The root is the descending part of the plant axis, which lies inside the soil. It contains the following parts like
- Root cap
- Root Hair
- Zone of elongation (region of elongation)
- Zone of maturation (region of maturation)
The root typically does not contain chlorophyll, and therefore, it is nongreen. It bears lateral branches and a protective cap at the apex.
Root doesn’t have nodal divisions; however, it is divided into five main areas on the basis of the growing stage of cells present in that area. The five areas are.
Root doesn’t have nodal divisions; however, it is divided into five main areas on the basis of the growing stage of cells present in that area.
The Five Parts of Plant Roots are
A root cap
- It is also called calyptra and is a cap-like protective covering over the tip of the root.
- The root cap is the region of graviperception that helps plants to perceive the direction of gravity by the plant and maintain geotropism.
- The cap is multicellular and made of parenchymatous tissue.
- These cells secrete mucilage, which acts as a lubricant, thus allowing the root to pierce the soil and descend downwards with greater ease.
- The outer cells of the cap get sloughed off due to friction, and these cells are replaced by new cells from a growing part.
- A broken or injured root cap is replaced.
- In many aquatic plants, the tip of the root is covered by a loose elongated sheath called a root pocket.
- This root pocket functions as a balancer. An injured root pocket is not replaced.
Growing point
- It is also called the meristematic region, a small area in the subapical region.
- The cells present here are meristematic in nature and are thus small, thin-walled with dense protoplasm.
- It occupies a small fraction of the root length, and the cells here divide continuously to add new cells to the root cap and the zone of elongation.
- Thus it is responsible for the increase in the length of the root.
Zone of elongation
- This region is situated just behind the meristematic region and is about 4 to 8 mm in length.
- This area continuously receives new cells from the meristematic part.
- The cells of this region have large central vacuoles and peripheral cytoplasm and can thus absorb water and minerals from the soil.
- The cells of this region also elongate and bring about growth in the length of the root.
Zone of root hairs
- This region is also called the zone of differentiation or zone of maturation, or region of maturation.
- In this area, the primary cells differentiate to form various cells with specific functions.
- Xylem and phloem are formed to help in the conduction of food, water, minerals, hormones, etc in vascular plants.
- The cells on the surface differentiate and develop into epiblema.
- Epiblema cells differentiate and develop into the tubular outgrowth of root hairs, which help in the absorption of water from the soil.
- This region is 1 to 6 cm in length. Root hairs are not permanent, and they shrivel up after some time.
- However, the growth of the root keeps the size of the root hair zone nearly constant.
- The new cells pass into the zone of elongation, and the oldest cells pass into the zone of mature cells.
Zone of mature cells
- This zone contains mature cells. The surface in this zone has thick-walled, impermeable cells through which there is no absorption of water or minerals.
- At places, endogenous growth produces lateral roots.
- Secondary growth may occur in this zone in dicots and gymnosperms.
Also, see storage roots.