In vascular plants, the root is that organ of a plant body that typically lies below the surface of the soil (compare with stem). However, this is not always the case, since a root can also be aerial (that is, growing above the ground) or aerating (that is, growing up above the ground or especially above water). On the other hand, a stem normally occurring below ground is not exceptional either (see rhizome). So, it is better to define root as a part of a plant body that bears no leaves, and therefore also lacks nodes. The two major functions of roots are 1) absorption of water and inorganic nutrients and 2) anchoring the plant body to the ground. Divisions Non-seed-bearing plants Equisetophyta Lycopodiophyta Psilotophyta Pteridophyta Superdivision Spermatophyta Pinophyta Cycadophyta Ginkgophyta Gnetophyta Magnoliophyta The vascular plants are those plants that have specialized cells for conducting water and sap within their tissues, including the flowering plants, conifers and other gymnosperms, but not mosses, algae, and the like (nonvascular... Divisions Green algae land plants (embryophytes) non-vascular embryophytes Hepatophyta - liverworts Anthocerophyta - hornworts Bryophyta - mosses vascular plants (tracheophytes) seedless vascular plants Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongue ferns seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering... For the heavy metal band see Soil (band) Soil is the layer of minerals and organic matter, in thickness from centimetres to a metre or more, on the land surface. ... A stem is the above ground axis of a vascular plant. ... In botany, a rhizome is a horizontal, usually underground stem of a plant that often sends out roots and shoots from its nodes. ... A node is the place on a stem where a lateral meristem develops as either a lateral bud or a secondary shoot, often subtended by a leaf. ...

Primary and secondary roots in a cotton plant

Primary and secondary roots. ... Primary and secondary roots. ...

Root structure

At the tip of every growing root is a conical covering of tissue called the root cap. It usually is not visible to the naked eye. It consists of undifferentiated soft tissue (parenchyma) with unthickened walls covering the apical meristem. The root cap provides mechanical protection to the meristem cells as the root advances through the soil, its cells worn away but quickly replaced by new cells generated by cell division within the meristem. The root cap is also involved in the production of mucigel, a sticky mucilage that coats the new formed cells. These cells contain statoliths, starch grains that move in response to gravity and thus control root orientation. Meristem is a type of embryonic tissue in plants consisting of unspecialized, youthful cells called meristematic cells and found in areas of the plant where growth is or will take place, this is in roots and shoots. ...

The outside surface of a root is the epidermis. Recently produced epidermal cells absorb water from the surrounding environment and produce outgrowths called root hairs that greatly increase the cell's absorptive surface. Root-hairs are very delicate and generally short-lived, remaining functional for only a few days. However, as the root grows, new epidermal cells emerge and these form new root hairs, replacing those that die. The process by which water is absorbed into the epidermal cells from the soil is known as osmosis. For this reason, water that is saline is more difficult for most plant species to absorb. Trichomes, from the Greek meaning growth of hair, are fine outgrowths or appendages on plants and protists. ... Osmosis is the diffusion of a solvent through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration. ... Salinity is the saltiness or dissolved salt content of a body of water. ...

Beneath the epidermis is the cortex, which comprises the bulk of the root. Its main function is storage of starch. Intercellular spaces in the cortex aerate cells for respiration. An endodermis is a thin layer of small cells forming the innermost part of the cortex and surrounding the vascular tisues deeper in the root. The tightly packed cells of the endodermis contain a substance known as suberin and create an impermeable barrier of sorts. Water can only flow in one direction through the endodermis: in towards the center of the root, rather than outward from the stele to the cortex. Starch is a complex carbohydrate which is insoluble in water. ... Cellular respiration is, in its broadest definition, the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. ... Endodermis is the bottom layer of skin. ... Suberin is a waxy substance found in higher plants. ...

