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Abstract
The Bromeliaceae, a predominantly neotropical family, is well known for its biodiversity and adaptive strategies. Bromeliads play essential roles in ecosystems and hold economic significance in the horticultural and agricultural industries. Bromeliad species span a gradient from fully terrestrial to epiphytic, and some bromeliads have evolved specialized leaf tanks and absorptive trichomes to aid in water and mineral uptake. Early seedlings lack many of these features and may be more reliant upon roots for mineral acquisition than they will as adult plants. Nitrogen is a key and often highly limiting nutrient in many bromeliad habitats. This study examines the early growth responses of seedlings from four bromeliad species spanning the terrestrial to epiphyte gradient (Puya mirabilis, Aechmea recurvata, Billbergia brasiliensis, & Vriesea rafaelii) to three concentrations of nitrogen (0 vs. low- 0.01mM Urea vs. high- 1.00mM urea). I hypothesized that nitrogen application would stunt root growth and promote shoot growth in all but the most epiphytic species (V. rafaelii), and that the fully terrestrial species (P. mirabilis) would have the most sensitivity to differing nitrogen treatments. I germinated over 550 seeds per species and tracked their earliest growth and development for three weeks. I took data on the root & shoot lengths of all seedlings at weekly intervals, which were analyzed with ImageJ pixel analysis. A linear mixed-effect model revealed that high nitrogen application significantly inhibited root growth for three of the four species (A. recurvata, B. brasiliensis, P. mirabilis) at later developmental stages, supporting my hypothesis. Shoot growth increased but showed less consistent responses to nitrogen availability. This suggests either greater root system sensitivity to nitrogen or methodological limitations in shoot tissue measurement. Additionally, only P. mirabilis responded significantly to the low nitrogen treatment, supporting its greater hypothesized sensitivity to nitrogen as a terrestrial plant. Growth results for V. rafaelii under the different nitrogen treatments were not significant, potentially due to its slow life history strategy as a highly epiphytic bromeliad. Results also showed that high nitrogen treatment decreases the root to shoot ratio compared to other treatments, but remains consistent with species specific patterns of organ tissue investment over time. This study provides a foundation for understanding how bromeliad functional traits and life history strategies respond to nitrogen availability.