Mathematical Simulation Of Stomatal Regulation Involving Root-Sourced Signaling ABA Under Soil Drought Condition

Plants developed a series of physiological mechanisms to avoid environmental stress, such as drought during long terms of evolution. Recently, lots of studies have supported the theory that the root sourced abscisic acid (ABA) played a central role in the root-to-shoot long distance signaling process and is an effective stomatal closing agent.The former stomatal regulation models involving root-sourced ABA have some problems, such as: the using of Penman-Monteith potential evapotranspiration equation to calculate plant transpiration is not precised enough, and the parameters are difficult to obtain. Meanwhile, the supposition that the soil water potential and root water potential in soil profile is invariability is not reasonable.In this paper, we replaced the Penman-Monteith equation by modified root water uptake model. The simulation results of the modified Feddes root water uptake model showed that, the model considered both soil water potential and root distribution in the soil profile, which could simulate the soil water change more correctly under different soil water conditions and root length dense distributions. Furthermore, the combination of the stomatal control model involving root-sourced signaling with the root water uptake model showed that, the simulation results were very closed to the actual daily stomatal changes under 2 different water treatments.In this paper we combined the stomatal control model involving the root-sourced signaling with the root water uptake model, which considered comprehensively the different soil water condition, root water potential and root length density distribution in soil profile, therefore depicted more accurately the ABA production processes in the root system, root ABA concentration in different soil layers, ABA concentration in xylem, and finally the controlling processes of the plant stomatal regulation by root-sourced ABA. The preliminary discussions of our model indicates that, the combination of stomatal control model involving the root-sourced signaling with the root water uptake model improves the simulation effect of the former model and optimizes the root-shoot communication theory, and make it possible to integrate the plant response mechanism to soil water stress and atmospheric water deficit. The model contributs to considerate comprehensively the plant water use processes and the stress responsible processes, which makes a further step in plant water relationship theory.