Hello Biology Lovers, the title of our today’s blog is Root – External Morphology, Modifications, Work and Root system (Root Morphology, Modification of root, Root system and Work of Root)


Root


Underground part of the plant that develops from the embryo’s radicle during the seed germination, is called root. The first generated root is called Primary Root. The lateral root derived from these primary roots are called secondary Root and Tertiary Root.


 Root System


There are three types of root system found in plants –


The Taproot System


Primary root and their branches form the taproot system. It is found in Dicot plants.

Root Morphology, Modification of root, Root system and Work of Root


The Fibrous Root system


Primary root has short life in Monocots plants. Due to which roots of many equal lengths are formed in places of the primary root. Such roots are called fibrous root system.

Root Morphology, Modification of root, Root system and Work of Root


The Adventitious Root System


In some plants, roots develop from the pneumatic parts of the plant. Such roots are called adventitious root system. Example Grass and Banyan.

Root Morphology, Modification of root, Root system and Work of Root


Root – External morphology, conversion and Root system (Root Morphology, Modification of root, Root system and Work of Root)


Characteristics of Root


  • Chlorophyll is absent in roots.
  • Positive Geotropic, Positive Hydrotropic, and Negative Phototropic are found in the root.
  • There is a lack of nodes, internodes, bunds, and leaves in the root.
  • Radial vascular bundles are found in the roots.
  • The unicellular root hair is found in the epiblema of maturation area of the root which absorbs the water.
  • Lateral roots are derived by the Pericycle which is the endogenous type.

Zone of Root


The root has been divided into four areas-


Root Cap


It is the cap (top) of the root. Which protects the meristematic tissue from friction. In the aquatic plant-like Lemna and Pistia, the root pockets are found in the place of root cap.


Meristematic Region


This is the area of divisive cells. Which divides continuously and increase the length of the roots.


Elongation Region


The length of the root increases by increasing cells size made of meristem in this region.


Mature region


There are mature and differentiated cells in this area. Which differentiates into the epidermis, cortex, Pericycle, pith, xylem, phloem etc. The root hairs are found on their epidermis.


Modifications of Roots


Some roots are converted into different shapes and structures for doing specific work. They are called modified root.
The modified roots are the following types –


Storage Root


Some roots store the reserve food material and build the storage root. Storage root are the following types-


Modification of Taproot



Fusiform


In the radish, the taproot store foods and swells. It is swollen in the middle and thin on the edges.


Conical


In carrot, the taproot stores food and swells to look like a conical structure. It is thick upward and thin towards the bottom.


Napiform


In turnip (Brassica napus) and Beet (Beta vulgaris), the taproot store foods and became spherical like a pot i.e it is swollen in the middle.


Tuberous


In Gul Abbas or Mirabilis jalapa (4’ O clock plant) and Trichosanthes dioica (Pointed ground or parwal), the storage root does not have a definite shape and is called tuberous root.


Modifications of Adventitious Root



Tuberous root


Sweet potato (adventitious root) stores food materials and swells with no definite structure. Adventitious roots emerge from the nodes of the stem.


Fasciculate Root


Adventitious roots in Asparagus and Dahlia form more than one lantern structure of roots after storing foods. This is called fasciculate root.


Nodulose root


In Mango ginger (Curcuma amada) and Arrowroot (Cosuts speciosus) adventitious root swell only near their apices and form beads like structure. These are called nodulose roots.


Moniliform or Beaded root


In bitter gourd (Momordica charantia) and yam, adventitious roots are alternately swollen and form a beaded structure.


Annulated Roots


In Ipecac (Cephalis ipecacuanha), the roots form the ring structure in which roots looks like a number of discs placed one above another.

External Morphology, Modifications, Work and Root system External Morphology, Modifications, Work and Root system


Modification for Mechanical Support 



Prop Roots


In some plants, branches give rise to the aerial roots. These roots grow and enter the land. It provides support to the plant like a pillar. Example Banyan (Ficus benghalensis)


Stilt Roots


In the sugarcane, maize, and pandanus, the roots emerge from the nodes of the stem. They grow and enter into the soil to provide support to the stem.


Climbing Roots


Adventitious roots help the plant to climb on another plant. These types of the root are found in betel vine and Scindapsus officinalis


Buttresses Root


In some big trees, the root from the lower part of the trunk becomes thick and spread like a plank. Example Terminalia catapaa, Bombax ceiba.


Clinging Root


Epiphytes plants like orchids cling to their support. They have the special clinging root which enters cracks of their support and fix the plant.


Floating root


The adventitious roots of the aquatic plants grow and form nodes that contain air sacs. The buoyancy of these roots helps in plants floating. Example Onagraceae (Fussiaea repens)


Contractile Root


Onion contains special roots. The roots contract or swell so that the aerial shoot or underground part of the plant are kept at a proper level in the soil.


Root Thorns


The Adventitious roots turn out from the base of the stem and become hard pointed, sharp and thorn like which helps the plant in climbing up. Example Pothos armatus


Leaf Root


It develops from the core of the leaflet which develops a new offspring. Example Bryophyllum


Modifications of Roots for Physiological Reasons



Respiratory Roots


In the plants found in marshy areas, the roots grow vertically up into the air. These roots are called pneumatophores. It helps in respiration. They contain lenticels that are known as pneumathodes. Examples Rhizophora, Avicennia


Hygroscopic or Epiphytic Roots


These aerial roots are greenish and covered with a spongy velamen tissue. With the help of velamen, these roots absorb water. It is also called aerial absorbing roots.


Assimilatory Roots


Due to the presence of chlorophyll, these roots produce food through photosynthesis. Example – Tinospora, Trapa.


Reproductive Roots


In the sugarcane and dahlia, adventitious roots produce offspring by vegetative propagation.


Sucking root


In the parasitic plants, adventitious roots enter the plant and receive food from them. It is also called Haustoria. Example – Dodder


Mycorrhizal Roots


Symbiosis is found between the fungus and root of pinus that is called mycorrhizal root.


Roots Nodules


Root Nodules are found in roots of Fabaceae plants, in which roots associate with symbiotic nitrogen-fixing bacteria like rhizobium.


Function of Roots


  1. Absorption and conduction of water and salts from the soil.
  2. Keep the plant stable in the land.
  3. Synthesis of plant growth regulators.
  4. Food storage
  5. Providing mechanical support

External Morphology, Modifications, Work and Root system External Morphology, Modifications, Work and Root system

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Root Morphology, Modification of root, Root system and Work of Root Root Morphology, Modification of root, Root system and Work of Root Root Morphology, Modification of root, Root system and Work of Root Root Morphology, Modification of root, Root system and Work of Root


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