A model for the analysis of stomatal dynamics - applied to critical simulations of experiments on oscillatory transpiration in oat plants

To explain transpiration results from experiments on stomatal oscillations in oat plants, it is shown by simulations on a model including both hydro-passive and hydro-active feedback that the model must include hydro-active control of the osmotic pressure of the subsidiary cells. Hydro-active feedback was used between the turgor pressure of the mesophyll cells, acting as sensor cells, and the osmotic contents of the subsidiary- and guard cells. In the model, a reduction of the turgor of the sensor cells results in an increase of the osmotic content of the subsidiary cells and a reduction of the osmotic content of the guard cells. Simulations showed that the hydro-active feedback to the subsidiary cells was always needed. However, it was also shown that it is an advantage to combine the hydro-active feedback to the subsidiary cells with hydro-active feedback to the guard cells. The added hydro-active feedback to the guard cells will prevent too high turgor levels in the guard cells when the stomata have closed at water stress with high light levels. The model consists of established evaporation- and plant waterflow models from literature, experimentally verified models on stomatal mechanics and new models of hydro-active feedback. The model explained results reported in experiments where the water potential of the root medium was lowered and in experiments where the potential rate of evaporation was increased.