Atmospheric CO2 enrichment alters energy assimilation, investment and allocation in Xanthium strumarium |
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Authors: | Nagel Jennifer M Wang Xianzhong Lewis James D Fung Howard A Tissue David T Griffin Kevin L |
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Institution: | Department of Ecology and Evolutionary Biology, University of Tennessee, 1416 Circle Drive, Knoxville, TN 37996, USA. jnagel@utk.edu |
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Abstract: | Energy-use efficiency and energy assimilation, investment and allocation patterns are likely to influence plant growth responses to increasing atmospheric CO2 concentration (CO2]). Here, we describe the influence of elevated CO2] on energetic properties as a mechanism of growth responses in Xanthium strumarium. Individuals of X. strumarium were grown at ambient or elevated CO2] and harvested. Total biomass and energetic construction costs (CC) of leaves, stems, roots and fruits and percentage of total biomass and energy allocated to these components were determined. Photosynthetic energy-use efficiency (PEUE) was calculated as the ratio of total energy gained via photosynthetic activity (Atotal) to leaf CC. Elevated CO2] increased leaf Atotal, but decreased CC per unit mass of leaves and roots. Consequently, X. strumarium individuals produced more leaf and root biomass at elevated CO2] without increasing total energy investment in these structures (CCtotal). Whole-plant biomass was associated positively with PEUE. Whole-plant construction required 16.1% less energy than modeled whole-plant energy investment had CC not responded to increased CO2]. As a physiological mechanism affecting growth, altered energetic properties could positively influence productivity of X. strumarium, and potentially other species, at elevated CO2]. |
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Keywords: | allocation biomass construction cost (CC) elevated CO2 energy photosynthesis Xanthium strumarium (common cocklebur) |
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