Towards a quantitative description of the impact of local light environment on morphological plasticity in cereal crops using functional structural plant models

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The morphological plasticity of plants in general, and of assimilating leaves in particular, is strongly influenced by the amount and quality of available light. Plant ecologists call this behavior sun vs. shade leaf dichotomy. The aim of my post-doctoral work is to investigate to which extent cereal leaves, as most important assimilating organs, adapt to the light environment, and whether quantitative relationships between the amount of absorbed light and morphological and physiological leaf traits can be discovered. To do this, the application of a Functional-Structural Plant Model (FSPM) is proposed. The modeling approach suggested here combines the computer-based reconstruction of a cereal canopy and the computation of light absorption by individual leaves with a radiation transfer model. Morphological data is obtained from a two-season field trial (2007-2009) on winter wheat (Triticum aestivum L. cv. Soisson), where effects of sowing date and density on plant morphology are investigated. Using this data the 3D architecture of wheat is reconstructed using the model ADEL wheat. Model validation is performed by comparing modeled and measured data of ground cover and leaf area index. Using the ‘virtual wheat canopies’ calculated this way amount of absorbed light by leaves will be calculated and related to orientation, width and specific mass measured on the respective leaf. Potential relationships for the investigated genotype - environment combinations will be described with mathematical functions. These quantitative relationships are applicable in FSPMs towards a simulation of plants light foraging behavior and its consequences for the 3D morphology, which lastly contributes to an improved comprehension of the morphological adaptation of plants (leaves) to their light environment in particular and to mechanisms of cereal plasticity in general. This will finally lead to a better understanding of how technical choices in cereal production, here sowing density or date, affect crop morphology and harvestable yield under particular environmental conditions.