Structural and Functional Variability within the Canopy and its Relevance for Carbon Gain and Stress Avoidance

Authors

Christiane Werner, Universidade Lisboa, Portugal
Ronald J. Ryel, Utah State UniversityFollow
Otilla Correia, Universidade Lisboa, Portugal
Wolfram Beyschlag, Universitat Bielefeld, Germany

Document Type

Article

Journal/Book Title/Conference

Acta Oecologica

Volume

22

Issue

2

Publisher

Elsevier

Publication Date

2001

First Page

129

Last Page

138

Abstract

The functional variability in leaf angle distribution within the canopy was analysed with respect to regulation of light interception and photoprotection. Leaf orientation strongly determined the maximum photochemical efficiency of PSII (Fv/Fm) during summer: horizontal leaves were highly photoinhibited whereas vertical leaf orientation protected the leaves from severe photoinhibition. The importance of leaf orientation within the canopy was analysed in two Mediterranean macchia species with distinct strategies for drought and photoinhibition avoidance during summer. The semi-deciduous species (Cistus monspeliensis) exhibited strong seasonal but minimal spatial variability in leaf orientation. Reversible structural regulation of light interception by vertical leaf orientation during summer protected the leaves from severe photoinhibition. The evergreen sclerophyll (Quercus coccifera) exhibited high spatial variability in leaf angle distribution throughout the year and was less susceptible to photoinhibition. The importance of both strategies for plant primary production was analysed with a three-dimensional canopy photoinhibition model (CANO-PI). Simulations indicated that high variability in leaf angle orientation in Q. coccifera resulted in whole-plant carbon gain during the summer, which was 94 % of the maximum rate achieved by theoretical homogeneous leaf orientations. The high spatial variability in leaf angle orientation may be an effective compromise between efficient light harvesting and avoidance of excessive radiation in evergreen plants and may optimize annual primary production. Whole plant photosynthesis was strongly reduced by water stress and photoinhibition in C. monspeliensis; however, the simulations indicated that growth-related structural regulation of light interception served as an important protection against photoinhibitory reduction in whole-plant carbon gain.

Comments

Originally published by Elsevier. Publisher's PDF and HTML fulltext available through remote link.

Recommended Citation

Werner C, Ryel RJ, Correia O, Beyschlag W (2001) Structural and functional variability within the canopy and its relevance for carbon gain and stress avoidance. Acta Oecologica 22:129-138.