Date of Award


Degree Type


Degree Name

Honors Thesis



First Advisor

Philip Villani


When exposed to stress, whether that be by pathogen, thermal or weather changes, or other components of the environment, plants employ a variety of defense mechanisms depending on the severity of the stress. When attacked by a pathogen, the moss Mnium cuspidatum utilizes an innate, basal response followed by hypersensitive response (HR) and systemic acquired resistance (SAR). Calcium is known to be involved in signaling cascades that mediate defense responses in other organisms. In the present study, lanthanum nitrate (LaNO3), methoxyerapamil (D600), and ethylene glycol tetraacetic acid (EGTA) were used to inhibit the presence of calcium in M. cuspidatum in the presence of the fungal pathogen Pythium irregulare in efforts to discover the relative involvement of calcium in innate immunity and HR. Results suggest that calcium in fact mediates signal transduction pathways utilized in such defense mechanisms. When grown on BCD medium containing these inhibitors and then subsequently infected with P. irregulare, the moss presented cleared-out leaves, browning stems, congregating chloroplasts, reactive oxygen species (ROS) production, and reinforcement of cell walls with the production and linking of polysaccharides—all events which are characteristic of innate basal response and HR.