Thesis (doctoral)--University of Tartu, 2004. / Includes bibliographical references.

Thesis (M.S.)--Humboldt State University, 2009. / Includes bibliographical references (leaves 55-57). Also available via Humboldt Digital Scholar.

No description available.

Thesis (M.S.)--California Polytechnic State University, 2009. / Title from PDF title page; viewed on January 6, 2010. Major professor: Tryg Lundquist, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Civil and Environmental Engineering." "November 2009." Includes bibliographical references (p. 43-47).

A comprehensive field and laboratory study of nitrogen uptake in intertidal seaweeds was undertaken. Methods for measuring nitrogen uptake rates were evaluated. Short initial periods of rapid ammonium uptake were common in nitrogen deficient plants. The presence of ammonium inhibited nitrate uptake, but a certain degree of nitrogen starvation overcame this suppression. Laboratory studies with Porphyra perforata showed that nitrogen starved cultures maintained rapid initial ammonium uptake rates. The nitrate uptake system did not remain activated. Nitrogen starvation also resulted in a general decrease in soluble nitrogen content and a transient increase in nitrate reductase activity. The effectiveness of in vitro and in vivo nitrate reductase assays was investigated. The rate of nitrite production in the in vivo assay varied with incubation time. Therefore, the in vitro assay was used. Nitrate grown cultures of Porphyra perforata maintained high ammonium uptake rates. It was suggested that the rate of nitrate reduction was limiting the supply of nitrogen for further assimilation which may control ammonium uptake. Ammonium arid ammonium plus nitrate grown cultures had very low nitrogen uptake rates and nitrate reductase activities. Field studies with Gracilaria verrucosa confirmed that growth on ammonium inhibited nitrate uptake, nitrate accumulation and nitrate reductase activity. The presence of ammonium did not inhibit nitrate uptake rates in severely starved populations. All populations maintained high ammonium uptake rates suggesting that they were nitrogen limited at this time (August). Ammonium and nitrate uptake were saturable in the high intertidal G. verrucosa population but not in the low intertidal population. An investigation was made into the effect of nitrogen source and periodic exposure to air on growth, development and nitrogen uptake in Fucus distichus germlings. Gamete release, fertilization, germination and germling growth had no requirement for a specific form of nitrogen. Periodic exposure to air increased secondary rhizoid development. Ammonium and nitrate uptake rates of the germlings were much higher than for the mature thalli, but the affinity for nitrate was similar. The germlings showed saturable uptake kinetics but the mature thalli did not. The presence of ammonium inhibited nitrate uptake by the mature plants but not by the germlings. Mild desiccation enhanced nutrient uptake rates in several intertidal seaweeds. This uptake response occurred when growth was limited by that particular nutrient and when the thallus had been exposed to periodic desiccation for several weeks. The degree of enhancement, the percent desiccation producing maximum uptake rates and the tolerance to higher degrees of desiccation were related to intertidal location. This was shown to be an intraspecific as well as an interspecific adaptation. Transplant experiments with G. verrucosa showed that enhanced nutrient uptake rates after desiccation were related to intertidal height and not geographic location and that this response could be induced in approximately five weeks. It was suggested that this enhanced uptake response was an adaptation to nitrogen procurement and C/N homeostasis following periodic exposure when carbon was assimilated but when other nutrients were not available. / Science, Faculty of / Botany, Department of / Graduate

Nostoc commune UTEX 584 is a photosynthetic desiccation-tolerant cyanobacterium capable of fixing nitrogen. Biotinylated nifH and nifD gene probes from Azotobacter vinelandii (a gift from Dr. Dennis Dean) hybridized to nifH and nifD sequences isolated from Nostoc commune UTEX 584. This result supports the view that the nitrogenase structural proteins and their genes are highly conserved in nitrogen-fixing organisms (Rice et al., 1980). Southern transfers of genomic DNA prepared from N- commune UTEX 584 were digested with Hind III and hybridized with nifH-specific and nifD-specific probes. Multiple copies of nifH (three) and nifD (two) were detected. Using colony hybridization, a recombinant N- commune UTEX 584 genomic DNA-pBR322 plasmid library was screened with the biotinylated nifH-specific probe and positive hybridizing nifH clones were isolated. A restriction map of the 3.5 kb Hind III insert of the recombinant plasmid (pND001) was produced. From partial sequencing data it was possible to determine the positions of the N. commune UTEX 584 nifH and nifD genes within the cloned fragment and compare the partial nucleotide sequence and deduced amino acid sequences of the E- commune UTEX 584 nifHD genes with other organisms. Isolation of the nifH and nifD genes from Nostoc commune UTEX 584 now permits a more detailed study of nif gene expression in this desiccation-tolerant photosynthetic microorganism. / M.S.

Two separate greenhouse esperiments were conducted to determine the effects of additions of a blue-green algae (Nostoc muscorum) to nutrient solution cultures with different rates of nitrogen fertilizer on the growth of lettuce (Lactuca sativa L. cv. Buttercrunch). Lettuce yields increased with increased rates of N. Yields were significantly greater in treatments containing 165 ppm N with N. muscorum culture added (at the rate of 33.3% by volume) than in treatments containing the same rate of N without N. muscorum. A similar growth increase was not noted at lower N. muscorum inoculation rates (16.7% by volume). These preliminary data indicate the potential for increased yields of lettuce grown under specific conditions in nutrient culture. Further research of the complex interactions within this biological equilibrium are required before specific application recommendations may be suggested. / Master of Science

In recent history, C. jamaicense has been displaced by another native monocot, T. domingensis, predominantly resulting from increased phosphorous enrichment in the Everglades. This study aimed to elucidate these two species responses to low and high [Pi] in terms of allocation, photosynthate partitioning and growth. C. jamaicense growth was independent of Pi, while T. domingensis growth increased with [Pi]. Under high [Pi], allocation to younger T. domingensis shoots occurred, while C. jamaicense shoots retained more [Pi], while low [Pi] resulted in homogeneous allocation patterns for both species. Additionally, Pi deficiencies induced carbohydrate levels in older shoots of T. domingensis, while [Pi] had no effect on photosynthate partitioning patterns in C. jamaicense. ACP activity was induced by Pi deficiency in all T. domingensis shoots and increased with shoot age, while no effect was observed in C. jamaicense. Results indicate these two species differ in allocation strategies when [Pi] is altered. / by Brian Hill. / Vita. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.