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Periphyton are an important group of primary producers in stream ecosystems and are commonly used as indicators of water quality and ecosystem status. Periphyton biomass accumulation in streams is influenced by a number of factors, including nutrient supply, shading by riparian vegetation, substrate properties, and hydrological conditions. Urban land use potentially influences all of these factors in ways that may promote or constrain periphyton growth. Such influences may be further altered by efforts to restore urban streams within parks and residential settings. To test this, I compared patterns of stream periphyton biomass among rural (forested), urban, and restored urban streams within and around Umeå. I found that periphyton biomass varied up to 50-fold among sites but did not differ significantly among stream classes (i.e., rural vs. urban vs. urban restored). Periphyton biomass did tend to increase among sites with greater nutrient concentrations and warmer temperature. Yet, these patterns were influenced by substrate conditions within and among streams, with significantly greater biomass observed on larger cobbles when compared to sand. Results indicate that sedimentation in the studied urban streams (and likely in streams in general) may restrict algal growth, even if other conditions are otherwise favourable. Conversely, urban restoration involving the placement of course substrate on the stream bottom may enhance algal growth locally, particularly where light and nutrients are both elevated. My findings illustrate that periphyton biomass depends on a multi-scale framework of factors that should be considered when managing streams, especially in urban areas where streams are often influenced by both local and catchment-scale stressors.

The effectiveness of titanium dioxide (TiO?) in polyethylene films at preventing the photooxidation of riboflavin in a model solution was evaluated. Five different TiO? loads (0.5-8.0 wt%), each at 3 different thicknesses (50-100 um) were evaluated. A photochemical reactor, equipped with a 350W mercury lamp, provided full spectrum light or narrow bandwidth wavelength exposure, using filters allowing transmission at 25 nm wavebands at maximum peak height at 450, 550, or 650 nm. Riboflavin concentration was measured by HPLC over 8 hours of exposure. Increased TiO? load and thickness significantly affected riboflavin photooxidation (p<0.05). TiO? load had more influence on protection provided to riboflavin than did film thickness. Film opacity correlated linearly with decreased photooxidation (R2 of 0.831 & 0.783 for full spectrum and 450 nm bandpass-filter sets, respectively). Riboflavin photooxidation proceeded most rapidly with the full spectrum exposure (light intensity 118 ° 17.3 mW). Photooxidation occurred in the 450 nm bandpass-filter, but not for 550 & 650 nm sets (light intensities of 2.84 °0.416, 3.36 °0.710, and 0.553 ° 0.246 mW, respectively). Effect of fluorescent light-exposure (2020-1690 lux) on the same system was monitored over 2 days. Riboflavin degradation in the photoreactor proceeded ~300 times faster than under fluorescent lighting. Riboflavin degradation was found to significantly increase with the addition of chlorophyll-like tetrapyrroles (p<0.05). Riboflavin was found to significantly decrease the degradation rate of the tetrapyrroles pyropheophytin a and pheophytin a (p<0.05). The decrease in rate was not significant for chlorophyll a (p>0.05). / Master of Science in Life Sciences

The stage of maturity of seeds at harvest is an important factor that determines seed vigor. Separating seeds from a seed lot composed of many different stages of development can be difficult especially after maximum dry mass is attained. Separating seeds based on their physiological maturity is more challenging than sorting seeds based on their physical properties. Seeds may be non-destructively sorted using chlorophyll fluorescence (CF) as a marker of seed maturity. This study was conducted to test whether CF could be used to remove low vigor immature seeds from muskmelon (Cucumis melo L.'Top Mark') and tomato (Lycopersicum esculentum) seed lots. Light treatments were applied to determine whether the light environment during seed harvesting and processing could affect chlorophyll content and seed vigor. Seeds from nine stages of development were collected from 'TopMark'. Seeds from three stages of fruit development (red ripe, breaker, and mature green) were harvested from tomato cultivar Money Maker and two phytochrome mutants: phytochrome A mutant, fri-1 and phytochrome B mutant, tri-1. The SeedMaster Analyzer (Satake USA Inc., Houston Texas) was used to measure CF and to sort individual seeds according to CF levels. Immature tomato seeds and muskmelon, harvested from green fruits, had the highest CF (p>0.001). Contrary to the results obtained with the other tomato genotypes, the vigor of tri-1 did not change inversely with changing CF levels, rather, seeds with low CF had the same vigor as seeds with high CF. This result may suggest that the presence of phytochrome B exerts an inhibitory influence on vigor in tomato seeds, and that the persistent presence of chlorophyll during seed development does not affect vigor. The light treatments had no consistent effect on seed chlorophyll content or on vigor in either tomato or muskmelon. / Master of Science

Mesotrione is under evaluation for registration in turfgrass for weed control, but often requires repeat treatments. Previous research in agricultural crops indicates tank mixtures with mesotrione may improve weed control. Three field trials were conducted in 2005 and 2006 in Blacksburg, VA on smooth crabgrass in perennial ryegrass and tall fescue. Data indicate mesotrione applied in combination with bentazon, bromoxynil, or carfentrazone, controlled smooth crabgrass better than any of these herbicides applied alone at all sites. Adding mesotrione to MSMA and quinclorac improved smooth crabgrass on of three sites. Sequential mesotrione applications improved long term weed control. / Master of Science

