Guard Cell Modelling Software



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The OnGuard software package was constructed for quantitative systems dynamic modelling of the stomatal guard cell. It incorporates explicitly all of the fundamental properties for transporters at the plasma membrane and tonoplast, the salient features of osmolite metabolism, and the major controls of cytosolic-free Ca2+ concentration and pH. OnGuard takes a structured approach to tier and interrelate elements, and gives ready access to parameters and equations ‘on the fly’ while enabling the network of components within each model to interact computationally.

The latest release (Version, Autumn 2012) includes a new feature, the “Cartoon Display” (available via the View menu); this displays a schematic representation of the guard cell pair, showing changes in stomatal aperture, along with selectable trans-membrane transporter and solute fluxes.


On-Guard is freely available, but is an expert system. Effective use requires a good working knowledge of guard cells, transport physiology, and an interpretive understanding of current-voltage curves. When publishing simulations and analysis using the software, please cite the following two articles:

Adrian Hills, Zhonghua Chen, Anna Amtmann, Michael R. Blatt and Virgilio L. Lew: “On-Guard: A Computational Platform for Quantitative Kinetic Modeling of Guard Cell Physiology.” Plant Physiology, 2012, 159:1026–1042.

Zhonghua Chen, Adrian Hills, Ulrike Bӓtz, Anna Amtmann, Virgilio L. Lew and Michael R. Blatt: “Systems Dynamic Modeling of the Stomatal Guard Cell Predicts Emergent Behaviors in Transport, Signaling and Volume Control.” Plant Physiology, 2012, 159:1235–1251.



* Direct and easy access to all model parameters, and facility to define solute compositions, transporter populations, biophyical and kinetic parameters.

* Automatic ‘smart’ time base that accelerates computational speed with minimum and maximum limits.

* A Reference State Wizard that aids establishing stable models.

* Simulation-time graphical display of current-voltage relations for transporters at both membranes.

* Simulation-time tabular display of all ionic and other solute contents for each compartment and fluxes between compartments, tabular display of related variables.

* Simulation-time graphical chart recorder of key variable outputs.

* Logging of all variables in spreadsheet-readable (*.csv) format.

*OnGuard is supplied with model parameter (*.obg) files for Vicia and Arabidopsis guard cells.

Pentium V or better CPU, running Microsoft Windows Vista or Windows 7; Administrator rights to install the package. We recommend a quad processor system for best results.