Category : 11th Class
The root is usually an underground part of the plant which helps in anchorage of plant in soil and absorption of water and minerals from the soil. The root with its branches is known as the root system.
Characteristics of the root
(1) The root is the descending portion of the plant axis and is positively geotropic and negatively phototropic.
(2) It is non-green or brown in colour.
(3) The root does not bear nodes, internodes, leaves and true buds.
(4) Usually the root tip is protected by a root cap.
(5) The root bears unicellular root hairs.
(6) Lateral roots arise from the root which are endogenous in origin (arise from pericycle).
Parts of the root
(1) Region of root cap : The tip of the root is called calyptra or root cap. It is for protection of root tip against any injury. It is formed from meristem called calyptrogen. Pandanus is the only plant with multiple root caps. In the aquatic plants like Pistia, Lemna and Eicchornia instead of root caps, they have root pockets for buoyancy. The root caps are absent in parasites and mycorrhizal roots.
(2) Region of cell formation or meristematic zone : This region of cell division lies protected below the root cap. It comprises of closely arranged, small, thin walled and isodiamatric cells which have dense protoplasm. Vacuoles of the cells are either reduced in size or absent.
(3) Region of cell elongation : It lies behind the growing point. Cells of this region lose power of division. The cells elongate due to vacuolation i.e., formation of vacuoles.
This region chiefly concerns with absorption of minerals along with some amount of water.
(4) Region of cell differentiation or maturation (Root hair zone) : In this region elongated cells are differentiated into permanent tissues depending upon the functions they have to performs. It lies adjacent to the meristematic region some cell of the outermost layer of cells in this region develop root hairs. Most of the water absorption occurs through this region.
Types of root
Tap root : The tap root system develops from radicle of the germinating seed. It is also called the normal root system. The tap root system is present in dicotyledonous plants.
Adventitious root : The root system that develops from any part of the plant body other than the radicle is called the adventitious root system. It is mostly seen in monocotyledonous plants. In grasses, fibrous root system is present.
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