Cadmium (Cd), a cancer-causing heavy metal ion, concentration in the environment has recently shown a rapid increase mainly as a result of human activity. Since many plants are used as medicine and food, it is crucial to investigate effects of Cd on plant growth and development. This study examines the time course and concentration-dependent effects of Cd on morphology, photosynthesis and protein profiles in hydroponically-grown bean plants (Phaseolus vulgaris). High concentrations of Cd (1000 and 100uM) induced leaf wilting and reduced both leaf growth and photosynthesis rate within 24 and 48 hours respectively. Lower concentration of 10 uM Cd showed the wilted morphology after 96 hours. In addition, the Cd-induced changes in protein profiles especially the photosynthesis and stress proteins will be discussed in relation to morphology, leaf growth and photosynthesis in bean plants.

In order to predict future range shifts for invasive species it is important to explore their ability to acclimate to the new environment and understand physiological and reproductive constraints controlling their distribution. My dissertation studied mechanisms by which temperature may affect the distribution of two of the most aggressive plant invaders in North America, Bromus tectorum and Bromus rubens. While Bromus tectorum is dominant in the “cold desert” steppes of the Intermountain region of western North America, B. rubens is one of the severe grass invaders in the “hot deserts” of southwestern North America. I first evaluated whether winter freezing tolerance is the mechanism responsible for the distinct northern range limits of Bromus species. Bromus rubens has a slower rate of freezing acclimation that leads to intolerance of sudden, late-autumn reductions in temperature below -12°C, Bromus tectorum, by contrast, cold hardens rapidly and is not impacted by the sudden severe late-autumn cold. Photosynthetic response to temperature does not explain their current range separation. Bromus species differ little in their photosynthetic temperature responses and the acclimation pattern of photosynthesis. Both species acclimated to a broad range of temperature through the amelioration of Pi regeneration limitation at sub-optimal temperatures and improved carboxylation capacity above the thermal optimum which probably resulted from increased thermostability of Rubisco activase. The effect of elevated temperatures during flowering on the seed yield of Bromus species demonstrates that neither species produces seed at 36°C and above. These thresholds are close to temperatures encountered during flowering in their natural environment. In summary, climatic changes will cause northward range expansion of Bromus species due to less severe autumn and winter, while reproductive failure could cause range contraction at their southern margins.

Research was conducted to determine individual suitability of native and Canadian-bred selected plants in terms of growth and survivability for local extensive green roofs. The experiment was single-factor (species) with 12 levels (two Sedum spp. [controls]; 10 Canadian-bred or native plant species) in a randomized complete block design with three blocks. Variables measured were percent survival and cover, height, fresh and dry weights, stomatal conductance, transpiration, photosynthetic rate, soil temperature, soil moisture, and reflectance. Artemisia stelleriana contributed more to cooling through transpiration than Sedum floriferum, and maintained similar soil moisture to Sedum acre. Lotus corniculatus was similar to the controls in photosynthetic rate and had higher reflectance than Sedum acre in July. With high biomass and photosynthetic rates, Aster novi-belgii may contribute more to carbon sequestration and insulation than the controls. Artemisia stelleriana , Lotus corniculatus, and Aster novi-belgii are suitable species for extensive green roofs in northern Nova Scotia.

