The Root system is an essential part of the plant. It serves many purposes like anchoring the plant in the soil, helps in getting it the water and nutrients it needs and sometimes, storing the excess of food that the leaves produce which would be used in times of scarcity. Apart from that, the hidden system does a lot more work by modifying itself in various specialized forms in different plants according to their needs! Roots have evolved differently in different plants based on the place they grow and based on the needs of the plants. I’m narrating some of the modifications of roots known to science so far… There may be additions to this list in the future as new discoveries are made! This is just the basics to understand how roots get modified in various plants to serve their purposes… Let’s jump in!

Modifications of tap roots

Conical

Conical roots are modified into roughly cone-shaped structures. They are broad at the top and go on tapering at the other end. The broad end is attached to the plant and the free end is tapering to end in a sharp point. This type of root is a modification for food storage. A Carrot is a great example of a conical root.

Fusiform

Fusiform roots are a bit swollen in the middle when compared to both the ends. Imagine a Radish for this type of root. This root is also a modification to store reserve food.

Napiform

Napiform roots are extremely swollen at the anterior end and suddenly tapering to a pointy end at the posterior end. Beetroots and Turnips are a great example of a napiform root. This is also a modification for reserve food storage in the form of sugars and starch.

Modifications of adventitious roots

For storage

Tuberous

Tuberous roots look like tubers in appearance. They are found underground but the tubers are a modification of stem and have buds while tuberous roots don’t have buds on them. However, both primarily act as storage organs in plants. For example, sweet potato is a tuberous root while the potato is a tuber.

Fasciculated tuberous roots

Fasciculated roots are similar to tuberous roots but they occur in tufts immediately underneath the stem. They look similar to tuberous roots but occur as a tuft of roots. Dahlia is a good example of fasciculated roots.

Nodulose roots

In some plants like Turmeric, Mango ginger, and Arrowroot, some roots get swollen to store extra energy although they have rhizomes which store reserve food. There are two types of underground parts in turmeric, for example. It has underground rhizomes which are flat and finger-like. The ones that are swollen and spherical are the tubers. They occur at the tips of the adventitious roots.

Moniliform roots

Moniliform roots are the ones that look as if beads on a string. They have nodules like thickening at regular intervals. Grasses, Momordica have moniliform roots.

Annulated roots

In Ipecac, the roots look like they are made up of concentric rings. It appears as if the rings were placed one on another consequently which gives it a strange appearance.

Tubers of Orchids

In some orchids like Habenaria and Orchis, being terrestrial orchids, the fibrous roots are modified into tubers.

For support

Prop roots

Ficus benghalensis (Banyan tree) is the best example of prop roots. Being a huge tree, Banyan has evolved a great way to support its weight. It has developed strong roots that emerge from under its branches, grow downwards into the soil and strengthen its enormous branches. In this way, the tree is able to grow into one of the massive ones in the World. The World’s largest Banyan tree is in Acharya Jagadish Chandra Bose Botanical Garden in Howrah, West Bengal, India. It has spread to an area of a whopping 3.5 acres!

Stilt roots

Some plants have also developed some roots from the base, just above the soil and anchor the plant or tree to the soil. This is seen in some Monocots like Maize, Sugarcane and Myrisistica swamps (a very fragile forest type in the Western Ghats, India) which are dominated by the trees of the Myristicaceae family.

Climbing roots

Some climbers do not use tendrils or twine around their support as normally climbers do. This peculiar behavior is observed in the climbers of the families Araceae and Piperaceae. Pothos and Piper climbers have climbing roots at nodes that hold to the surface firmly helping the climbers to climb up huge trees in the rainforests.

Haptera or holdfasts

Some climbers like Ficus pumila (wall creeper) and Hedera helix (English Ivy) have special types of roots developing from their nodes which hold tightly to their support like painted walls, stone walls, and tree barks and help the climber conquer impossible spaces!

Buttress roots

Some trees like the Bombax ceiba have developed special root system where the base of the trees become like a fortress by increasing in their area which can make the tree stand firmly and. balance its own weight so that it stands firm in the soft, moist rainforest soil.