The vascular cylinder or stele consists of the cells inside the endodermis. The outer part, known as the pericycle, surrounds the actual vascular tissue. In monocotyledonous plants, the xylem and phloem cells are arranged in a circle around a pith or center, whereas in dicotyledons, the xylem cells form a central "hub" with lobes, and phloem cells fill in the spaces between the lobes. In a vascular plant, the stele is the central part of the root or stem containing the vascular tissue. ... Vascular is an adjective for the word vessel and refers to tube-like structures. ... Orders Base Monocots: Acorus Alismatales Asparagales Dioscoreales Liliales Pandanales Family Petrosaviaceae Commelinids: Arecales Commelinales Poales Zingiberales Family Dasypogonaceae Monocotyledons or monocots are a group of flowering plants usually ranked as a class and once called the Monocotyledoneae. ... Categories: Plant physiology | Trees | Biology stubs ... In vascular plants, phloem is the tissue that carries organic nutrients, particularly sucrose. ... The centre dark spot (about 1 mm diameter) in this yew wood is the pith Pith is a light substance that is found in vascular plants. ... Orders see text Dicotyledons or dicots are flowering plants whose seed contains two embryonic leaves or cotyledons. ...

Root systems of prairie plants

Download high resolution version (500x795, 83 KB)Root system Downloaded from : [[1]] Credits : US Environmental Protection Agency File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Download high resolution version (500x795, 83 KB)Root system Downloaded from : [[1]] Credits : US Environmental Protection Agency File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... A prairie is an area of land of low topographic relief that principally supports grasses and herbs, with few trees, and is generally of a mesic (moderate or temperate) climate. ...

Root growth

Early root growth is a function of the apical meristem located near the tip of the root. The merstem cells more or less continuously divide, producing more meristem, root cap cells (these sacrificed to protect the meristem), and undifferentiated root cells. The latter will become the primary tissues of the root, first undergoing elongation, a process that pushes the root tip forward in the growing medium. Gradually these cells differentiate and mature into specialized cells of the root tissues.

Roots will generally grow in any direction where the correct environment of air, nutrients and water exists to meet the plant's needs. Roots will not grow in dry soil. Over time, given the right conditions, roots can crack foundations, snap water lines, and lift sidewalks. At germination, roots grow downward due to gravitropism, the growth mechanism of plants that also causes the shoot to grow upward. In some plants (such as ivy), the "root" actually clings to walls and structures; this is known as thigmotropism, or response to touch. This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Nutrients and the body A nutrient is any element or compound necessary for or contributing to an organisms metabolism, growth, or other functioning. ... Drinking water This article focuses on water as we experience it every day. ... In a botanical sense, germination is the process of emergence of growth from a resting stage. ... Gravitropism is movement of a plant based on gravity. ... Species See text Hedera, English name Ivy (plural, Ivies), is a genus of about 10 species of climbing or ground-creeping evergreen woody plants in the Araliaceae, native in the Atlantic Islands, Europe, North Africa and across Asia east to Japan. ... Thigmotropism is the directional response of a plant organ to touch or physical contact with a solid object. ...

Most plants experience growth only along the apical meristems; this is known as primary growth, which encompasses all vertical growth. On the other hand, secondary growth encompasses all lateral growth, a major component of woody plant tissues. Secondary growth occurs at the lateral meristems, namely the vascular cambium and cork cambium. The former forms secondary xylem and secondary phloem, while the latter forms the periderm, found only in woody plants. A woody plant is any vascular plant that has a perennial woody stem -- that is, one that supports continued vegetative growth above ground from year to year. ... Vascular cambium is a tissue found in the stems of perennial dicots. ... Cork cambium is a tissue found in the stems of perennial dicots. ... Periderm is a layer of plant tisses dervived from the cork cambium, replacing the epidermis. ...

In woody plants, the vascular cambium, originating between the xylem and the phloem, forms a cylinder of tissue along the stem and root. The cambium layer forms new cells on both the inside and outside of the cambium cylinder, with those on the inside forming secondary xylem cells, and those on the outside forming secondary phloem cells. As secondary xylem accumulates, the "girth" (lateral dimensions) of the stem and root increases. As a result, tissues beyond the secondary phloem (including the epidermis and cortex, in many cases) tend to be pushed outward and are eventually "sloughed off" (shed). The word cylinder has several meanings. ... In common parlance, a stem is any elongated, usually narrow, extension or supporting structure of an object. ...

At this point, the cork cambium (noting that this process only occurs in woody plants) begins to form the periderm, consisting of protective cork cells containing suberin. In roots, the cork cambium originates in the pericycle, a component of the vascular cylinder. A cork stopper for a wine bottle Cork material is a subset of generic cork tissue, harvested for commercial use primarily from the Cork oak tree, Quercus suber, with Portugal producing most cork worldwide. ...