In an effort to contribute to the improvement of Matric Biology education, a survey was conducted in 1996 and 1997 of Matric pupils and first year students at several tertiary institutions, in order to identify those topics which learners found most difficult. Photosynthesis and respiration were among the topics with which Matric Biology learners experienced many conceptual difficulties. The aim of this project was twofold: firstly to identify specific misconceptions students had regarding these topics, and secondly, to develop and evaluate a learning tool that would address these misconceptions. In order to identify the most common specific misconceptions, a quantitative research approach was taken. A three-tiered multiple choice questionnaire was developed, and administered to first year students in the 1998 intakes at MLSultan Technikon and the Biology Department of the University of Natal, Durban. It was also administered to students at the end of their first, second and third years of Cell Biology (University of Natal), Analysis of the questionnaires revealed that students did not understand the complementary relationship between photosynthesis and respiration. Computer-based virtual worlds provide constructivist learning environments, in which visualisation and problem solving in a complex system is possible. It was proposed that use of a virtual world would be an effective means of addressing the misconceptions we identified. A game was developed that presented students with authentic tasks of filling an oxygen cylinder (as an air supply) and a carbon dioxide cylinder (which would later be used to extinguish a fire). In order to do this students were required to solve a series of three puzzles, all of which related to the processes of photosynthesis and respiration. To account for different learning styles, the puzzles were based on three of Gardner's multiple forms of intelligence. Evaluation of the virtual world made use of a combination of quantitative and qualitative research methods. Students' understanding of the processes was measured with the use of the questionnaire. A deeper evaluation of their understanding and affective response to the game was obtained through interviews. It was found that students who had played the game had a clearer understanding of the complementary relationship between photosynthesis and respiration, and understood that respiration in plant cells is a continuous process. Students also showed greater confidence in their grasp of the processes, and reported that playing the game had been an enjoyable way of complementing their traditional lecture material in order to master these concepts. The virtual world was an effective learning tool for addressing the misconceptions students held regarding photosynthesis and respiration. / Thesis (M.Sc.)-University of Natal, Durban, 1998.

The increasing demand for energy and the pressure to reduce reliance on fossil fuels encourages the development of devices to harness clean and renewable energy. Solar energy is a large enough source to fulfill these demands, however, in order to overcome its daily and seasonal variability, it has been proposed that sunlight be harvested and stored in the form of chemical fuels. One potential approach is the photosynthetic splitting of water to store solar energy in the simplest chemical bond, H–H, using a device that includes: semiconducting microwire arrays as light harvesting components, redox catalysts, and a membrane barrier for separating the products of water redox reactions.. However, the harvested solar energy can be lost across the system and it is critical to characterize the electrical properties of each component within the system to quantify how much of this energy will ultimately be coupled to the water splitting reactions. The aim of this research is to develop approaches for characterization of a proposed system of this kind, incorporating individual semiconductor microwires as photoelectrodes (with no redox catalysts) embedded into a candidate conducting polymer membrane to form a single functional unit. Semiconductor microwires were isolated and using a novel contact formation approach with tungsten probes in a standard probe station, and their current versus voltage properties were characterized. This approach is of particular interest when ii considering the limitations of conventional contact formation approaches (e.g. thermal evaporation of contact metals), arising from the small dimensions of the microwires and also the incompatibility of these techniques with many microwire/polymer structures due to the unwanted interactions between polymers, photoresists, etchants and the high temperature lithographic processes. The electrical properties of different microwires and also the junctions between microwires and two candidate polymers were studied. Specifically, the combination of methyl-terminated silicon microwires and PEDOT:PSS:Nafion demonstrated promising behavior, with a total DC resistance of approximately 720 kΩ (i.e. losses < 16 mV at maximum available photocurrent), making it a suitable candidate for the use in the proposed system. The outcome of these research may be applied to many applications including semiconducting microstructures and conducting polymers.

The chloroplast originates from an endosymbiotic event 1.5 billion years ago, when a free living photosynthetic bacteria was engulfed by a eukaryotic host. The chloroplastic genome has through evolution lost many genes to the nuclear genome of the host. To coordinate the gene expression between the two genomes, plants have evolved two types of communication, nucleus-to-plastid (anterograde) and plastid-to-nucleus (retrograde) signalling. This thesis will focus on retrograde communication with emphasis on redox and tetrapyrrole mediated signalling. In this thesis, we establish the tetrapyrrole Mg-ProtoIX as an important retrograde negative regulator of nuclear encoded plastid proteins. We show that Mg-ProtoIX accumulates in both artificial and natural stress conditions, and that the accumulation is tightly correlated to regulation of nuclear gene expression. Using confocal microscopy, we could visualize Mg-ProtoIX in the cytosol during stress conditions. In addition, exogenously applied Mg-ProtoIX stayed in the cytosol and was enough to trigger a signal to the nucleus. The results presented here indicate that Mg-ProtoIX is transported out of the chloroplast to control nuclear gene expression. Mg-ProtoIX mediated repression of the nuclear gene, COR15a, occurs via the transcription factor HY5. HY5 is influenced by both plastid signals and the photoreceptors. Here, we show that photoreceptors are part of Mg-ProtoIX mediated signalling as well as excess light adaptation. We identified the blue light receptor, CRY1, as a light intensity sensor that partly utilizes HY5 in the high light response. To further understand the high light regulation of nuclear genes, we isolated a mutant with redox insensitive (rin) high light response. The rin2 mutant has a mutated plastid protein with unknown function. Characterization of the rin2 mutant revealed that the protein is important in regulating plastid gene expression as well as nuclear gene expression. The rin2 mutant is the first characterized rin mutant and could prove important in elucidating the cross-talk between redox mediated coordination between the plastid and the nuclear genome.

