Regions of the roots:
The root exhibits four regions starting from the tip upwards.
They are:
1. Region of Cell division.
2. Region of Elongation.
3. Region of Root hairs.
4. Region of Maturation.
Region of Cell Division:
The root tip or the region of cell division consists of meristematic cells called the apical meristem. The meristematic cells divide repeatedly and produce new cells. The root tip is covered by the root cap. The outer cells of the root cap disintegrate to form mucilage, which acts as a lubricant and helps the root to easily penetrate into the soil.
Region of Elongation:
The region of elongation is present just behind the region of cell division. The cells in this region do not divide but elongate very rapidly, resulting in the elongation of the root.
Absorption of mineral salts mostly takes place in this region.
Region of Root Hair:
The region of root hair is present behind the region of elongation. The epidermal cells of this region produce unicellular, tubular outgrowths called root hairs.
Water is absorbed through this region. Root hairs increase the area of absorption of water.
Region of Maturation:
The region of maturation is the region behind the region of the root hair. It consists of permanent cells. Lateral roots are produced endogenously from this region.
One region of the root transforms into the other as the root grows.
Root cap:
Root cap or calyptra is a small protective structure present at the tip of the root. The root cap is produced from a special meristematic tissue called calyptrogen. A root tip usually has one root cap but persistent multiple root caps are seen in Screwpine (Pandanus).
Outer cells of the root cap disintegrate and form mucilage. This mucilage acts as a lubricant and helps in the easy penetration of root into the soil. Root cap is continuously produced. Root caps are absent in roots of parasites such as Cuscuta and Orobanche.
In free-floating plants like Pistia and Eichhornia, root pockets are present. Gases trapped in the root pockets help the plant to remain buoyant. If the root pocket is lost, it is not regenerated.
Types of root system:
There are two main types of root systems- the tap root system and the adventitious root system.
Tap Root System:
In taproot system, the primary root develops from the radicle of the embryo. It grows vertically into the soil and forms the taproot or the primary root. The primary root produces branches called the lateral roots or secondary roots.
Lateral roots arise in acropetal succession, that is, older and longer branches are away from the tip and younger and shorter branches are towards the tip.
The secondary root produces branches called tertiary roots. The taproot with its branches forms the tap root system.
Taproot system is seen in dicotyledonous plants.
Adventitious Root System:
When roots arise from any other part of the plant, other than the radicle, it is called adventitious roots.
Fibrous Root System:
Fibrous root system is a type of adventitious root system. In fibrous root system, the radicle initially develops into primary root, which perishes soon. Numerous, slender roots of more or less equal length develop from the base of the stem. As the root system appears like a tuft of fibres, it is called fibrous root system.
Fibrous root system is common in monocotyledonous plants.
General functions of the root:
The Root system has the following functions:
1. Fixation:
The root system fixes the plant firmly to the soil.
2. Absorption:
The root system absorbs water and mineral salts from the soil.
3. Conduction:
It helps in the conduction of water and mineral salts to the shoot system and food materials from the shoot system to other parts of the plant.