EAGER: RUI: The Physiology and Nitrogen Assimilatory Pathway of Spanish Moss (Tillandsia Usneoides) in Pesponse to Increased Nitrogen

Spanish moss (Tillandsia usneoides) is a slow-growing rootless plant in the Southeastern United States that is often found on trees, such as live oak. Since they don’t have roots in the soil, these “air plants” must acquire nutrients from the atmosphere and from rainfall. Therefore, their environment is extremely nutrient poor compared to other plants.

This project investigates how Spanish moss responds to increased amounts of nitrogen, the nutrient that most often restricts plant growth. Nitrogen content in Spanish moss is remarkably lower compared to other plants, which presents a botanical mystery: how does Spanish moss survive in an environment where nitrogen is so scarce? Experiments are designed to determine if Spanish moss is truly nitrogen-limited or rather if these plants have evolved a unique ability to efficiently use limited nitrogen.

Understanding how Spanish moss survives despite limited nitrogen could provide insight to plant breeders who seek to improve crop yield on marginalized soils. Additionally, because climate change is predicted to increase atmospheric deposition of nitrogen, these experiments might reveal future growth patterns of Spanish moss. The study includes training of undergraduates from Coastal Carolina University and the National Technical Institute for the Deaf in modern scientific techniques, enhancing their education and the diversity of the future scientific workforce.

The central goal of this hypothesis-driven project is to provide evidence if increased nitrogen availability supports enhanced growth of the epiphyte Spanish moss by stimulating the nitrogen assimilation pathway. Biochemical, metabolomic, and physiological approaches will be used to answer two key questions: (i) does Spanish moss display nitrogen luxury consumption and (ii) are these plants nitrogen limited or rather do they display high nitrogen use efficiency?

The project will manipulate nitrate and ammonium inputs by both spiking and treating with a physiologically relevant concentrations. The response of the nitrogen assimilation pathway will be assessed by measuring nitrate reductase and glutamine synthetase activity, amino acid and protein concentration, and amino acid biosynthesis. Importantly it will determine if increased flux of inorganic nitrogen into de novo amino acids is coupled with growth.

Additionally, experiments will measure the kinetics of nitrate reductase- a rate limiting enzyme in plant nitrogen assimilation- and determine how it is regulated by nitrate and ammonium availability. Spanish moss is tightly tied to southern culture and identity, yet nothing is known about how they metabolize nitrogen. This project will be the first to investigate nitrogen metabolism in these plants, and to determine if increased nitrogen availability and assimilation is coupled to growth.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.