In New Zealand, native shrubs are considered an important potential carbon-sink in disturbed or abandoned land (e.g., pastoral land that is unsustainable for long-term pastoral agriculture). However, the impact of varying environmental drivers on carbon uptake from photosynthesis and carbon loss from respiration of a developing shrubland remains uncertain. In this study, the effects of both temperature and soil water content (θ) on photosynthesis and respiration were examined under controlled growth cabinet and field conditions in a pasture grass and the native shrub, kānuka (Kunzea ericoides var. ericoides). The purpose of the investigation was to assess the combined impacts of varying temperature and θ on canopy processes and to disentangle the effects of θ on photosynthesis and respiration for the two different plant types. A controlled growth cabinet study (Chapter 2) showed that θ had a greater effect on the short-term temperature response of photosynthesis than the temperature response of respiration. The optimum value of θ for net photosynthesis was around 30 % for both kānuka and the grass. Statistical analysis showed that the temperature sensitivity of photosynthetic parameters was similar for both plant types, but the sensitivity of respiratory parameters was different. Reduction in θ induced an inhibition of photosynthetic capacity in both plant types. The response of respiratory parameters to θ was not related to substrate limitations, however available evidence suggests that it is likely to be a species dependent plant mechanism in regulating the cost of maintenance due to reduced photosynthate assimilation and decreasing energy supply to support the activity of respiratory enzymes. Results obtained from a field study (Chapter 3) showed that photosynthesis and respiration in the grass and kānuka were sensitive to seasonal changes in temperature and θ. Photosynthetic parameters showed little acclimation following changes in seasonal growth conditions. In contrast, respiratory parameters tended to acclimate more strongly. Respiratory acclimation to multiple environmental conditions was characterised by changes in temperature sensitivity and a shift in the response of respiration to temperature, demonstrating the involvement of both ‘Type I’ and ‘Type II’ acclimation in both plant types. The results from controlled growth cabinet and field studies were used to drive a leaf level model that integrates the responses of photosynthesis and respiration to changes in temperature and θ and incorporates acclimation using variable photosynthetic and respiratory parameters (Chapter 4). This model was used to estimate the annual canopy carbon exchange of the grass and kānuka in response to seasonal changes and to predict changes in canopy carbon exchange under varying future climate change scenarios. The model highlighted the importance of considering seasonally-acclimated parameters in estimating canopy carbon exchange of both plant types to concurrent changes in multiple environmental variables. The overall results support the conclusion that understanding the combined effects of environmental variables on canopy processes is essential for predicting canopy net carbon exchange of a pasture-shrub system in a changing global environment. It has been shown here that the rate of increase in photosynthesis with increasing θ is greater than that of respiration which results in a progressively greater apparent carbon gain at moderate values of θ. Moreover, the impact of lower values of θ, which reduced the apparent sensitivity of respiration to temperature, may effectively decrease the rate of respiration during warmer summer months and enhance thermal acclimation via downregulation of respiration. Therefore, considering the influence of soil water conditions on the temperature sensitivity of photosynthetic and respiratory model parameters has important implications for precisely predicting the net carbon exchange of a pasture-shrub system.

