ROOT: CHARACTERISTICS, PARTS, STRUCTURE, FUNCTIONS AND TYPES - BIOLOGY - 2025

The root is the organ of the plant that is frequently located underground, since it presents positive geotropism. Its main function is the absorption of water, inorganic nutrients and the fixation of the plant to the soil. The anatomical structure of the roots can be variable, but simpler than that of the stem, since it lacks nodes and leaves.

The root is the first embryonic structure that develops from the germination of the seed. The radicle is an initially poorly differentiated structure that will give rise to the primary root covered by the caliptra, which acts as an apical protector.

Estate. Source: pixabay.com

The main axis of the plants is constituted by the stem and the root. The union of both structures does not present an obvious differentiation, since the vascular tissues are included in the fundamental tissue.

The morphology of the root is simpler due to its habitat under the ground. In the roots there is no presence of knots, buds, stomata, or chlorophyll production, with some exceptions of roots adapted to special conditions.

This structure is responsible for the absorption and transport of water and nutrients stored in the soil. The absorbent hairs capture these elements - raw sap -, which are transported to the foliar area where they are transformed in the photosynthesis process.

Likewise, the roots hold the plants to the ground, preventing their detachment by external agents. In other cases, the roots act as storage or reserve structures for nutritional elements, for example, sweet potatoes, beets, carrots or cassava.

General characteristics

Roots of different morphology and size. Source: pixabay.com

- The roots are structures of underground growth.

- It does not present development of buds, nodes, internodes and leaves.

- They show indefinite growth, subject to the conditions and structure of the soil.

- Positive geotropism, that is, growth acts in favor of the force of gravity.

- They present radial symmetry or radial growth pattern; It is made up of concentric rings or layers of differentiated tissues.

- Function of anchoring and absorption of ascending sap or raw sap.

- They have the ability to maintain symbiotic relationships with microorganisms present in the rhizosphere of the soil.

- They present a varied morphology and diversity of sizes.

- They can be primary, secondary and adventitious.

- Some are epigeas -above the ground-, or aerial -above the ground or water-.

- According to the environment where they develop, it can be terrestrial, aquatic and aerial.

- Some roots provide health benefits, as they have medicinal properties.

- They are a source of food for animals and man.

- They have various properties, which allows them to be used in pharmaceuticals, cosmetics and food additives.

- The roots of various species promote the protection and conservation of the soil.

- The agglomeration of roots allows the material that constitutes the soil to be sustained, thus preventing the wind and water from eroding it.

- To penetrate the ground, the root has a specialized structure called piloriza, cap or caliptra.

- The caliptra has the function of protecting the root growth area.

- The root is made up of the following fundamental tissues: epidermis, cortical parenchyma and vascular tissue.

Root parts

Cap or caliptra

Outer covering wrap that protects the root tip and contributes to penetration into the soil. It originates from the dermatogen and derived meristem protodermis -dicotyledons-, or from the kalliptrogen -monocotyledons-.

Caliptra is made up of cells with an abundant content of starch and dictyosomes, as well as mucilages that favor the advance of the root in the soil. Its function is basically the protection of the meristematic zone.

Root zones. Source: Racine4.jpg: Cehagenmerakderivative work: CASF).push ({});

Marrow

Tissue made up of parenchyma, usually partially or totally clears, or disappears forming a hollow or fistulous root.

Features

Support

Root support function. Source: pixabay.com

The roots are the organ par excellence in charge of fixing or anchoring the plant to the ground. They prevent the plant from being blown away by wind or rain, and provide a firm foundation for solid growth.

Transport

Through the roots, the absorption of water and nutrients dissolved in the soil occurs. The pressure exerted by the absorption of water through the roots speeds up the transport of nutrients to the rest of the plant.

Storage

The soil is the place of storage or accumulation of nutritive elements necessary for the growth and development of plants. In fact, it is the support for fertilizer and organic matter from compost or plant waste.

Symbiosis

The rhizosphere or area around the roots constitutes the place where various symbiotic associations develop between soil microorganisms -mycorrhizae, fungi, bacteria-.

These associations favor the dissolution of soil phosphorus, the fixation of atmospheric nitrogen, and the development and growth of secondary roots.

Soil formation

The roots have the property of secreting powerful organic acids capable of breaking down the limestone that make up the soil. In this way, mineral molecules are released, which together with the enzymes secreted by the roots and the symbiotic associations promote the production of humus.

