The root is non-green, cylindrical descending axis of the plant that usually grows into the soil (positively geotropic). It develops from the radicle which is the first structure that comes out when a seed is placed in the soil. Root is responsible for absorption of water and nutrients and anchoring the plant. I.
Characteristic features • Root is the descending portion of the plant axis. • Generally non-green in colour as it lacks chlorophyll. • Does not possess nodes, internodes and buds (Exception in sweet potato and members of Rutaceae, roots bear buds which help in vegetative propagation) . .
Types of root system Tap root system Fibrous root system Figure . : Types of root system I. Tap root system Primary root is the direct prolongation of the radicle. When the primary root persists and continues to grow as in dicotyledons, it forms the main root of the plant and is called the Tap root.
Tap root produces lateral roots that further branches into finer roots. Lateral roots along with the branches together called as secondary roots . II. Adventitious root system Root developing from any part of the plant other than radicle is called adventitious root.
It may develop from the base of the stem or nodes or internodes. Example: Monstera deliciosa, Piper nigrum . In most of the monocots the primary root of the seedling is short lived and lateral • It bears root hairs (To absorb water and minerals from the soil) • It is positively geotropic and negatively phototropic in nature. II.
Regions of root Root tip is covered by a dome shaped structure made of parenchymatous cells called root cap. It protects the meristematic cells in the apex. In Pandanus multiple root cap is present. In Pistia instead of root cap, root pocket is present.
A few millimeters above the root cap the following three distinct zones have been classified based on their meristematic activity. . Meristematic Zone . Zone of Elongation .
Zone of Maturation Root hair Region of Cell maturation Region of cell elongation Region of cell division