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

一般来说，植物的形态可塑性，特别是同化叶片的可塑性，受到可用光的数量和质量的强烈影响。植物生态学家将这种行为称为阳光与阴影叶片二分法。我博士后工作的目的是研究谷物叶片作为最重要的同化器官，在多大程度上适应光环境，能否发现吸收光量与叶片形态生理性状之间的定量关系。为此，提出了功能-结构植物模型（FSPM）的应用。本文提出的建模方法将基于计算机的谷物冠层重建和单个叶片光吸收计算与辐射传输模型相结合。形态学数据来自于对冬小麦（Triticum aestivum L. cv.）进行的两季田间试验（2007-2009）。Soisson)，在那里研究了播种日期和密度对植物形态的影响。利用这些数据，利用ADEL小麦模型重构小麦的三维结构。通过比较地表覆盖和叶面积指数的模型数据和实测数据，对模型进行了验证。使用“虚拟小麦冠层”，通过这种方式计算叶片吸收的光量，并将其与各自叶片上测量的方向、宽度和比质量相关联。所研究的基因型-环境组合的潜在关系将用数学函数来描述。这些定量关系适用于FSPMs，用于模拟植物光觅食行为及其对3D形态的影响，最后有助于更好地理解植物（叶片）对光环境的形态适应，以及谷物可塑性的一般机制。这将最终使人们更好地了解谷物生产中的技术选择，如播种密度或日期，在特定环境条件下如何影响作物形态和可收获产量。

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.