Abstract: Under soil drought condition,root sourced signal abscisic acid (ABA) plays an important role in the long distance signaling process,and can be a measurement of soil water availability.ABA is also an effective stomatal closing agent,and acts to reduce transpiration and canopy water loss.This paper briefly introduced the physiological mechanism and theoretical model about the stomatal regulation by root sourced signaling,and indicated that the combination of this model with root water absorption model and stomatal conductance model could be more effective in depicting the response of plant to soil drying and atmospheric drought.In addition,some effective irrigation approaches,such as regulated deficit irrigation (RDI),partial root-zone drying (PRD) and controlled alternative irrigation (CAI) were profited from the mechanism of plant water use regulation by the root sourced signaling.These irrigation measures favored to reasonably distribute available soil water in root zone.Root signaling system also played important role in regulating root growth and its development,retarding shoot growth to adjusting root shoot ratio,and optimizing assimilation allocation to favor to improve reproductive development.These processes hold substantial promise for enhancing crop water use efficiency.

Key words: Root sourced signaling, Stomata, Model, Water use efficiency, Water saving