For special functions

Breathing roots

Trees that grow in a marshy and salty environment, the floor is often flooded with high tides have found some ingenious ways to help their roots get nitrogen. In soil often flooded with saltwater, it is impossible to get all the nitrogen required as there is no air in the soil. So the trees like Rhizophora have developed erect roots that grow upright from the underground roots having pores called “pneumatophores” which enable gas exchange.

Root nodules

In Legumes, the roots have developed some special structures called “nodes” or “nodules” to house nitrogen-fixing bacteria. These nitrogen-fixing bacteria fix the atmospheric nitrogen in the soil which are absorbed by the plants and the leftover nitrogen also contributes to increasing the soil fertility!

Aerial roots

Epiphytes like orchids have aerial roots as these plants grow on other trees and do not need any soil to grow. These epiphytic aerial roots contain absorbent tissue called “velamen” which helps the plant to absorb water and nutrients from the surrounding atmosphere.

These roots also hold the plant to its substrate like the Dendrobium on the right holds tightly to the tree it grows on. The roots serve two purposes here – holding the plant in place and getting it nutrients required.

Sucking roots

In some root parasites like the Sandal Tree (Santalum album), the plant develops special structures called haustoria which attach to the roots of its host plants and rob nutrients from it!

Floating roots

In some semi-aquatic plants like Ludwigia ascendens, some roots get modified into buoys and help the plant float on water. The roots have modified into spongy tissue with huge air spaces and make the plant float on the water surface.

Assimilatory roots

In climbers like Tinospora cordifolia, special roots called assimilatory roots are produced from the nodes which usually hang down from the plant like the prop roots of a banyan tree. These climbers usually climb onto a nearby tree and in some cases, the roots hanging down from the tree, from a distance, might confuse us for a banyan tree! Research suggests that these roots might be useful in CO2 assimilation in these plants.

Mycorrhizal roots

Temperate trees like Pinus especially has an interesting partnership with its fungal friends in the forest. They form an extensive network under the ground with fungal hyphae and use it to transfer food and nutrients from one tree to another. It was also found that these networks keep old stumps alive and also provide nutrients to the seedlings shaded by the mother trees.

Coralloid roots of Cycas

In Cycas, special roots called coralloid roots (These roots look like the sea corals. Hence the name ‘coral’loid) develops. These are apogeotropic i.e., coralloid roots grow towards the surface of the soil. They have a layer of cyanobacteria (blue-green algae) that fix nitrogen.

Reproductive roots

Some roots like Sweet potato and Dahlia can grow new plants. Hence they are called reproductive roots. They are used as excellent means for vegetative propagation of such plants.

Contractile or Pull roots

Plants like Canna, Crocus, Allium, Lilium, Haworthia have special roots called contractile roots which have the capability to contract and expand. In Haworthia, for example, the contractile roots help to pull the plant a bit under the soil surface during times of drought helping the plant to survive difficult times with less water loss.

Root Thorns

In some trees like Crysophila, the roots on the trunk get modified into sharp thorns which act as great protective agents!

Plants never cease to amaze us when it comes to adapting to the environment. They always find a solution when they face a problem and that solution is ingenious. This blog post is just a starter of how plants modify their one organ the ROOTS to suit their needs and to the changes in their environment. There is much more. Learn from plants to solve your problems that make you unique like every single plant out there! Love plants and stay curious!

There are two basically types of root system that are common in plants. They are, Tap Roots and Fibrous Roots.

The Tap Root System

The tap root is characterised by a big, strong anchor root that is a primary root for the plant. Several branches arise from the primary root and they are called as secondary roots and the secondary roots further branch to form the tertiary roots. The tertiary roots end up forming root hairs.

The taproot is advantageous in several ways. They are very helpful in anchoring the plants firmly to the soil and hence trees with tap roots can withstand storms at ease. They also go deep inside the soil and can help in absorbing ground water. This will be really helpful for the trees while there is a drought. The Tap Root System is a characteristic feature of the dicots.

The Fibrous Root System

The fibrous root system is a tuft of roots that arise from the base of the stem. They start as a taproot from the radicle after germination. The single root is soon replaced with a tuft of fibrous roots as the plant grows. These are characteristics of a monocot plant. The monocots are generally herbs and shrubs. The fibrous root enable them to hover over on the surface and extract the nutrients of the rich top-soil. Hence, they are mostly short lived except for the Palms which live for several years.

