5.1 THE ROOT

5.1 THE ROOT 

In majority of the dicotyledonous plants (Di-Two and Cotyledons- Embryonic Leaves in a Seed. Dicotyledons/ dicots are one of the two groups into which all the flowering plants were formerly divided), the direct elongation of the radicle leads to the formation of primary root which grows inside the soil. It bears lateral roots of several orders that are referred to as secondary, tertiary, etc. roots. The primary roots and its branches constitute the tap root system, as seen in the mustard plant (Figure 5.2a). 

In monocotyledonous plants, the primary root is short lived and is replaced by a large number of roots originating from the base of the stem and constitute the fibrous root system, as seen in the wheat plant (Figure 5.2b). 

In some plants, like grass, Monstera and the banyan tree, roots arise from parts of the plant other than the radicle and are called adventitious (not expected or planned) roots (Figure 5.2c). 

The main functions of the root system are absorption of water and minerals from the soil, providing a proper anchorage to the plant parts, storing reserve food material and synthesis of plant growth regulators.

5.1.1 Regions of the Root 

The root is covered at the apex by a thimble-like (a small metal object worn on the end of finger to protect it while sewing) structure called the root cap (Figure 5.3). It protects the tender apex of the root as it makes its way through the soil. 

A few millimetres above the root cap is the region of meristoóematic activity (Greek word merizein means to divide. The meristemtic cells, found in plants are the undifferentiated or incompletely differentiated cells which are totipotent i.e. capable to develop into all the other tissues and organs that occur in the plant).  The cells of this region are very small, thin-walled and with dense protoplasm (living part of a cell that is surrounded by a plasma membrane). They divide repeatedly. The cells proximal to this region undergo rapid elongation and enlargement and are responsible for the growth of the root in length. This region is called the region of elongation. The cells of the elongation zone gradually differentiate and mature. Hence, this zone, proximal to region of elongation, is called the region of maturation.  From this region some of the epidermal cells form very fine and delicate, thread-like structures called root hairs. These root hairs absorb water and minerals from the soil.