The rise of sap

Like blood in our body, sap circulates in plants through special vessels. Unlike us, there is no pump (heart) to move aroud the sap that contains food, especially to the leaves.

3 phenomena can explain why, without the help of a pump, the sap can rise to the leaves:

• Root growth : the roots absorb water which gives a 'bottom to up' direction to the sap.
• Capility : this phenomenon allows a liquid to rise by attraction (as in a blotter for example)
• The evapo-transmission of the leaves. Heated by the sun, leaves lose water which creates a depression in the upper parts of the plants and sucks the sap from the bottom to the top.

The principle of sap circulation in a plant can be visualized by a simple experiment.

By irrigating a plant with tinted water which makes it possible to follow the progress of the water in the plant.

This DIY was carried out as part of the newspaper 'Campus Junior' of the University of Geneva.