The part of the sapling which comes out of the seed coat and moves towards the soil or earth is known as Radicle. This radicle further develops into the primary root in case of tap root system or may be replaced by a large number of roots in case of a fibrous root system. Other than these, roots do develop from different parts of plant which are known as Adventitious roots.
These roots undergo modifications to different forms for the purpose of performing special functions and these often become the point of gross identification of plants. Further the floral parts and the microscopical study will give a clear opinion regarding identification. This is due to the fact that the vegetative parts of the plant including the roots undergo drastic changes with respect to the characters like size, colour, thickness, etc according to the environmental conditions that exist. But floral parts being stable their characters are generally considered to be best tool to ascertain the identification including the species. Still, the knowledge about the character of roots are give a considerable input regarding identification of plants.
Generally the roots in a tap root system consist of a main root which has root cap at its tip or the growing end which may go deep into the soil to facilitate proper functioning like better anchorage and absorption of nutrients. The end near the surface of the earth will be more mature and contains many branches which are known as root hairs or rootlets. Other than this certain roots perform special functions like respiration, food storage, etc for which they undergo sufficient modification.
MODIFICATION OF ROOTS
The different modification of roots to serve different purposes under the category of Tap roots
- Fusiform Roots or Spindle Roots – They are modified to store food where they are thick in the middle and taper at the ends. For eg. Radish
- Conical Roots – They are the modified roots to store food where they are thick at the upper end and then taper towards the lower end like an inverted cone. For eg. Carrot
- Napiform Roots – They ar the modified roots to store food where the upper end are swollen and spherical while the lower ends taper into a thread like appearance. For eg. Turnip
- Tuberous Roots – This modification of roots are for the purpose of storage of foods where they don’t have any regular shape. It is due to the reason that the storage can result in any portion of the root making it swollen and fleshy at the region. For eg. Mirabilis
- Nodulated Roots – This variety of roots are resulted for the purpose of nitrogen fixation where the the bacteria form the nodules on the branches of roots. For eg. Black gram or other plants belonging to Fabaceae family.
- Respiratory root – These roots are the branches of main roots that arise from the soil by growing vertically upwards for the purpose of respiration. For eg. Rhizophora
The different modification of roots that come under the category of Adventitious roots are
- Tuberous adventitious root – They are similar to the category of Tuberous roots where they form the a bunch as they too get swollen but the difference here is the origin of these roots. For eg. Sweet potato
- Fasciculated root – This root modification too is for the purpose of storage of food where they appear in clusters and all are swollen with no definite shape. For eg. Dahlia
- Nodulose root – The modification where the root tips get swollen as nodules. Here too the basic function is to store food. For eg. Turmeric
- Moniliform root – The modification is for the purpose of storage of nutrition, this is characterised by multiple swellings like the beads at different places at regular intervals. For eg. Portulaca
- Stilt Root – The set of roots that arise from the lower nodes of the plant and enter the soil. The basic purpose is to provide additional support to the plant along with absorption of nutrition from soil. For eg. Sugarcane.
- Prop root – These roots arise from the branches of the plant usually large trees and grow downwards towards the soil with a basic purpose of providing support to the plant and its branches. For eg. Banyan
- Buttress root – The basic function of providing support and maintenance of the structural integrity, these roots arise at the base of the stem and spread in different directions on the soil. For eg. Arjuna
- Climbing roots – The roots that arise from nodes and help the plant to cling and attach itself with the support. For eg. Pepper
- Foliar root – These roots arise from the leaves and are basically for the purpose of propagation. For eg. Bryophyllum
- Sucking or Haustorial root – This is seen in the parasitic plants which has the basic function of obtaining nutrition from the body of host with which it is attached. For eg. Cuscuta
- Annulated root – This modification of roots are characterised by swelling with series of rings on them appearing like discs that are piled one above the other. For eg. Ipecac
The different modification of roots that come under the category of Fibrous roots are
- Tuberous roots – The roots are shapeless and appear singly giving a look as a tap root. These are different from the adventitious category on the basis of their origin. For eg. Sweet potato
- Fasciculated roots – The roots are tuberous and appear in clusters with a primary function of storing food. For eg. Asparagus
- Annulated roots – This modification of roots are characterised by swelling with series of rings on them appearing like discs that are piled one above the other. They are different from the category of adventitious roots based on the origin. For eg. Ipecac
- Reproductive roots – Here the roots form buds which grow into plants when they get the favourable conditions. The main function is to help multiplication of the plant. For eg. Sweet potato