Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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2006 - 200912010 - 20151

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    Elevated Temperature Effects on Carotenoid Biosynthesis in the Diploid Strawberry, Fragaria vesca
    (2015) Jackson, Melantha E.; Sintim, Herman; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Carotenoids, a subfamily of the isoprenoids, are one of the most diverse classes of secondary metabolites distributed throughout nature. They are lipophilic in nature, and include over 600 tetraterpenoid compounds synthesized by plants, bacteria, and fungi. Carotenoids, as the major pigment responsible for the red, yellow, and orange colors of fruits and vegetable, help promote human health and wellness by serving as antioxidants and precursors to vitamin A. Climate changes that threaten plant reproduction, negatively impact crop production worldwide. Little is understood about the chemistry of carotenoids in plant reproductive structures. Insight into the metabolic roles and functions of carotenoids in plant reproduction and, the effects of abiotic stresses on carotenoid biosynthesis in these structures would globally impact agriculture production by reducing yield loss. The potential for these metabolites to protect the reproductive structures under elevated temperature stress was assessed using biochemical analysis, genomics, and genetic studies. Fourteen candidate genes involved in carotenoid biosynthesis were identified, revealing three small gene families. Quantitative real-time polymerase chain reaction (qPCR) expression analysis of these genes and targeted metabolic profiling using liquid chromatography-high resolution mass spectrometry (LC-HRMS) throughout plant development under control and moderately elevated temperature stress showed that gene expression and metabolite accumulation are tissue specific and differentially responsive to elevated temperature stress. Three phytoene synthase genes were identified and characterized. Genomic analyses revealed that the PSY gene family exhibits functional diversity in plant tissues, both with respect to location and stage of development, as well as in response to abiotic stress.
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    Effects of Post-harvest Treatment and Heat Stress on the Antioxidant Properties of Wheat
    (2006-08-03) Su, Lan; Yu, Liangli; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This research examined and compared grain, bran, and micronized bran samples of Ankor and Trego wheat stored at 25, 60 and 100oC for their free radical scavenging properties, total phenolic content (TPC) and phenolic acid compositions. Bran and micronized bran samples stored at 100oC showed decreased TPC and free radical scavenging activities over 9 days of treatment, while there was no significant change observed for grain samples. Because of smaller particle size, micronized bran was more sensitive to heat stress when compared to bran at the two elevated temperatures. In addition, extractable phenolic acids were increased during storage for all kinds of samples on a per dry weight basis. These results demonstrate that whole grain is a preferred form of long-term storage for better antioxidant preservation, and reducing particle size may accelerate the loss of natural antioxidants in wheat bran during storage and heat treatment.