Functions of roots:

They hold the plant firmly in the soil.

They absorb water with dissolved mineral salts from the soil using root hairs.

Some roots store food for example cassava.

Types of root systems:

There are two types of root systems:

Tap root system is where there is a main root with smaller branching lateral roots. Such a root system is characteristic of dicotyledonous plants for example beans, peas, hibiscus.

Fibrous root system is where there is no main root and all roots are of equal sizes. Such a root system is characteristic of monocotyledonous plants for example grass, maize, rice.

Modifications of roots:

Aerial roots: Some plants grow on branches of other plants and use them as a support.

Such plants are called epiphytes. Roots of such plants hang in the air and absorb water from the air. Such roots are called aerial roots for example in figs and orchids.

Clasping roots: Plants growing on branches of other plants also have roots for attachment. Such roots are called clasping roots for example in figs and orchids.

Breathing roots: Some plants grow in water or in mud where there may be no oxygen for the plant roots. So these plants send roots up out of the water to absorb oxygen from the air. Such roots are called breathing roots for example in mangrove.

Adventitious roots: These are roots that arise directly from the stem.

If these roots are large and thick, they are called buttress roots for example silk cotton tree.

If they are small and thin, then they are called prop roots for example in maize.

Internal structure of a dicotyledonous root:

Roots have no pith but have a star-shaped xylem in the centre and the phloem is between the arms of the xylem.

There is a cambium between the xylem and the phloem.

The cortex of the root is for storage of food.

The root hairs are for absorption of water and mineral salts.

Any lateral roots grow from the pericycle in the centre of the root.

An internal structure of a monocotyledonous root would look like this: