Journal Article

On the complementary relationship between marginal nitrogen and water-use efficiencies among <i>Pinus taeda</i> leaves grown under ambient and CO<sub>2</sub>-enriched environments

Sari Palmroth, Gabriel G. Katul, Chris A. Maier, Eric Ward, Stefano Manzoni and Giulia Vico

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 111, issue 3, pages 467-477
Published in print March 2013 | ISSN: 0305-7364
Published online January 2013 | e-ISSN: 1095-8290 | DOI:
On the complementary relationship between marginal nitrogen and water-use efficiencies among Pinus taeda leaves grown under ambient and CO2-enriched environments

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Background and Aims

Water and nitrogen (N) are two limiting resources for biomass production of terrestrial vegetation. Water losses in transpiration (E) can be decreased by reducing leaf stomatal conductance (gs) at the expense of lowering CO2 uptake (A), resulting in increased water-use efficiency. However, with more N available, higher allocation of N to photosynthetic proteins improves A so that N-use efficiency is reduced when gs declines. Hence, a trade-off is expected between these two resource-use efficiencies. In this study it is hypothesized that when foliar concentration (N) varies on time scales much longer than gs, an explicit complementary relationship between the marginal water- and N-use efficiency emerges. Furthermore, a shift in this relationship is anticipated with increasing atmospheric CO2 concentration (ca).


Optimization theory is employed to quantify interactions between resource-use efficiencies under elevated ca and soil N amendments. The analyses are based on marginal water- and N-use efficiencies, λ = (∂A/∂gs)/(∂E/∂gs) and η = ∂A/∂N, respectively. The relationship between the two efficiencies and related variation in intercellular CO2 concentration (ci) were examined using A/ci curves and foliar N measured on Pinus taeda needles collected at various canopy locations at the Duke Forest Free Air CO2 Enrichment experiment (North Carolina, USA).

Key Results

Optimality theory allowed the definition of a novel, explicit relationship between two intrinsic leaf-scale properties where η is complementary to the square-root of λ. The data support the model predictions that elevated ca increased η and λ, and at given ca and needle age-class, the two quantities varied among needles in an approximately complementary manner.


The derived analytical expressions can be employed in scaling-up carbon, water and N fluxes from leaf to ecosystem, but also to derive transpiration estimates from those of η, and assist in predicting how increasing ca influences ecosystem water use.

Keywords: Elevated CO2; FACE; fertilization; leaf gas exchange; nitrogen; optimal stomatal conductance; pine; Pinus taeda; water-use efficiency

Journal Article.  7717 words.  Illustrated.

Subjects: Plant Ecology ; Plant Physiology

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