Hydraulic Redistribution - Causes

Causes

The movement of this water can be explained by the theory of water transport through a plant. This well established theory is called the cohesion-tension theory. In brief, it states that movement of water through the plant depends on having a continuous column of water, from the roots to the leaves. Water is then pulled from the roots to the leaves, through the plant system, by the difference in water potential between the boundary layers of the soil and the atmosphere. Therefore the driving force for moving water through a plant is the cohesive strength of water molecules and a pressure gradient from the roots to the leaves. This theory can still be applied when the boundary layer to the atmosphere is closed, e.g. when plant stomata are closed or in senesced plants. The pressure gradient is between soil layers with different water potentials; water moves through the roots from wetter to drier soil layers in the same manner as it does when the plant is transpiring.