Journal Article

Contributions of leaf photosynthetic capacity, leaf angle and self-shading to the maximization of net photosynthesis in <i>Acer saccharum</i>: a modelling assessment

Juan M. Posada, Risto Sievänen, Christian Messier, Jari Perttunen, Eero Nikinmaa and Martin J. Lechowicz

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 110, issue 3, pages 731-741
Published in print August 2012 | ISSN: 0305-7364
Published online June 2012 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcs106
Contributions of leaf photosynthetic capacity, leaf angle and self-shading to the maximization of net photosynthesis in Acer saccharum: a modelling assessment

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  • Ecology and Conservation
  • Evolutionary Biology
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Background and Aims

Plants are expected to maximize their net photosynthetic gains and efficiently use available resources, but the fundamental principles governing trade-offs in suites of traits related to resource-use optimization remain uncertain. This study investigated whether Acer saccharum (sugar maple) saplings could maximize their net photosynthetic gains through a combination of crown structure and foliar characteristics that let all leaves maximize their photosynthetic light-use efficiency (ɛ).

Methods

A functional–structural model, LIGNUM, was used to simulate individuals of different leaf area index (LAIind) together with a genetic algorithm to find distributions of leaf angle (LA) and leaf photosynthetic capacity (Amax) that maximized net carbon gain at the whole-plant level. Saplings grown in either the open or in a forest gap were simulated with Amax either unconstrained or constrained to an upper value consistent with reported values for Amax in A. saccharum.

Key Results

It was found that total net photosynthetic gain was highest when whole-plant PPFD absorption and leaf ɛ were simultaneously maximized. Maximization of ɛ required simultaneous adjustments in LA and Amax along gradients of PPFD in the plants. When Amax was constrained to a maximum, plants growing in the open maximized their PPFD absorption but not ɛ because PPFD incident on leaves was higher than the PPFD at which ɛmax was attainable. Average leaf ɛ in constrained plants nonetheless improved with increasing LAIind because of an increase in self-shading.

Conclusions

It is concluded that there are selective pressures for plants to simultaneously maximize both PPFD absorption at the scale of the whole individual and ɛ at the scale of leaves, which requires a highly integrated response between LA, Amax and LAIind. The results also suggest that to maximize ɛ plants have evolved mechanisms that co-ordinate the LA and Amax of individual leaves with PPFD availability.

Keywords: Acer saccharum; sugar maple; canopy architecture; functional–structural modelling; LIGNUM; scaling; photosynthetic light-use efficiency; leaf Amax; leaf angle; nitrogen; resource use; optimization; plant evolution; plasticity; acclimation

Journal Article.  8266 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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