratory substrate used to fuel the respiratory process. Chapter 2 compares the photosynthetic capacities and temperature responses of 17 broadleaved tree species to determine which range group may be more tolerant of a warming climate. Appended to this dissertation is preliminary data of a growth chamber experiment, examining the plasticity of physiological traits expressed under elevated temperatures to assess whether northern red oak seedlings show potential to acclimate to projected climate conditions and regenerate with minimal physiological constraints. Collectively, the results of these studies find significant differences in photosynthetic capacities and photosynthetic and respiration responses to temperature among species and among range groups. Northern, central, and southern ranged trees show an acclimated response to carbon assimilation under current climate conditions. However, central ranged trees, which includes the northern red oak, a dominant tree species in this region of New York, may be at a physiological disadvantage, showing lower rates of photosynthetic capacities and a trending decline of carbon assimilation under elevated temperatures. Furthermore, preliminary data from a greenhouse experiment suggests that leaf morphology and physiology traits are not plastic for northern red oak seedlings, which further weakens its physiological competitiveness and regeneration potential under warming temperatures. The results presented in this study on the physiological traits and temperature responses not only allows for a more thorough understanding of the physiological tolerances of migrant and resident tree species in the New York region but provides new data that could be incorporated into carbon and species distribution models for better predictions on carbon sequestration of forests and geographic ranges of tree species.

Chapter 1. Background: Asthma is the most common chronic childhood disease and is characterized by recurrent airway obstruction, bronchial hyper-responsiveness, and airway inflammation. Asthma is the leading cause of childhood hospitalization and school absenteeism in the United States. The associations between adverse respiratory effects and exposure to indoor nitrogen dioxide (NO2) and other byproducts of combustion such as particulate matter (PM) in particular ultrafine particulates (UFP), Ozone (O3) and Sulfur Dioxide (SO2), have been the focus of many epidemiological studies in recent years. Indoor exposure to NO2 and other pollutants from combustion may increase the risk of acute and chronic respiratory disease, reduce lung function, initiate and exacerbate asthma in children. The levels of exposure to NO2 indoors are of public health concern because children spend nearly 70% of their time indoors at home. According to the 2010 US Census report, approximately 39% of US households use natural gas for cooking, and the primary source of residential NO2 is a gas-fuel cooking appliance. Indoor levels of NO2 where NO2 sources are present can be much higher than outdoors, where the primary source of NO2 is vehicular traffic. Epidemiological studies in developed countries suggest that gas stoves used for cooking and/or heat are associated with an increased risk of asthma and respiratory symptoms in children. While there are numerous, epidemiological studies supporting an association between increased NO2 levels and gas stoves and asthma symptom severity in children, there are other studies that have examined the relationship in homes that did not observe significant associations. A better understanding of how NO2 and other indoor environmental (e.g., environmental tobacco smoke (ETS), allergens) exposures contribute to asthma morbidity in inner city preschool children will allow interventions to more effectively designed and implemented. To date, there are conflicting results on the role of exposure to indoor NO2 and its association with new-onset asthma in young inner-city children. The recent studies assessing the effects of indoor NO2 on asthma morbidity were limited to inner-city children, largely older, who were diagnosed with asthma. A gap in knowledge remains regarding the role indoor NO2 plays on the development of asthma in children not previously diagnosed. The scientific and public health rationale for conducting this dissertation was to describe the association of exposure to indoor NO2 and primary sources with the initiation and exacerbation of asthma symptoms among pre-school children with and without diagnosed asthma. The data analyzed in the current research come from a larger study of Endotoxin, Obesity, and Asthma (EOA) in the New York City Head Start Program, funded in the summer of 2002. The primary research objective of that study was to identify modifiable risk factors associated with asthma and asthma persistence among preschool children from low-income families living in select New York City neighborhoods with high pediatric asthma hospitalization rates. We conducted a cross-sectional analysis of data collected from the study questionnaire and home visit sampling at study enrollment. The analyses were performed in two phases: the first phases used data collected at study enrollment and the second phase used data collected 12-months after study baseline. Henceforth, the dissertation will refer to the first analyses as the baseline study and the second as the follow-up study. The research evaluated the association of NO2 exposure with asthma status among New York City Head Start children with and without asthma at study enrollment and with respiratory symptoms among children with asthma at 12-month follow-up. Chapter 2. Baseline Study: We conducted a cross-sectional analysis of data collected from the study questionnaire and home visit sampling at study enrollment. Specifically, the research sought to evaluate the association of NO2 exposure with asthma status among New York City Head Start children with and without asthma at study enrollment and with respiratory symptoms among children with asthma at enrollment. A total of 503 