Roots are an integral part of the plant system. Do you know why? Roots help the plants in absorbing water and essential nutrients from within the soil and help to anchor the plant as well its parts firmly into the ground. In this article, we will discuss about the Taproot System. The root system consists of other two main roots: fibrous roots and adventitious roots. So what is taproot? Let’s get into the details of the taproot system with its types, modifications, and examples.
What is a Taproot System?
Taproot consists of several roots that protrude from the radicle of a mature embryo. When the plant matures, this embryo tends to fall off. During this period, the taproot gets matured into fibrous root with many branches spread all over. The taproot system is considered the strongest as it is the largest and the thickest of all the different types of roots. A Taproot has three main parts: primary roots secondary roots, and tertiary roots.
The primary root is also known as the taproot. Arising from the taproot are tiny lateral roots, which are also regarded as secondary roots. This secondary root further produces even smaller roots called tertiary roots. These secondary and tertiary roots help in increasing the surface area for the absorption of water and vital minerals from within the soil. All the secondary and tertiary roots are found in the acropetal patterns.
The Direction of the Roots
Well, if we talk about the direction of these roots, the primary root is in a vertical manner, secondary roots are arranged in an oblique or horizontal way, while the tertiary roots run in various directions. Now, let’s get into what are the types of tap root system in detail!
Types of Taproot System
A taproot has two different types, deep and surface feeder. Deep feeder roots are generally found in big trees. They tend to penetrate the deepest layers of the soil.
The taproot of surface feeders may not extend much. The secondary roots extend further, generally horizontally towards the soil surface. The cymose taproot system is another term for this type of system. Thin fibrous roots make up the surface feeder or cymose taproot system of several perennial crops. These thinner perennial plants can also be known to possess a fibrous taproot system. Roots have to perform a lot of biological functions in order to support the plant. For that reason, the roots have to undergo certain changes in their structure and morphology. Now, let us look at what are the modifications of the taproot system:
Roots For Food Storage
Storage roots’ are roots that have the ability to preserve food. These roots have been engineered to allow them to retain food provided by the plants within them. This food is later used by the plant as a source of nutrients. The storage roots are generally beneficial to humans. Carrot, radish, sweet potato, and other root vegetables are common in our daily diet, which are great examples of food storage taproot system.
The layers of the principal taproot or main root enlarge in storage roots and begin to accumulate particles of food. Such roots appear thick or inflated as a result of the buildup of food. The secondary or tertiary roots, on the other hand, continue to stay thin. Storage roots can be differentiated into four main categories depending on their structure:
Let us look into each type to know the changes occurring in the taproot system.
This type of root system has a primary root that initiates from the stem base, and it keeps on decreasing when it comes to the root apex. It has two ends: one is tapered and the other is swollen. It has a fleshy cone-like structure, and a number of thread-like secondary and tertiary roots that emerge from the length of the conical taproot.
Example of Conical Taproot: Daucus Carota
The main difference between fusiform and conical taproot is tapering occurrence. In a conical root system, the tapering happens only at one end. While in the fusiform taproot system, tapering occurs at both ends. This kind of storage taproot constitutes a primary root that is tapered from both ends. These ends are the apex of the root and the base of the stem. It looks like a spindle that is thickest at the center and keeps on narrowing as it reaches the end of the root.
Example of Fusiform Taproot: Indian Radish and European Radish
Having an appearance of like a sphere, this root is very thick at the stem base. In this taproot, the swelling occurs at the base, which does not get narrower towards the end. Tapering happens at the root base in napiform roots.
Example of Napiform Taproot: Turnip and Beetroot.
There are certain roots that do not possess any particular appearance or shape. These roots are known as tuberous roots. It is an enlarged root that turns fleshy to store food.
Example of Tuberous Taproot: Mirabilis Jalapa and Cassava
Roots For Respiration
There are certain kinds of roots that are responsible for the aeration of the plant. Such kinds of roots can help the plant in fixing certain gases and thus help in the breathing of the plants. The respiratory roots are of two basic types:
Taproots that are unevenly swelled are known as nodulated roots. The main, secondary, and tertiary roots swell, and these are referred to as ‘root nodules’ or ‘tubercles.’ Tons of nitrogen-fixing microorganisms from the species Rhizobium populate these root nodules. Because the nitrogen in the air cannot be physically consumed by plants, the Rhizobium found in the nodules assists in the conversion of this nitrogen into something like a form which can be readily utilized. Nitrogen fixation is the mechanism of taking atmospheric nitrogen from the environment and converting it into biological nitrogen molecules. Leguminous plants absorb nitrogen from the soil through their roots. The bacteria absorb the nitrogen in return for basic necessities. Such a type of interconnection is referred to as mutualism. Mutualism is a sort of connection in which both species benefit each other.
Examples of Leguminous Plants: Pea, Groundnut, Gram, Soyabean, Fenugreek
Pneumatophores are aerial roots that emerge from the ground to assist the host in breathing. As a result, they’re called respiratory roots. These are found in plants that grow in mangroves and marshes. The sediment of the mangrove is dense and slippery, preventing the air from passing through. As a result, the roots of these kinds of plants emerge from the ground to breathe. Pneumatophores are a kind of fungus that grows directly upwards. Pneumatophores possess a negative geotropism. The lenticels which are microscopic pore-like openings on the surface of the root, aid in the gaseous exchange.
Examples of Pneumatophores: Sonneratia, The black mangrove, and the Bald cypresses