Protection

The accumulation and development of a compact mass of roots contributes to the support or firmness of the soil. In this way, water erosion and wind erosion are prevented.

Communication

There is evidence of the contact that certain tree species have through the roots or mycorrhizal tissue of the soil in order to share water and nutrients. This communication is essential for a tree to overcome erosion problems, physical damage or pest attacks.

Types

Depending on their origin, the roots can be pivoting or adventitious. The pivoting ones originate from the radicle of the embryo, while the adventitious ones originate from any organ of the plant.

In monocots, the embryonic root has a relatively short life, being replaced by the adventitious roots that are born from the stem. In dicots the root is pivoting with the main axis more thickened and they are long-lived.

According to the morphology the roots are classified as:

Axonomorphic

It is a taproot type with few underdeveloped secondary roots.

Branched

The main root is profusely divided, forming after secondary roots.

Fasciculated

It is made up of a bundle or bunch of secondary roots that have the same thickness or size.

Tuberous

Roots with a fasciculate structure that present thickening due to the accumulation of nutritional and reserve substances. The bulbs, corms, rhizomes and tubers are tuberous roots.

Napiform

Root thickened by the accumulation and storage of reserve substances. Some napiform roots are turnip (Brassica rapa) and carrot (Daucus carota).

Tabular

The tabular root is formed from the base of the trunk forming. It has the function of an accessory to fix the plant in the soil and contains pores that allow the absorption of oxygen.

Adaptations

According to the adaptations that the roots present to the conditions of the environment where they develop, the following specialized types are found:

Aerial roots

Aerial roots. Source: pixabay

Common root of epiphytic plants such as bromeliads, orchids, ferns, and mosses. It is characterized by presenting a specialized rhizodermis called canopy that absorbs moisture from the air, prevents moisture loss and acts as a mechanical protection.

Support roots

They are observed in some grasses such as corn. They are adventitious roots formed from the nodes of the stem that have the function of fixing the stem to the ground, and absorbing water and nutrients.

Strangling roots

Parasitic roots of plants that grow on a tree, causing death because the host is unable to grow and develop. The banyan or banyan tree (Ficus benghalensis) is an example of a plant with strangler roots.

Haustorials

They are the roots of parasitic and hemiparasitic plants that absorb water and nutrients from their hosts through a specialized haustorium that penetrates the conductive bundles.

Pneumatophores or aeration roots

Common plants that inhabit mangroves, have negative geotropism and have the function of gas exchange with the environment.

Tuberous

Carrot. Source: pixabay.com

They present a particular thickening caused by the storage of reserve substances at the level of the parenchymal tissue. It is common to cassava (Manihot esculenta) and carrot (Daucus carota).

Tabular roots

It is a support root that acts by increasing the fixation of the tree to the ground, in addition to contributing to the aeration of the plant. Characteristic of a large endemic tree of the Cordillera de la Costa in Venezuela called Gyranthera caribensis.

References

1. Visual Atlas of Science (2006) Planas. Editorial Sol 90. 96 pp. ISBN 978-84-9820-470-4.
2. Dubrovsky Joseph G. and Shishkova Svetlana (2007) Enigmas of the root: the hidden part of the plant. Biotechnology V14 CS3.indd. 12 pp.
3. García Breijo Francisco J. (2015) Item 6. The root. Primary Structure and Modifications. Agroforestry Ecosystems Department. Higher Technical School of Rural Areas and Oenology. Polytechnic university of Valencia.
4. González Ana María (2002) Topic 20. Anatomy of the Root. Morphology of Vascular Plants. Recovered at: biologia.edu.ar
5. The Root of Plants: Morphology and Primary Structure (2018) Universidad Nacional de la Plata. Faculty of Agricultural and Forest Sciences. Plant Morphology Course. 33 pp.
6. Megías Manuel, Molist Pilar & Pombal Manuel A. (2018) Plant Organs: Root. Atlas of Plant and Animal Histology. Department of Functional Biology and Health Sciences. Faculty of Biology. University of Vigo.
7. Root (botany) (2019) Wikipedia, The Free Encyclopedia. Recovered in: Date of consultation: wikipedia.org
8. Valla, Juan J. (1996) Botany. Morphology of superior plants. Southern Hemisphere Editorial. 352 pp. ISBN 9505043783.