Plankton metabolic balance (PMBm) of the surface mixed layer was calculated as the ratio of areal rates of gross photosynthesis (AGP) to community respiration (AR), and estimated for four Laurentian Great Lakes coastal sites of contrasting physical, optical and nutrient regime: western Lake Ontario, Hamilton Harbour, Georgian Bay and Woods Bay. The applied methods were the oxygen light-and-dark bottle and 14C bottle methods as well as the oxygen stable isotope method (18O method). PMBm was net autotrophic in most of the cases (73% of the observations). Within- and inter-system variations in PMBm were heavily dependent on both a ratio of light-saturated photosynthesis to community respiration (Pmax/R) and a ratio of euphotic to mixing depths (Zeu/Zm). While short-term within-system variations in PMBm were driven by the interplay of chlorophyll a (Chl a), total phosphorus (TP) and Zeu/Zm ratio, its inter-lake long-term variability had a different behaviour. Average ratios of AGP/AR were dependent only on DOC or single physical parameters such as Zeu or Zm, while PMBm determined as the ratio between average AGP and AR was controlled by the joint effect of DOC, TP and Chl a. DOC affected average AGP/AR ratios primarily via its control over fluctuations of the physical environment and had a depressing effect on AGP rates but did not control rates of AR. Independent measurements of volumetric rates of photosynthesis (P) and community respiration (R) were made by 18O method adjusted for wind-driven gas exchange and compared against estimates from bottle estimates. The 18O method in Lake Ontario gave internally inconsistent results (e.g. negative absolute rates of P and R) and poor agreement with independent estimates of P, R and P/R despite superficially plausible estimates for P/R. The low productivity of Lake Ontario and frequent disturbances of water column masked the biological signal in both DO abundance and its isotopic signature, and thus invalidated the assumptions of steady state conditions. However, in Hamilton Harbour and some other relatively sheltered sites that were sampled occasionally, 18O method predicted absolute rates of P that were well correlated well with bottle estimates. Isotope model estimates for R and P/R in the harbour were not well correlated with bottle estimates but were of comparable magnitude on average, and differences were explicable in terms of physical forces and the different time scales of response for the two methods. The Hamilton Harbour hypolimnion presented an anomalous behavior in oxygen stable isotopes (18O depletion) where seasonal development of DO depletion was not accompanied by the progressive isotope enrichment expected from respiratory fractionation. The Lake Ontario and harbour hypolimnion results both appear to show that simple steady state models that assume literature values for fractionation processes and ignore physical dynamics are of limited applicability to lakes.

Plankton metabolic balance (PMBm) of the surface mixed layer was calculated as the ratio of areal rates of gross photosynthesis (AGP) to community respiration (AR), and estimated for four Laurentian Great Lakes coastal sites of contrasting physical, optical and nutrient regime: western Lake Ontario, Hamilton Harbour, Georgian Bay and Woods Bay. The applied methods were the oxygen light-and-dark bottle and 14C bottle methods as well as the oxygen stable isotope method (18O method). PMBm was net autotrophic in most of the cases (73% of the observations). Within- and inter-system variations in PMBm were heavily dependent on both a ratio of light-saturated photosynthesis to community respiration (Pmax/R) and a ratio of euphotic to mixing depths (Zeu/Zm). While short-term within-system variations in PMBm were driven by the interplay of chlorophyll a (Chl a), total phosphorus (TP) and Zeu/Zm ratio, its inter-lake long-term variability had a different behaviour. Average ratios of AGP/AR were dependent only on DOC or single physical parameters such as Zeu or Zm, while PMBm determined as the ratio between average AGP and AR was controlled by the joint effect of DOC, TP and Chl a. DOC affected average AGP/AR ratios primarily via its control over fluctuations of the physical environment and had a depressing effect on AGP rates but did not control rates of AR. Independent measurements of volumetric rates of photosynthesis (P) and community respiration (R) were made by 18O method adjusted for wind-driven gas exchange and compared against estimates from bottle estimates. The 18O method in Lake Ontario gave internally inconsistent results (e.g. negative absolute rates of P and R) and poor agreement with independent estimates of P, R and P/R despite superficially plausible estimates for P/R. The low productivity of Lake Ontario and frequent disturbances of water column masked the biological signal in both DO abundance and its isotopic signature, and thus invalidated the assumptions of steady state conditions. However, in Hamilton Harbour and some other relatively sheltered sites that were sampled occasionally, 18O method predicted absolute rates of P that were well correlated well with bottle estimates. Isotope model estimates for R and P/R in the harbour were not well correlated with bottle estimates but were of comparable magnitude on average, and differences were explicable in terms of physical forces and the different time scales of response for the two methods. The Hamilton Harbour hypolimnion presented an anomalous behavior in oxygen stable isotopes (18O depletion) where seasonal development of DO depletion was not accompanied by the progressive isotope enrichment expected from respiratory fractionation. The Lake Ontario and harbour hypolimnion results both appear to show that simple steady state models that assume literature values for fractionation processes and ignore physical dynamics are of limited applicability to lakes.

Microalgae are an important potential feedstock for biodiesel production. Understanding the physiology of lipid biosynthesis in microalgae is pivotal to microalgal aquaculture management. A freshwater green microalga strain, UTEX 2219-4, was isolated from UTEX 2219 which was reported containing two strains. Its ITS sequences are closely related to those in the family of Scenedesmaceae in the GenBank. Nitrogen starvation, salt stress and osmotic stress greatly enhanced lipid biosynthesis in this strain, while combination of nitrogen deficiency and osmotic stress had the most dramatic effect. Chloroplast was condensed and photosynthesis efficiency declined about 50% after 3 days of nitrogen starvation. Chlorophyll degradation followed the same trend but was more severe than the reduction of photosynthesis efficiency. Oil body formation was not observed in the cells kept in the dark under nitrogen starvation, suggesting photosynthesis rather than autophagy is the major player in oil body formation. Under non-saturation levels of light intensities coupled with nitrogen starvation, the oil body formation under 150 £gmol/m2s light intensity was more efficient than that under 75 £gmol/m2s. DCMU blocked photosynthesis as well as oil body formation, supporting that the energy for oil body formation was mostly from photosynthesis rather than autophagy during nitrogen starvation.

Thesis (Ph. D.)--University of Chicago, Department of the Geophysical Sciences, 2002. / Includes bibliographical references. Also available on the Internet.

No description available.

Global modeling of gross primary production (GPP) is a critical component of climate change research. On local scales, GPP can be assessed from measuring CO₂ exchange above the plant canopy using tower-based eddy covariance (EC) systems. The limited footprint inherent to this method however, restricts observations to relatively few discrete areas making continuous predictions of global CO₂ fluxes difficult. Recently, the advent of high resolution optical remote sensing devices has offered new possibilities to address some of the scaling issues related to GPP using remote sensing. One key component for inferring GPP spectrally is the efficiency (ε) with which plants can use absorbed photosynthetically active radiation to produce biomass. While recent years have seen progress in measuring ε using the photochemical reflectance index (PRI), little is known about the temporal and spatial requirements for up-scaling these findings continuously throughout the landscape. Satellite observations of canopy reflectance are subject to view and illumination effects induced by the bi-directional reflectance distribution function(BRDF) which can confound the desired PRI signal. Further uncertainties include dependencies of PRI on canopy structure, understorey, species composition and leaf pigment concentration. The objective of this research was to investigate the effects of these factors on PRI to facilitate the modeling of GPP in a continuous fashion. Canopy spectra were sampled over a one-year period using an automated tower-based, multi-angular spectroradiometer platform (AMSPEC), designed to sample high spectral resolution data. The wide range of illumination and viewing geometries seen by the instrument permitted comprehensive modeling of the BRDF. Isolation of physiologically induced changes in PRI yielded a high correlation (r²=0.82, p<0.05) to EC-measured ε, thereby demonstrating the capability of PRI to model ε throughout the year. The results were extrapolated to the landscape scale using airborne laser-scanning (light detection and ranging, LiDAR) and high correlations were found between remotely-sensed and EC-measured GPP (r²>0.79, p<0.05). Permanently established tower-based canopy reflectance measurements are helpful for ongoing research aimed at up-scaling ε to landscape and global scales and facilitate a better understanding of physiological cycles of vegetation and serve as a calibration tool for broader band satellite observations.

