Types of Roots: On the basis of their origin, roots are of two types – tap root and adventitious root.
(a) Tap root:
On germination of a seed, the radicle elongates into primary root or true root or tap root. In dicot plants, the tap root is persistent and produces lateral roots such as secondary roots, tertiary roots etc. All lateral roots arise in acropetal succession i.e. younger roots towards apex and older roots towards base. The tap root and its branches constitute the tap root system.
(b) Adventitious root:
These are the roots that grow from any part of the plant other than radicle. In monocot plants, the tap root is short lived and soon replaced by adventitious roots. A group of adventitious roots and their branches constitute adventitious root system. On the basis of their origin, the adventitious roots are of following three types –
- Fibrous roots:
These are a cluster of equally prominent thread-like roots that develop either from the base of stem (e.g., rice, wheat, maize, onion etc.) or from the nodes of horizontal stem (e.g., grass, wood sorrel etc.)
- Foliar roots:
They arise from petiole (e.g., Pogostemon, rubber plant etc.) or veins of leaf due to some injury. These can also be induced by application of hormones. Some foliar buds can produce foliar roots, e.g.,Bryophyllum, Begonia etc.
- True adventitious roots:
They arise from the nodes and intemodes of the stem, e.g.,Prop roots of banyan, stilt roots of sugarcane, clasping roots of money plant and roots from the stem cuttings
