Aerial roots are the adventitious roots that grow above the surface of the ground and are classified into four different categories, namely, Prop roots, Pneumatophores, Haustorial roots, and Propagative roots. Prop roots (stranglers), a subtype of aerial roots, develop from the horizontal branches of the aerial plant. These are hygroscopic roots and can obtain water from the atmosphere. They develop in a downward direction and, once they reach the ground they penetrate into the ground to support the tree. These roots contain root caps on their tips, which helps them to form thick structures. This provides them pillar-like appearance. It becomes difficult to distinguish between the trunk root and the prop root because of their thickness. All prop roots are aerial roots, but all aerial roots are not prop roots. Examples of prop roots are, Ficus benghalensis (Banyan tree), India-rubber tree, Corn, etc.
Examples of Prop roots
1. Ficus elastica
Ficus elastica, also known as rubber fig/rubber plants, belongs to the Moraceae family. In its natural environment, it normally grows up to 55 meters. Ficus elastica produces a milky white latex, that was formerly used to make rubber. This produces latex is irritant to the eyes and skin, and is toxic if consumed. This plant is highly tolerant to drought, but prefers remaining in moisture, humid and tropical conditions. Its cultivation is preferred in bright light but not in high temperatures. The taxonomic tree of ficus elastica is shown below-
2. Ficus benghalensis
Ficus benghalensis is a scientific name for banyan trees and it belongs to the Moraceae family. These plants are toxic to humans and pets. All the parts of the plant contain a highly irritant sap and consumption of any part of the plant may cause throat irritation, drooling, and vomiting. It is mainly found in monsoons and rainforests and can reach a height of up to 30 meters. The roots grow downwards, like lianas, as aerial roots on the branches. India has the largest giant banyan trees all over the world and the notable ones are, Thimmamma Marrimanu, Kabirvad, and The great banyan. These trees can reach a height of up to 30 meters, and spread laterally indefinitely.
3. Red mangroves
Red mangroves, scientifically known as Rhizophora mangle, are broad-leaved evergreen trees that are easily remarkable with their above-ground prop roots and viviparous seeds. Red mangroves belong to the Rhizophoraceae family. Red mangroves are sometimes also called “walking trees” because their continuously growing prop roots make them look like they are walking on water. In tropical regions, they can grow up to 80 feet in height. The prop roots of red mangroves help to support the plant in soft swamp soil. Red mangroves have edible fruits, but they are bitter in taste.
4. Ficus macrophylla
Ficus macrophylla, also known as Moreton Bay fig or Australian banyan, is an evergreen banyan tree that belongs to the Moraceae family. Until the roots of ficus macrophylla establish contact with the ground, its seedling lives as an epiphyte. When it enlarges and strangles its host, it eventually becomes a freestanding tree by itself and mainly blooms in Spring, Summer, and Autumn.
Pandanus is the scientific name of screwpine and it belongs to the Pandanaceae family. They are capable of reaching 60 feet but are found only 20-30 feet in height. Screwpines are found mostly in Asia, Africa, and Oceania. Screwpine uses involve the flavoring of jams and chutneys. They can also be used to make a paste that can be used in cakes and desserts. Wrapping of savoury dishes, such as chicken and sticky rice, is also done through screwpines.
The corn plant, also known as maize, is a cereal plant that is related to grass, and the scientific name of this plant is Zea mays. Sweeteners, flour (corn meal), oil, starch, animal feed, biodegradable plastics, and ethanol (a fuel additive) all are made from corn. The stem of this plant is very tall and is usually supported by numerous prop roots which are extending out from the stem’s base. Prop roots in corn plants play a significant role by providing structural support to the plant. In this, the prop roots do not function to absorb water and nutrients, instead, the stem of the plant gets attached more firmly to the soil to absorb water and nutrients.