Transpiration pull
Stomata are found on the leaf surface.
The suction force of transpiration is caused by the loss of water vapour through the stomata.
Transpiration pull is the force responsible for moving water all the way up the stem, to the leaves and is the most powerful of the three forces.
Water moves from the xylem in the main vein of the leaf, through the spongy parenchyma, into the intercellular air spaces and out through the stoma as water vapour.
The water moves from the leaf surface by evaporation.
This creates a water potential around the leaf, resulting in a negative pressure developing in the xylem.
This suction force is transferred along the leaves and stem, resulting in a decrease in the water potential of the roots.
Transpiration may cause excess water loss resulting in the plant wilting.
Excess wilting will cause death.
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