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In the modern era, maize has become the most successful crop grown in the United States. According to the USDA over 90 million acres of land are planted to corn and 96.2% of the U.S feed grain production is made up of the cereal. Part of the success of maize is due to its floral architecture, and its pollination technique in which the flower opens, exposing stamens containing pollen into the air. A unique organ called the lodicule functions as a release mechanism, forcing the flower to open. Lodicules from grasses and eudicot petals are homologous, yet there is little known of how lodicules are specified during development. Other examples of maize mutants with defects in the lodicule have been discovered including silky1, bearded ear, and sterile tassel silky ear1, but there has been no definitive pathway found that specifies the developmental characteristics of the lodicule. My work has focused on a maize mutant, tasselsheath3 (tsh3), which displays a floral phenotype in the lodicule whorl to better understand this organ. Analysis of tsh3 was separated into two sections: a quantitative phenotypic analysis of the tsh3 floral mutant phenotype, compared to a previously unstudied floral phenotype of tasselsheath1 (tsh1), as well as a tsh1; tsh3 double mutant. I found that lodicule morphology and lodicule number was affected in tsh1, tsh3, and the tsh1; tsh3 mutants. Section two was to identify the single gene that was disrupted in tsh3 mutants. Through both fine mapping and next generation sequencing I was able to localize tsh3 to a region between 148.1mbp and 152.8mbp on chromosome 6. This 4.7mbp region of interest contains 64 protein coding genes. As evidenced by the phenotyping data, tsh3 plays a role specifying lodicule identity during development and has been localized to this region of chromosome 6 on the maize genome.

Iron is among the essential micronutrients for all living organisms and is a cofactor for many cellular redox reactions. Although iron is a highly abundant metal element found in the earth’s crust, it is also a limiting factor in plant development when it is present as insoluble ferric oxides. Plants have evolved two strategies to acquire soluble iron referred to as Strategy I and Strategy II. Our lab has focused on the Arabidopsis thaliana double mutant ysl1ysl3. The mutants display a chlorotic phenotype and are unable to correctly respond to iron deficiency. Grafting is a common method for joining different plant tissues and has been used for studies of long distance signaling. Past studies of iron signaling in Arabidopsis have not been able to provide a mechanism for how plants are able to signal the iron status of the shoot, where iron demand is high, to roots, where iron uptake occurs. The iron signaling experiments included in this thesis follow a seedling-graft approach to understand if grafts are capable of properly sensing iron. A longstanding question of iron homeostasis in plants is the identity of the iron sensors in plants. It was hypothesized that YSL1 and YSL3 have both a transporter function and a receptor function, and therefore function as transceptors. In our predicted model it was proposed that YSL1 and/or YSL3 are directly involved in iron status signaling either in perception and/or transmission of the signal. As evidenced through seedling grafting experiments here, YSLs play a critical part of long distance signaling that plant shoots use to signal their iron status to the roots. In this thesis, YSL1 and YSL3 are shown to be required in the shoots in order for signaling to occur correctly in the roots. To facilitate the analysis of gene expression in the grafts, a FRO3promoter:GUS construct was used in the Col-O WT background. The FRO3 promoter was selected because it is expressed in both leaves and roots under iron deficiency. Experiments showed that the genotype of the shoot used in the grafts is critical for Fe-deficiency induced gene expression in the roots. Thus, grafting has revealed that root iron deficiency responses require YSL1 and YSL3 in leaves for signal transmission. This directly links them to long-distance signaling, and supports the idea that these proteins could be acting as transceptors.

Carnivorous plants face significant conservation challenges due to habitat destruction, climate change, and illegal harvesting. This study explores how elevation and population size influence key-life history traits of D. rotundifolia, such as flowering phenology, prey capture efficiency, seed production, and germination rates. Higher elevations and larger populations are associated with extended flowering durations and increased prey capture. However, seed production and germination rates show complex patterns that are likely influenced by genetic diversity, resource availability, or environmental conditions. These insights inform targeted conservation strategies, emphasizing habitat preservation, enhancing prey availability, and maintaining genetic diversity. Public education and community engagement are also crucial for reducing human disturbances. This research contributes to the broader understanding of carnivorous plant ecology, supporting effective conservation measures to protect D. rotundifolia and its ecosystems.

