Different types of root system
I. Tap root system:
The sample of sapling, which we have collected just now, has a complex tap root system. In this root system we can find a central axis. It is thicker at its base and gradually becomes thinner down towards the tip. This portion is called primary root or tap root. A set of lateral branch roots, comparatively thinner, emerge from the primary root. These are secondary roots. From a secondary root grow some very fine roots, which are called tertiary roots. The primary, secondary and tertiary roots form a detailed network within the soil. It is called tap root system.
Definition: The root system consisting of primary, secondary and tertiary roots is known as tap root system.
II. Fibrous root system:
Collect saplings of paddy, wheat or onion. If you observe it in the same process you
can find that these root systems do not have any primary root.
Numerous thread-like roots grow in a bunch from the base of the stem instead. These are called fibrous roots.
Definition: The root system, where primary, secondary and tertiary roots are replaced by large number of minute thread-like roots, is known as fibrous root system.