The Stomatal "Digital Twin": A Quantitative Systems Biology Platform for Unraveling Guard Cell Dynamics and Engineering Future Crops

Stomata are pivotal regulators of plant carbon-water balance, yet their complex, nonlinear dynamics—governed by intricate networks of ion transporters, signaling molecules, and metabolic reactions within guard cells—have long resisted intuitive understanding and rational manipulation. Here, we present a perspective on the development and application of a "digital twin" for stomatal guard cells, centered on the OnGuard family of quantitative systems models. This platform integrates decades of molecular, biophysical, and kinetic data into a rigorous computational framework, creating a "virtual proving ground" where environmental conditions can be simulated and genetic perturbations tested in silico . By encoding the fundamental constraints of mass and charge conservation alongside experimentally derived transporter kinetics, the model generates emergent behaviors that recapitulate complex physiological responses and, crucially, yields experimentally validated predictions that uncover previously hidden regulatory nodes. We discuss how this iterative cycle of prediction and validation has revealed unexpected homeostatic networks and context-dependent transporter functions. Finally, we argue that extending such modeling approaches to incorporate larger-scale physiological modules—including mesophyll photosynthesis, leaf hydraulics, and canopy-scale fluxes—will enable true multi-scale global simulation analysis, transforming our ability to predict and design crop performance under real-world conditions