children were included in the baseline study. A total of 105 children (20.9%) met the criteria for both asthma and allergy, and 67 (13.3%) met the criteria for asthma alone. Girls made up 51.7% and boys, 48.3% of the 503 study participants. Descriptive analyses suggested that asthma/allergy status was associated with: male gender, non-Mexican ethnicity/national origin, presence of a smoker in the child’s home, number of smokers in the child’s home, self-reported parental history of asthma, mother’s education level and sensitization to one or more of the four allergens. Logistic regression models were used to investigate the magnitude and direction (as well as trend) of the association between childhood asthma and indoor NO2 sources in the child’s home. Chapter 3. Follow-up Study: Our follow-up study involved the analysis of the 12-month follow-up data from the study of Endotoxin, Obesity, and Asthma in the New York City Head Start Program funded in the summer of 2002. We focused on assessing the magnitude and direction of the associations of exposure to indoor NO2 levels (based on baseline NO2 measurements) with children’s asthma status and with symptom severity among asthmatics at 1-year follow-up. For the follow-up study, we categorized children by whether their asthma status had changed since baseline. Descriptive analyses were performed looking at key characteristics by “change in asthma status.” Children’s asthma status at baseline and at follow-up, were based on responses to the questionnaire. We analyzed indoor NO2 level measurements at baseline in relation to asthma outcomes on follow-up. We did not have enough data on NO2 levels at follow-up to analyze them in relation to asthma status on follow-up. Unless the family had relocated since baseline and/or reported changes since baseline in the use of gas appliances or the number of smokers in the home, we assumed that baseline NO2 levels in the participating children’s homes were reasonable proxies for current exposures. We looked at the number of children who moved since baseline and whether the move (for example, looking at gas stove status, age of new building) may have impacted indoor NO2 levels. Of the 503 children who were included in the baseline analyses, 47.3% had data on asthma status on follow-up. A total of 238 children (111 male, 127 female) were grouped into the four mutually exclusive outcome categories: 122 (51.3%) did not have asthma at baseline or on follow-up, 34 (14.3%) had asthma on follow-up but not at baseline, 65 (27.3%) had asthma at baseline but not on follow-up, and 17 (7.1%) had asthma at baseline and on follow-up. The mean age at 1-year follow-up was 59.5 months (6.95), and neither age nor gender was associated with asthma. The distribution of ethnicity/national origin among the 238 children remained the same as at baseline; no one ethnicity group experienced disproportionate loss to follow-up, and asthma status remained associated with non-Mexican ethnicity/national origin, although 44.1% with new-onset asthma were of Mexican background. Asthma was also associated with self-reported parental history of asthma and allergy in children, but nearly 80% of children with new-onset asthma had no such parental history of asthma. More parents of children with new-onset (35.3%) or persistent asthma (23.5%) than of other children reported making efforts to reduce risk factors or triggers for asthma exacerbations in the past 12 months. Chapter 4. Dissertation Conclusion : The primary objective of the dissertation research was the examination of the relationship between asthma and asthma severity and exposure to gas cooking and residential NO2. In both our baseline and 12-month follow-up studies, exposure to indoor NO2 was represented by the baseline measurement of NO2 and the NO2 surrogate, gas stove. Asthma status of children was based on parental responses on the questionnaire regarding asthma symptoms and urgent care visits due to respiratory distress over the course of each 12-month period prior to the conducting study questionnaires. For both studies, we did not find an association between exposure to NO2 levels at baseline and asthma status or severity. Our findings contradict the results of most recent studies of both NO2 levels and residential sources of NO2 and their effects on asthma symptoms in very young children. However, it remains difficult to compare our results we those of previous published studies because those studies primarily focused on children who were diagnosed with asthma, whereas our research included preschool aged children with and without asthma. Based on our findings and the fact they conflict with other epidemiological studies, of which there were also conflicting results, we feel that the relationship between asthma symptoms and NO2 exposures remains ambiguous. The lack of consistent results of epidemiological research raises questions that should be the focus of future epidemiological studies. What are the roles of co-pollutants and co-risk factors? Does NO2 work alone or in concert with other indoor pollutants? There exists a real lack of understanding on the possible synergistic effects of exposure to NO2 and other combustion byproducts. Important to furthering our knowledge of the role of exposure to indoor NO2 and asthma is determining whether NO2 acts as a surrogate for co-pollutants that are considered risk factors for asthma and other respiratory conditions. Another focus of future indoor pollution studies should be the development of effective methods and technologies for measuring the constituents of the complex mixture of pollutants in indoor air; these methods and technologies can then be applied in personal monitoring of exposure to indoor pollutants in epidemiological studies that would help to determine with much more accuracy the effects of individual indoor pollutants on asthma and other respiratory symptoms. This knowledge would help in the development of more effective public health and environment policies towards reducing the burden of childhood asthma.