Intra-trophic isotopic discrimination of N-15/N-14 for amino acids in autotrophs: Implications for nitrogen dynamics in ecological studies
| Autor: | Shawn A. Steffan, Yuko Takizawa, Naohiko Ohkouchi, Prarthana S. Dharampal, Yoshito Chikaraishi, Yoshinori Takano |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
0106 biological sciences
010504 meteorology & atmospheric sciences plant phenology Biology Photosynthesis 01 natural sciences trophic position winter dormancy Botany Autotroph Ecology Evolution Behavior and Systematics delta N-15 0105 earth and related environmental sciences Nature and Landscape Conservation Isotope analysis Trophic level Original Research chemistry.chemical_classification Ecology food web 010604 marine biology & hydrobiology fungi food and beverages Food web Isotopes of nitrogen Amino acid Chloroplast chemistry isotopic fractionation δ15N |
| Zdroj: | Ecology and Evolution |
| ISSN: | 2045-7758 |
| Popis: | The differential discrimination of nitrogen isotopes (N-15/N-14) within amino acids in consumers and their diets has been routinely used to estimate organismal tropic position (TP). Analogous isotopic discrimination can occur within plants, particularly in organs lacking chloroplasts. Such discrimination likely arises from the catabolic deamination of amino acids, resulting in a numerical elevation of estimated TP, within newly synthesized biomass. To investigate this phenomenon, we examined the 15N/14N of amino acids (delta N-15(AA)) in spring leaves and flowers from eight deciduous and two annual plants. These plants were classified on the basis of their time of bloom, plants that bloomed when their leaves were absent (Type I) versus plants that bloomed while leaves were already present (Type II). Based on the delta N-15(AA) values from leaves, both plant types occupied comparable and ecologically realistic mean TPs (= 1.0 +/- 0.1, mean +/- 1 sigma). However, the estimated TPs of flowers varied significantly Type I: 2.2 +/- 0.2; Type II: 1.0 +/- 0.1). We hypothesize that these results can be interpreted by the following sequence of events: (1) Type I floral biomass is synthesized in absence of active photosynthesis; (2) the catabolic deamination of amino acids in particular, leaves behind N-15 in the residual pool of amino acids; and (3) the incorporation of these N-15-enriched amino acids within the biomass of Type I flowers results in the numerical elevation of the TPs. In contrast, the actively photosynthesizing Type II leaves energetically sustain the synthesis of Type II flower biomass, precluding any reliance on catabolic deamination of amino acids. Amino acids within Type II flowers are therefore isotopically comparable to the Type II leaves. These findings demonstrate the idiosyncratic nature of the delta N-15(AA) values within autotrophic organs and have implications for interpreting trophic hierarchies using primary producers and their consumers. |
| Databáze: | OpenAIRE |
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