A root tip can be classified into four regions –

• Region of Maturation – The region of the root where the root hairs are present and is the mature part of the root. This is the region of the root where the growth has completed.
• Region of Elongation – The region of the root where the root grows in length. This region contains cells that rapidly elongating length-wise which results in increase of the root length.
• Region of Meristematic activity – This region is where the precursor (root meristems) cells are present. These cells continuously grow and get differentiated into other mature cells. This is the region of growth producing new cells.
• Root Cap – It can be seen covering the tip of the roots. The main job of the root cap is to protect the young meristematic cells. It also helps the roots to push against its odds in the soil like small stones.

The above diagram shows different regions of a root

Functions of the Root System

The root system as it is very important part of the plant has several functions. Some of the important functions that the root system perform are –

Holding the plant upright – The roots are the reason why the plants stand upright. They give enough mechanical strength that is required for the plant to stand straight so the shoot could grow in search of light and perform it’s activities normally.

Searching for new resources – The roots are almost on an endless search. They keep growing probing underground in search of water and nutrition. The tap roots of the fig trees are known to grow the longest roots. The Fig trees found on the Echo caves near Ohrigstad, Mpumalanga, South Africa have tap roots that go in search of water that is 400 feet underground inside the caves.

Photo credit: http://rideintobirdland.com

Another example is the lush and dense forests of the Yucatan peninsula. The Yucatan has great expanses of dense forests although there are no running rivers on it’s surface. The secret is underground inside the caves that hold fresh water. This fresh water supports those great forests. There are openings here and there which are called “cenotes”. The cenotes were an important water source for the Mayan people and they considered it sacred and used some of them to offer their sacrifices to their Gods.

The tree roots of the forests of Yucatan reach to the water underground for water.

Storage chambers – They serve as storage organs for the plants and the reserve food is used up by the plant during the unfavorable periods like periods of drought. Potato, tapioca, carrot, beetroot, sweet potatoes are all examples of storage roots. They not only serve as storage organs but also as resurrectors. Sometimes, the whole shoot of the plant can get eaten up by a herbivore. The underground storage however remains intact and the plant regrows from the storage roots and it is there again!

Underground warfare – Several species of plants are known to protect their territory well by defending themselves vigorously. They wage furious wars underground – a silent war – a chemical war! This helps the plant defeat it’s competitors thereby using up all the resources available for itself. The Spotted Knapweed – Centaurea maculosa, native to the Eastern Europe,is an invasive species in the US and a big problem. This plant wages an underground warfare where it roots release a toxin Catechin which inhibits the growth of several native plants and grasses. By doing this, it has invaded and occupied at least 4.5 million acres of land in Montana alone!

Ecologists tried several ways to control this land-hungry plant. They employed different ways like weedicides, bio-pests, sheep grazing but was not able to control this beast. Fortunately ecologists and botanists in Montana later found a plant (native to Montana) that could counter spotted knapweed’s chemical attack. It was the Lupine – Lupinus sericeus which also had a counter chemical attack against the Knapweed’s toxin. The lupins seem to release oxalic acid which not only counters the attack but also helps to protect the other native plants within the range of the Lupins.

Special functions – The roots are modified into special structures in many plants and trees that perform various functions like providing extra support to plants, enabling the plant breathe in swampy regions, help them absorb water and nutrients from the air in epiphytes and from other host plants in parasitic plants. The modifications of roots is so diverse that it deserves a separate post. So, I leave it here for now.

Economic Importance of Roots

• We consume several storage roots as food items. The roots are all make delicious dishes! Carrots, radishes, turnips, sugar beets, sweet potatoes, tapioca, Yams and much more. All these roots along with great recipes give delicious dishes.
• The Yam roots produce estrogen which are used in making birth control pills.
• Several plants store valuable chemicals in their roots which are used in different treatment methods worldwide. Ginseng, Clitoria ternatea, Aconitum, Gentiana lutea are used in medicine.
• Several Legume species have root nodules which host nitrogen fixing bacteria and are used in agricultural fields as great nitrogen enhancers.
• The roots hold the soil together and prevent it from erosion by various agents like wind and water. They also prevent landslides when more trees and plants are planted on steep slopes.
• The plants on desert sand dunes can help stabilize the sand dunes and thereby facilitating desert land reclamation.