The vascular cambium produces new layers of secondary xylem annually. This dead tissue is responsible for most water transport through the vascular tissue (systems and roots).

Types of roots

Stilt roots in the Amazon Rainforest support a tree in very soft, wet soil conditions

See also taproot, fibrous root system and stolon. Download high resolution version (1024x768, 233 KB)air roots in the Amazon rainforest Tree roots captured on a small river in Salinas - Pará - Brazil Photographer: cesarpb Source: Stock. ... Download high resolution version (1024x768, 233 KB)air roots in the Amazon rainforest Tree roots captured on a small river in Salinas - Pará - Brazil Photographer: cesarpb Source: Stock. ... A river in the Amazon rainforest The Amazon is a rainforest in South America. ... A plants taproot is a straight tapering root that grows vertically down. ... A fibrous root system (sometimes also called adventitious root system) is the opposite of a tap root system. ... A stolon is an aerial shoot from a plant with the ability to produce adventitious roots and new offshoots of the same plant. ...

A true root system consists of a primary root and secondary roots (or lateral roots).

The primary root originates in the radicle of the seedling. During its growth it rebranches to form the lateral roots. Generally, two categories are recognized: In botany, the radicle is the first part of a seedling (a growing plant embryo) to emerge from the seed during germination. ...

• the taproot: the primary root is prominent and has a single, dominant axis; there are fibrous secondary roots running outward.
• the primary root is not dominant: the whole root system is fibrous and branches in all directions.

Adventitous roots arise from the stem and not from another root. They usually occur in monocots and pteridophytes, but also in a few dicots, such as strawberry (Fragaria vesca) and white clover (Trifolium repens). A plants taproot is a straight tapering root that grows vertically down. ... Orders Base Monocots: Acorus Alismatales Asparagales Dioscoreales Liliales Pandanales Family Petrosaviaceae Commelinids: Arecales Commelinales Poales Zingiberales Family Dasypogonaceae Monocotyledons or monocots are a group of flowering plants usually ranked as a class and once called the Monocotyledoneae. ... Orders see text Dicotyledons or dicots are flowering plants whose seed contains two embryonic leaves or cotyledons. ... Species see text The strawberry (Fragaria) is a genus of plants in the family Rosaceae (Rose Family), and the fruit of these plants. ... Binomial name Trifolium repens L. White Clover (Trifolium repens) is a species of clover native to Europe, North Africa, and West Asia. ...

Specialized roots

Aerating roots of a mangrove

• Aerating roots (or pneumatophores): roots rising above the ground, especially above water such as in some mangrove genera (Avicennia, Sonneratia)
• Aerial roots: roots entirely above the ground, such as in ivy (Hedera helix) or in epiphytic orchids. They function as prop roots or anchor roots.
• Contractile roots: they pull bulbs or corms of monocots deeper in the soil through expanding radially and contracting longitudinally. They show a wrinkled surface.
• Haustorial roots: roots of parasitic plants that can absorb water and nutrients from another plant, such as in mistletoe (Viscum album) and Rafflesia.
• Proteoid roots or cluster roots: dense clusters of rootlets of limited growth that develop under low phosphate or low iron conditions in plants from the following families Betulaceae, Casuarinaceae, Eleagnaceae, Moraceae, Fabaceae and Myricaceae.
• Stilt roots : these are adventitious support roots, common among mangroves. They grow down from lateral branches, branching in the soil.
• Storage roots : these roots are modified for storage of nutrients, such as carrots and beets
• tubiferous roots : forms rounded knobs (tuber) for food storage, such as the potato.

