Date of Award

2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Committee Chair

Leeland Cseke

Committee Member

Bruce Stallsmith

Committee Member

Kankshita Swaminathan

Subject(s)

Ectomycorrhizas., Plants--Nutrition--Molecular aspects., Fourier transform infrared spectroscopy.

Abstract

Plants form interactions with other symbiotic organisms such as mycorrhizal fungus and bacteria in the rhizosphere; therefore, it is pivotal to understand the nutrient exchange that takes place. In this experiment, Populus tremuloides seedlings were grown on a thin, nutrient dense media for the control as well a limited-nitrogen media. Fourier Transform Infrared Imaging is used in this study to analyze nitrate and ammonium concentrations in the rhizosphere of P. tremuloides with Laccaria bicolor and Pseudomonas fluorescens after 7 weeks of growth. Plants were grown on low-emission slides in the first experiment; however, due to media thickness issues, Polyethylene and CaF2 slides were chosen for the second experiment. Phenotypic results (root length, primary root branch number, leaf length, leaf number, and leaf color) on low-emission slides show nitrogen limitation inhibits plant growth and microbe interaction with exception of those grown with fungus. Plants grown on Polyethylene and CaF2 slides showed similar patterns as the low-emission variables; however, the growth was stunted in comparison. This data suggests P. tremuloides does not grow well on the Polyethylene slides. The FTIRI spectra collected indicated there is a high concentration of nitrate close to the base of the root while the ammonium concentration is quite low. The pattern of consumption and assimilation found suggests that ammonium is the preferred source of nitrogen to be consumed in the mycorrhizal fungus and plant system. In this research we also suggest that the mycorrhizal fungus, L. bicolor can assimilate 300% more nitrate than in the plant-only environment. Therefore, in the future, research should be done to develop more efficient fertilizers in order to maximize the nutrient benefits for beneficial fungi and soil microbes of crops; consequently, increasing soil health and decreasing fertilizer use.

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