The occurrence of weed species with hemp significantly affects the development and yield of hemp (Cannabis sativa L.). Three experimental studies were conducted to examine whether weed species like Amaranthus tuberculatus L., Eleusine indica L., Ipomoea spp. L. suppress the growth of hemp. The results show that the presence of these weed species was responsible for the reduced growth of hemp in terms of height, stem diameter number of leaves except when some weed densities were reduced with a grass-specific herbicide, but the weed species did not have any association with the N (nitrogen) and C (carbon) assimilation of hemp. Additionally, utilizing a de Wit replacement series design, a greenhouse study investigated the competitiveness of the two hemp cultivars ‘Jin Ma’ and ‘NWG’ and three weed species i.e., A. tuberculatus, Glycine max L., and Setaria faberi L. to see how they affect each other through both intra- and interspecific competition. The outcome demonstrated that the weed species were responsible for the loss of yield as well as suppressing the growth of hemp. However, there were some mixtures where the plants were overyielding as well as the effects of two different hemp cultivars varied in response to the three weed species. Moreover, the effect of the three weed species was different based on hemp cultivars and mixture. These two studies suggest that controlling the weedy species in hemp fields is important to reduce the loss of hemp yield. Additionally, another separate greenhouse study looked at the accumulation of Trigonelline (TRG) in the leaves of two hemp cultivars ‘Jin Ma’ and ‘NWG’. The finding of this experiment demonstrates that the amount of TRG varies between when the plants grow under control and drought stress treatment. However, the two cultivars did not vary in terms of TRG accumulation. The three experimental studies showed that weeds have a significant effect on hemp growth parameters, and the accumulation of trigonelline varies based on drought conditions.

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No description available.

<p>Like other eukaryotic cells, plant cells contain an endomembrane system composed of compartmentalized organelles with specialized functions. Vesicle trafficking mediates the transport of materials between different organelles and between cells and the environment. The vesicle trafficking process is highly dynamic and plays essential roles in maintaining cellular homeostasis and environmental adaptation. Because of the essential roles of vesicle trafficking in plant growth and development, genes that are involved in vesicle trafficking often have redundant function when they exist as a large family or cause embryonic lethality when they exist as a signal gene or small gene family. Chemical genetics uses small molecule inhibitors to affect protein function without interfering with plant’s genome. Bioactive small molecules can generate a temporary perturbation of a biological system in a reversible and dose-dependent fashion, which allow us to observe dynamic cellular processes and discover new components in trafficking machineries. We recently discovered two small molecules named Endosidin2 (ES2) and Endosidin20 (ES20) that disrupt vesicle trafficking in plants. ES2 inhibits exocytosis by targeting the EXO70A1 subunit of the exocyst complex in plant cells. ES20 targets cellulose synthase (CESA) at the catalytic site and inhibits the delivery of Cellulose Synthase Complex (CSC) to the plasma membrane. This research thesis aims to characterize the specificity of ES2 on EXO70 homologs and identify new genes that mediate CSC trafficking. Drug Affinity Responsive Target Stability (DARTS) assay was used to test the specificity of ES2 in targeting different EXO70s in Arabidopsis. Chemical genetic screen for mutants that have increased sensitivity was conducted to identify novel genes related to CSC trafficking. This project provides new insights in the specificity of ES2 in targeting different EXO70s in plants and the regulatory mechanisms of CSC trafficking that control plant cellulose synthesis.</p><p><br></p>

Master of Science / Department of Biology / Carolyn J. Ferguson / The genus Phlox L. presents intriguing opportunities for systematics research, and P. nana is of particular interest. Phlox nana occurs chiefly in mountains of the Chihuahuan desert to northern New Mexico, and it exhibits much morphological variation across its range. Historically, this taxon has been recognized as a single species (sometimes with infraspecific taxa), or as several species. Perhaps most interesting, variation in ploidy level (cytotypic variation) has been evidenced for P. nana. This research employed flow cytometry methods in conjunction with chromosome counts to document patterns of cytotypic variation. Intensive fieldwork in Arizona, New Mexico and Texas enabled excellent sampling, and evaluation of ploidy level for 76 populations was achieved. Diploid and tetraploid chromosome counts were made (four diploid counts; five tetraploid counts), and flow cytometry was conducted on all populations, providing evidence for diploid, tetraploid and hexaploid populations. Polyploids were found to occur in many geographical areas, and in some regions, diploids and polyploids occur in close geographical proximity (e.g., within both the Davis Mountains and the Chisos Mountains of west Texas). Genome size data are presented (with discussion of unusual populations), and geographic patterns of cytotypic variation are presented and discussed. Patterns are also briefly considered with respect to morphology and taxonomy: cytotypic variation does not readily align with historical recognition of taxonomic variation, and this work sets the stage for ongoing, detailed morphometric study. Research on particular species of Phlox benefits from an understanding of a broad phylogenetic context, and low copy nuclear DNA regions are an important resource for phylogeny development. This research further evaluated part of the NADP-dependent isocitrate dehydrogenase gene (idhB) for its usefulness in inferring relationships in Phlox. Samples were PCR amplified for idhB and cloned, and resulting sequences were added to a larger set of idhB sequence data previously developed in the lab. A total of 163 samples were included, and Bayesian Inference and Maximum Parsimony analyses were conducted for complete data sets. Phylogenetic findings are discussed in light of previous work based on chloroplast and high copy nuclear DNA regions, and challenges and utility of using idhB are discussed.