Effects of Photoinhibition on Whole-Plant Carbon Gain Assessed with a Photosynthesis Model

Document Type

Article

Journal/Book Title/Conference

Plant, Cell and Environment

Volume

24

Issue

1

Publisher

Wiley-Blackwell

Publication Date

2001

First Page

27

Last Page

40

Abstract

A canopy photosynthesis model was modified to assess the effect of photoinhibition on whole-plant carbon gain. Photoinhibitory changes in maximum quantum yield of photosystem II (Fv/Fm) could be explained solely from a parameter (Lflux) calculated from the light micro-environment of the leaves. This relationship between Fv/Fm and the intercepted cumulative light dose, integrated and equally weighted over several hours was incorporated into the model. The effect of photoinhibition on net photosynthesis was described through relationships between photoinhibition and the shaping parameters of the photosynthetic light-response curve (quantum use efficiency, convexity, and maximum capacity). This new aspect of the model was then validated by comparing measured field data (diurnal courses of Fv/Fm) with simulation results. Sensitivity analyses revealed that the extent of photoinhibitory reduction of whole-plant photosynthesis was strongly dependent on the structural parameters (LAI and leaf angle). Simulations for a Mediterranean evergreen oak, Quercus coccifera, under climatic conditions which cause mild photoinhibition revealed a daily loss of 7·5–8·5% of potential carbon gain in the upper sunlit canopy layers, a 3% loss in the bottom canopy, and an overall loss of 6·1%. Thus, this canopy photoinhibition model (CANO-PI) allows the quantitative evaluation of photoinhibition effects on primary production.

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