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Abstract Detail

Pteridological Section/AFS

Watkins, Jr., James (Eddie) [1], Mack, Michelle C. [2].

δ15N Natural abundance and nitrogen use of tropical fern gametophytes and sporophytes.

A central goal of plant ecology is to develop a mechanistic understanding of species distributions in both space and time. In N-limited systems or in systems where N-availability is heterogeneous, plants either compete directly for N or avoid competition via resource partitioning. The partitioning and uptake of different chemical forms of N is receiving increased attention due to the revelation that plants can circumvent microbial mineralization of N and directly uptake organic N in the form of amino acids. The goal of this work is to determine if tropical fern species differ in their ability to take up different forms of nitrogen in both the gametophyte and sporophyte generations. This will be linked to the natural abundance of δ15N from field collected individuals to determine if species access different nitrogen pools. Results from the uptake studies indicate that ferns show preference for specific N forms and that they do so differently in sporophyte and gametophyte generations. In the the epiphytic Campyloneurum brevifolium, both gametophytes and sporophtyes exhibited high potential for uptake of amino acid N followed by inorganic NH4+. Uptake potentials shifted in the gametophytes of the terrestrial Danaea wendlandii with uptake of amino acids and NH4+ essentially equal. When compared across several taxa and generations, δ15N signatures varied widely. In most cases, gametophytes were significantly depleted. The observed differences in foliar δ15N values and evidence of differential uptake of N forms indicate that ferns can partition N by form. The preference of N form varied with greater preference on organic N in the epiphytic vs. terrestrial species and between gametophytes and sporophtyes. These data indicate that there are different nutrient use strategies between the two life forms and between generations. Individuals that can circumvent mineralization in the N cycle by direct amino acid uptake may have a tremendous competitive advantage relative to those relying on inorganic forms.

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1 - Colgate University, Biology, 13 Oak Drive, Hamilton, NY, 13346, USA
2 - University of Florida, Department of Botany, 220 Bartram Hall, P.O. Box 118526, Gainesville, Florida, 32611-8526, USA

uptake kinetics
resource competition
community assembly.

Presentation Type: Oral Paper:Papers for Sections
Session: 2
Location: 556B/Convention Center
Date: Monday, August 2nd, 2010
Time: 8:45 AM
Number: 2004
Abstract ID:778

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