In oxygenic phototrophs, the photosynthetic machinery is located in thylakoid membrane (TM), a specialized endogenous membrane system. How TM are synthesized remains however mostly unknown. The aim of this thesis was to clarify a link between the synthesis of chlorophyll (Chl)-binding proteins, the main protein component of TM, and the formation of TM system in the model cyanobacterium Synechocystis PCC 6803. During the project, the analysis of TM under various growth conditions and in Chl-deficient mutants has demonstrated that a sufficient amount of de novo produced Chl molecules is crucial for the TM biogenesis. Particularly, the synthesis of the photosystem II subunit CP47 and trimeric photosystem I appeared to be sensitive to a shortage in de novo made Chl molecules. Interestingly, a specialized ribosome-binding protein (Pam68) has been identified to facilitate the insertion of Chl molecules into CP47. The synthesis of Chl-proteins and the biogenesis of TM have been further explored in cells recovering from long-term nitrogen depletion. Using this approach, it was possible to identify a large structure in the cell cytosol, which is very likely the site of TM biogenesis, and to correlate the appearance of this structure with the restored biogenesis of Chl-binding proteins.

Chlorophyll and solanine syntheses as influenced by cultivars, specific gravities, light intensities, and duration of exposure to light were studied in potato (Solanum tuberosum, L.) tubers. Chemicals, gamma radiation, clear polyethylene packaging in 15 per cent co 2 , and storage at subatmospheric pressure were employed to control the formation of these two compounds. The toxicity of solanine to mice, the fungus Trichoderma viride, and cholinesterase inhibition patterns in rabbits and a dog were evaluated. The influence of the central nervous system stimulating drugs was investigated to find if they counteracted solanine toxicity. Of the 11 cultivars tested, tubers of Bounty, Kennebec, Nor chip, and Red Lasoda were most sensitive to greening and solanine development. LaChipper and Platte tubers were least susceptible to greening and their solanine contents were minimum. The significant differences in chlorophyll and solanine formation among cultivars showed that greening potential is a cultivar characteristic. xi Chlorophyll development in tubers was inversely related to their specific gravity. Solanine synthesis was, however, not dependent on specific gravity. Studies on effect of four light intensities on Kennebec potato tubers that were stored for nearly 6 months showed that more chlorophyll formed at 100 and 150 ft-c than at 50 and 200 ft-c light intensities. Generally, chlorophyll formation increased with increased light intensity up to 100 ft-c, slowly and steadily declined up to 150 ft-c, and sharply declined at 200 ft-c. There were no significant differences in the solanine contents of the tubers after exposure to these light intensities. The duration of exposure of the tubers to 100 ft-c revealed that solanine and chlorophyll contents increased linearly with the duration of exposure up to the sixth and tenth day, respectively. There was no difference in the amount of chlorophyll formed at the end of the tenth and fifteenth day. The solanine contents were rather constant from the sixth to the tenth day and then slightly declined at the end of the fifteenth day. The respiration of the tubers did not seem to have an apparent relationship to solanine and chlorophyll formation. Investigation on the control of greening showed that two chemicals, Ethrel (2-chloroethylphosphonic acid) and Alar (succinamic acid, 2, 2-dimethylhydrazide) when applied at 10, 000 ppm by vacuum injection technique, were significantly effective in inhibiting chlorophyll and solanine syntheses. Ethrel was most effective in controlling the chlorophyll formation and the least solanine xii was formed after the Alar treatment. The dose of 10 krads of gamma radiation inhibited 80 per cent, while polyethylene packaging with 15 per cent co 2 , only 32 per cent of chlorophyll synthesis. Storage of tubers at subatmospheric pressure of 126 mm-Hg resulted in complete inhibition of chlorophyll formation. The irradiation, co 2 environment either alone or in combination, and subatmospheric pressure treatments did not affect solanine synthesis. Solanine was toxic to mice, rabbits, a dog, and the fungus Trichoderma viride. The LD 50 for intraperitoneal (ip) administration, single dose, in mice was 32. 3 mg of solanine per Kg body weight, the 19/20 confidence limits being 27. 6 - 37. 9 mg. Plasma and erythrocytic cholinesterase inhibition in rabbits indicated that solanine was a weak to moderate inhibitor of both specific and nonspecific cholinesterase. There was less inhibition of erythrocytic cholinesterase than that of plasma in vivo. In an anesthetized dog, cumulative doses of solanine showed a quick inhibition of cholinesterase but rapid recovery · was noted in the case of serum enzyme, while there was no inhibition of the red cell enzyme. A prior intraperitoneal dose of 2 mg/Kg of atropine sulfate lowered the mortality after ip injection into mice at 40 mg/Kg of solanine from 9/10 to 5/10. Similar application of pargyline (5 mg/Kg ip) and amphetamine (5 mg/Kg ip) had no effect on mortality from solanine. Atropine influence appeared antagonistic and counteracted solanine toxicity. The concentration of 10 mg of solanine per 100 ml of potato-dextroseagar medium had no effect on the Trichoderma viride fungus growth, while at a concentration of 200 mg, the growth ceased. The (Lethal Concentration) Lc 50 was 102. 2 mg/100 ml, and 19/20 confidence limits being 83. 85 - 124. 6 mg.

<p>The chlorophyll a/b binding (CAB) genes play a very central role in all photosynthetic systems and are for Avena sativa (oat) totally unexplored. This dissertation investigates a large number of EST sequences and this investigation characterises the CAB genes in oat, with help from the evolutionary background of oat and the comparison to a reference organism and similar species.</p>