CNW-Wheat: A Functional-Structural Plant Model Integrating Metabolic and Hydraulic Interactions in Grass Leaf Growth

Leaf growth is a critical process for plants exhibiting significant plasticity across environments and which largely determines their energy balance, carbon and nitrogen content and water status. It is essential to understand how metabolic and hydraulic constraints coordinate to determine leaf growth plasticity. However, whether this plasticity can emerge from organ-level resource availability and water status remains to be demonstrated. To address this complexity, we developed a novel model of grass that fully integrates leaf morphogenesis, carbon and nitrogen metabolism and water flows at the organ level within a 3D representation of the whole plant architecture. The deposition of water, carbon, and nitrogen in the growing leaf depends on the activity of the shoot organs and roots. Metabolic and water flows occur through single pools mimicking the phloem and xylem, respectively. Leaf elongation follows two distinct phases separated by the emergence of the previous leaf. During the initial exponential-like phase, leaf elongation is co-regulated by metabolite concentrations and xylem water potential. In the second phase, 3D leaf elongation is simulated using a turgor-driven growth approach, whereby metabolic concentrations affect osmotic potential. The model was evaluated against experimental data on winter wheat (Triticum aestivum), demonstrating that complex patterns of leaf elongation, diurnal variations and resource allocation gradients can emerge from the dynamic coupling of turgor-driven expansion and C-N substrate deposition. Furthermore, our simulations confirm that the hypotheses implemented in the model can also account for the response of plant physiology and leaf growth under drought conditions. This study demonstrated that CNW-Wheat is a functional framework to explore G×E.