Types of Root

Depending upon their origin, roots are classified into two main types.

1. Tap roots or True roots.

2. Adventitious roots.

1. Tap Roots or True Roots:

A root that develops from the radicle of an embryo during seed germination is called a true root or tap root.

The tap root continues to grow and bears branches on it.

The main root is called primary root.

Its branches of first order are called secondary roots, and branches of second order are tertiary roots and so on.

The main root along with its branches form a tap root system e.g. Mustard (Brassica), Sunflower (Helianthus) , etc.

Presence of tap root system is a characteristic feature of dicotyledonous plants.

The tap root normally grows vertically downwards to a lesser or greater depth, while secondary and tertiary roots grow obliquely downwards or some grow horizontally outwards.

All lateral branches are produced in acropetal succession, i.e., the older and longer branches are near the base and younger and shorter ones are near the apex of main root.

2. Adventitious Root System:

A root that develops from any part other than radicle is known as an adventitious root.

Such roots may develop from the base of stem, nodes or from leaves.

In monocots, radicle is short-lived and from the base of stem a thick cluster of all equal-sized roots arises.

This is known as adventitious root system. e.g. Maize, wheat, sugarcane, etc.

It is also known as fibrous root system as the adventitious roots of grasses (monocots) look like fibres. Fibrous roots do not grow very deep into the soil.