The C3 photosynthetic pathway uses light energy to reduce CO2 to carbohydrates and other organic compounds and is a central component of biological metabolism. In C3 photosynthesis, CO2 assimilation is catalyzed by ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), which reacts with both CO2 and O2. While competitive inhibition of CO2 assimilation by oxygen is suppressed at high CO2 concentrations, O2 inhibition is substantial when CO2 concentration is low and O2 concentration is high; this inhibition is amplified by high temperature and aridity (Sage 2004). Atmospheric CO2 concentration dropped below saturating levels 25-30 million years ago (Tipple & Pagani 2007), and the C4 photosynthetic pathway is hypothesized to have first evolved in warm, low latitude environments around this time (Christin et al. 2008a). The primary feature of C4 photosynthesis is suppression of O2 inhibition through concentration of CO2 around Rubisco. This pathway is estimated to have evolved almost 50 times across 19 angiosperm families (Muhaidat et al. 2007), a remarkable example of evolutionary convergence. In several C4 lineages, there are species with photosynthetic traits that are intermediate between the C3 and C4 states, known as C3-C4 intermediates. In two eudicot genera, Flaveria (Asteraceae) and Alternanthera (Amaranthaceae), there is evidence that these species represented an intermediate state in the evolution of the C4 pathway (McKown et al. 2005; Sanchez-del Pino 2009). The purpose of this thesis is to ascertain the specific benefits to plant carbon balance and resource-use efficiencies of the C3-C4 pathway relative to C3 species, particularly at low CO2 concentrations and high temperatures, factors which are thought to have been important in selecting for C3-C4 traits (Ehleringer et al. 1991). This will provide information on the particular advantages of the C3-C4 pathway in warm, often arid environments and how these advantages may have been important in advancing the initial stages of C4 evolution in eudicots. This thesis addresses the physiological intermediacy of previously uncharacterized C3-C4 species of Heliotropium (Boraginaceae); the water- and nitrogen-use efficiencies of C3-C4 species of Flaveria; and the photosynthetic performance and acclimation of C3, C4 and C3-C4 species of Heliotropium, Flaveria and Alternanthera grown at low and current ambient CO2 levels and high temperature.

No description available.

1. Distribution of the two photosystems (PS I and PS II) in the thylakoid membranes of the alga Euglena gracilis. The distribution of photosystem I and II (PS I and PS II) in the alga Euglena gracilis Z strain was studied by electron microscopic immunocytochemistry. In this alga, the thylakoids are not organized in gram structures, as they are in higher plants. Two different antibodies were used to identify PS I. One is directed against particles of PS I from maize and the other against the 60 and 62 kDa PS I reaction centre proteins of the cyanobacterium Synechococcus elongatus. Both antibodies demonstrated the presence of PS I in the two types of thylakoid membranes, appressed (AM) and non-appressed (NAM). Quantitative analysis showed that 60--74% of PS I is in the AM and 26--40% is in the NAM, and since about 80--90% of the membranes are AM, that PS I is more concentrated in the NAM. An antibody directed against the CP47 protein of PS II also revealed labelling in both types of thylakoid membranes (54% in AM and 46% in NAM). PS II is again more concentrated in the NAM. I demonstrated by the photo-oxidation of 3,3'-diaminobenzidine that there is PS I activity in the two types of membranes and, moreover, that there are changes in this activity during the light cycle of the cell. My results indicate that the distribution of PS I and PS II in Euglena gracilis Z strain is different from that of higher plants and is similar to that seen in green algae. The possible evolutionary significance of our observations are discussed. / 2. Localization of the protein CP47 (plastid protein) in the mitochondria of euglenoids. The localization of the CP47 protein to the mitochondria of euglenoids was studied by electron microscopic immunocytochemistry. My results demonstrate that this protein, which is coded by chloroplast DNA in all algae and plants, is present in whole or in part in the mitochondria of Euglena gracilis and related euglenoids. I used two different antibodies against the protein CP47 (anti-CP47 from Chlamydomonas reinhardtii and S. elongatus) to test wild-type, light-grown, cells of Euglena. Both antibodies selectively labelled the mitochondria. These results furthermore suggest that this labelling is particularly associated with mitochondrial cristae. Anti-CP47 from S. elongatus also labelled the mitochondria of other euglenoids, such as dark-grown cells of Euglena gracilis, the mutant Y9Z1NaL, and Astasia longa. Since the CP47 protein is present in dark-grown cells and in the mutant Y9Z1NaL, which are organisms that do not have an active psbB gene, I suggest that a gene transfer has occurred from the plastid to the mitochondria during evolution. Because our results show the presence of CP47 in the mitochondria of Astasia longa, I postulate that the transfer occurred before the branching of Astasia from Euglena.

Integrated photoelectrochemical water splitting with sunlight is one possible solution to growing global energy needs. Integration of catalysts, photoabsorbers and a membrane require low barriers to charge dissipation if a free standing device structure is to be achieved. The n-type/PEDOT:PSS junction has be identified as the major resistive component and constitutes a large barrier to charge dissipation. In this thesis, the modification of the interface between n-type Si/PEDOT:PSS was achieved by growing a highly – doped region at the contact between the wire and the membrane to reduce voltage loss at the junction from 300 mV to 130 mV. In addition, modification of the surface using a thiophene moiety is observed to decrease the voltage loss from 300 mV to 30 mV. Formation of an insulating silicon oxide on the methyl functionalized surface of the microwires identified a need for characterization of planar silicon samples representative of the sides of the microwires. Si (110), (211) and (111) crystal faces were functionalized with a methyl group and showed different resistance to oxidation. The Si (111) surface was the most resistant while the Si (211) surface was observed to be the least resistant to ambient oxidation.