Barley protoplasts were shown to be a suitable experimental system for studies on the relative maximum during the decay of luminescence observed in most photosynthetic systems after excitation with far red light and in the presence of O2. The far red induced relative luminescence maximum was shown to be a result of three coinciding events: *Randomization of the S-states of the water splitting system during illumination with far red light. *Extreme oxidation of the PSII acceptor side after excitation with far red light and in the presence of O2. *Reverse coupling, causing partial re-reduction of the PSII acceptor side in the dark after far red illumination. When the CO2 concentration in the air above an intact barley leaf was lowered in the dark, the primary PSII acceptor QA was partially reduced. The effect was obtained by changes in CO2 over a wide concentration range including that of saturated photosynthesis. It was thus concluded that the effect was not related to the role of CO2 as the terminal electron acceptor in photosynthesis. White light induced relative maxima during the decay of luminescence frqm low CO2 adapted green algae were shown to be the result of either one or two interacting mechanisms: *Relaxation of qE quenching. *Dark reduction of QA occuring as a result of lowered internal Cj concentration in the dark. Far red induced luminescence decay kinetics and fluorescence induction kinetics, when analyzed with multivariat data analysis, were shown to contain information allowing prediction of the state of frost hardiness in artificially hardened seedlings of Scots pine. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1988, härtill 8 uppsatser.</p> / digitalisering@umu

Methods were developed to study delayed light emission (luminiscence) and fluorescence changes in intact leaves of plants. Delayed light emission, detected from plants in darkness, was used to produce images of the plant leaves. The procedure was termed "phytoluminography". The use of the method is suggested for dia- nostic purposes at early stages of disturbances of the leaf tissues, not detectable with the naked eye. The delayed light emission is associated with the photochemistry of photosystem II and the light induced conversion and storage of energy in the thylakoid membrane system of chloroplasts. Fluorescence yield changes were induced by lowering temperature between 20 C and -20 C. The temperature induced fluorescence changes in leaves parallel the temperature induced changes in isolated chloroplasts in reaction preparations mediating photosynthetic electron transport from endogenous water splitting to added NADP. At above freezing temperatures, lowering the temperature at a constant rate of 1 C per minute caused supressed electron transport and increased fluorescence yield which were linearely dependent on the temperature change in frost resistent plants. Repeated freeze-thaw cycles between 20 °C and -20 °C induced variable fluorescence yield changes which were gradually depleated to F0 or Fm when the electron transport was injuried on the oxidizing or on the reduzing side of photosystem II, respectively. The temperature induced fluorescence changes were used to characterize plants with different ability to withstand freezing temperatures. The method also discriminates between plants of different frost resistance, and the method was used in screening for frost tolerance. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1981, härtill 5 uppsatser.</p> / digitalisering@umu

Study of the Arabidopsis thaliana knockout mutant lacking Lhcb3 (koLhcb3) have revealed a close similarity to the wild type plants. Growth rate, NPQ, qP, Φ(PSII), circular dichroism spectra, pigment composition and content of LCHII trimers have been found to be unaffected by this mutation. The proteomic analysis shows only some minor increases in the amount of Lhcb1 and Lhcb2. PAM fluorometry revealed a significant increase in the rate of the state 1 to state 2 state transition in the koLhcb3. None the less, the extent of state transition is identical to wild type. Alterations in the PSII-LHCII supercomplex structure have been demonstrated as well. The M-trimer was found to be rotated ~21° CCW. This altered binding of the LHCII M-trimer is likely the cause of the altered affinity resulting in the increased rate of state transition. Proteomic analysis of the phosphorylation of LHCII revealed a significant increase in state 1 and 2 LHCII phosphorylation relative to wild type. Investigation whether phosphorylation or the altered LHCII binding is the cause of the accelerated rate of state transition have not been conclusive so far. A Lhcb6 depleted mutant (koLhcb6) showed a significant alteration of the PSII-LHCII supercomplex structure and photosynthetic acclimation processes. The LHCII M-trimer is depleted in the PSII-LHCII supercomplexes causing the state transition process to be “stuck” in state 2 and the mutants ability to preform NPQ is inhibited as well. The Lhcb6 protein was concluded to be essential for the binding of the LHCII M-trimer to the PSII core as well as energy transfer. The depletion of LHCII M-trimer was linked to the reduced ability to photoacclimate using NPQ as well.