Root Pressure Theory - Practice Questions & MCQ

• It was proposed by Joseph Priestley.
• The term ‘root pressure’ was given by Stephan Hales.
• The definition of root pressure was given by Stocking.
• Root pressure can be defined as the hydrostatic pressure that develops in the tracheary elements of the xylem. 
• It develops due to an active process. The metabolic energy is spent in the generation of root pressure.
• This theory is supported by Guttation.
• Guttation occurs during the nights and early mornings when evaporation is low and the excess water absorbed by the roots collects in the form of droplets around the special openings veins called hydathodes.
• Hydathodes are present at the tips and margins of the leaves.
• Guttation is the loss of water in the form of liquid.
• Root pressure is measured by manometer.
• It is maximum when the rate of transpiration is very low and water absorption is very high.

Mechanism of Root Pressure Development:

• The non-osmotic active absorption of water from the soil by the root hair cells and then the movement of water to the xylem elements generate a hydrostatic pressure.
• This pressure is called the root pressure.
• It is the result of the expenditure of energy to create high osmotic pressure in the root hair cells as well as in the xylem elements so that water can follow the concentration gradient.
• Root pressure is sufficient to raise the water column up to 60-70 ft height.
• But it cannot cause ascent of sap in tall trees that are more than 100 ft tall.
• Root pressure is not seen in gymnosperms.
• It is also absent from the actively transpiring leaves.

                             Guttation on the Margins of the Leaves