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Original Research ARTICLE

Front. Plant Sci., 04 February 2014 | http://dx.doi.org/10.3389/fpls.2014.00012

The effect of irradiance on the carbon balance and tissue characteristics of five herbaceous species differing in shade-tolerance

  • 1Plant Ecophysiology, Institute of Environmental Sciences, Utrecht University, Utrecht, Netherlands
  • 2IBG-2 Plant Sciences, Forschungszentrum Jülich GmbH, Jülich, Germany

The carbon balance is defined here as the partitioning of daily whole-plant gross CO2 assimilation (A) in C available for growth and C required for respiration (R). A scales positively with growth irradiance and there is evidence for an irradiance dependence of R as well. Here we ask if R as a fraction of A is also irradiance dependent, whether there are systematic differences in C-balance between shade-tolerant and shade-intolerant species, and what the causes could be. Growth, gas exchange, chemical composition and leaf structure were analyzed for two shade-tolerant and three shade-intolerant herbaceous species that were hydroponically grown in a growth room at five irradiances from 20 μmol m−2 s−1 (1.2 mol m−2 day−1) to 500 μmol m−2 s−1 (30 mol m−2 day−1). Growth analysis showed little difference between species in unit leaf rate (dry mass increase per unit leaf area) at low irradiance, but lower rates for the shade-tolerant species at high irradiance, mainly as a result of their lower light-saturated rate of photosynthesis. This resulted in lower relative growth rates in these conditions. Daily whole-plant R scaled with A in a very tight manner, giving a remarkably constant R/A ratio of around 0.3 for all but the lowest irradiance. Although some shade-intolerant species showed tendencies toward a higher R/A and inefficiencies in terms of carbon and nitrogen investment in their leaves, no conclusive evidence was found for systematic differences in C-balance between the shade-tolerant and intolerant species at the lowest irradiance. Leaf tissue of the shade-tolerant species was characterized by high dry matter percentages, C-concentration and construction costs, which could be associated with a better defense in shade environments where leaf longevity matters. We conclude that shade-intolerant species have a competitive advantage at high irradiance due to superior potential growth rates, but that shade-tolerance is not necessarily associated with a better C-balance at low irradiance. Under those conditions tolerance to other stresses is probably more important for the performance of shade-tolerant species.

Keywords: construction costs, growth analysis, photosynthesis, root respiration, scaling slope analysis, shoot respiration, whole-plant gas exchange

Citation: Pons TL and Poorter H (2014) The effect of irradiance on the carbon balance and tissue characteristics of five herbaceous species differing in shade-tolerance. Front. Plant Sci. 5:12. doi: 10.3389/fpls.2014.00012

Received: 02 October 2013; Accepted: 08 January 2013;
Published online: 04 February 2014.

Edited by:

Bertrand Muller, Institut National de la Recherche Agronomique, France

Reviewed by:

Dirk Vanderklein, Montclair State University, USA
Cristina Nabais, University of Coimbra, Portugal

Copyright © 2014 Pons and Poorter. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Thijs L. Pons, Plant Ecophysiology, Institute of Environmental Sciences, Utrecht University, Padualaan 8, 3508 CH Utrecht, Netherlands e-mail: t.l.pons@uu.nl