Mangrove swamp, partly underwater image showing the root system. ... Mangrove swamp, partly underwater image showing the root system. ... Above and below water view at the edge of the mangal Mangroves are woody trees or shrubs that grow in mangrove habitats or mangal (Hogarth, 1999). ... Above and below water view at the edge of the mangal Mangroves are woody trees or shrubs that grow in mangrove habitats or mangal (Hogarth, 1999). ... Species See text Hedera, English name Ivy (plural, Ivies), is a genus of about 10 species of climbing or ground-creeping evergreen woody plants in the Araliaceae, native in the Atlantic Islands, Europe, North Africa and across Asia east to Japan. ... An example of an epiphyte assemblage of orchids and bromeliads in a garden setting The term epiphyte refers to any plant that grows upon or attached to another living plant. ... Orchid re-directs here; for alternate uses see Orchid (disambiguation) Genera Over 800 See List of Orchidaceae genera. ... Orders Base Monocots: Acorus Alismatales Asparagales Dioscoreales Liliales Pandanales Family Petrosaviaceae Commelinids: Arecales Commelinales Poales Zingiberales Family Dasypogonaceae Monocotyledons or monocots are a group of flowering plants usually ranked as a class and once called the Monocotyledoneae. ... Species see text Mistletoe attached to eucalyptus host European mistletoe attached to a Silver Birch. ... Species Rafflesia arnoldi Rafflesia cantleyi Rafflesia gadutensis Rafflesia hasseltii Rafflesia keithii Rafflesia kerrii Rafflesia manillana Rafflesia micropylora Rafflesia patma Rafflesia pricei Rafflesia rochussenii Rafflesia schadenbergiana Rafflesia speciosa Rafflesia tengku-adlinii Rafflesia tuan-mudae Rafflesia is a genus of parasitic flowers. ... In chemistry, a phosphate is a polyatomic ion or radical consisting of one phosphorus atom and four oxygen. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metal Group, Period, Block 8 (VIIIB), 4 , d Density, Hardness 7874 kg/m3, 4. ... Genera Alnus - Alders Betula - Birches Betulaceae, or the Birch Family, includes two genera of trees and shrubs, the birches and the alders. ... Genera Allocasuarina Casuarina Gymnostoma Casuarinaceae is a family of dicotyledonous flowering plants placed in the order Fagales, consisting of 3 or 4 genera and approximately 70 species of trees and shrubs native to the Old World tropics (Indo-Malaysia), Australia, and the Pacific islands. ... Genera Antiaris Artocarpus - Breadfruit, Jackfruit Brosimum Broussonetia - Paper Mulberry Castilloa Cecropia Chlorophora Dorstenia Ficus - Fig, Banyan Maclura - Osage-orange Morus - Mulberry Musanga Pseudolmedia Streblus Treculia The flowering plant family Moraceae (Mulberry family) comprises some 40 genera and over 1000 species of plants widespread in tropical and subtropical regions, less common... Subfamilies Faboideae Caesalpinioideae Mimosoideae References GRIN-CA 2002-09-01 The Family Fabaceae (also as Family Leguminosae) is a grouping of plants in the Order Fabales, and one of the largest families of flowering plants with 650 genera and over 18,000 species. ... Binomial name Daucus carota The carrot is a root vegetable, typically orange or white in color with a woody texture. ... Binomial name Beta vulgaris L. The beet is a plant with a rounded fleshy taproot. ... A tuber is a part of a rhizome thickened for use as a storage organ, usually, though not always, subterranean, such as a potato. ... Binomial name Solanum tuberosum L. The potato (Solanum tuberosum) is a perennial plant of the Solanaceae, or nightshade, family, grown for its starchy tuber. ...

See also

• Rhizophilous - organisms which thrive in a proximity or in a symbiotic relationship with plant roots.
• Mycorrhiza - root symbiosis in which individual hyphae extending from the mycelium of a fungus colonize the roots of a host plant.

A mycorrhiza (typically seen in the plural form mycorrhizae meaning fungus roots) is a distinct type of root symbiosis in which individual hyphae extending from the mycelium of a fungus colonize the roots of a host plant. ...

References

• Brundrett M. C. (2002). Coevolution of roots and mycorrhizas of land plants. New phytologist 154(2): 275-304. (Available online: DOI  (http://dx.doi.org/10.1046/j.1469-8137.2002.00397.x) | Abstract (http://www.blackwell-synergy.com/links/doi/10.1046/j.1469-8137.2002.00397.x/abs/) | Full text (HTML) (http://www.blackwell-synergy.com/links/doi/10.1046/j.1469-8137.2002.00397.x/full/) | Full text (PDF) (http://www.newphytologist.org/Brundrett.pdf))
• R. Chen, E. Rosen, P. H. Masson (1999). Gravitropism in Higher Plants. Plant Physiology 120 (2): 343-350. (Available online: Full text (HTML) (http://www.plantphysiol.org/cgi/content/full/120/2/343) | Full text (PDF) (http://www.plantphysiol.org/cgi/reprint/120/2/343.pdf)) - article about how the roots sense gravity.
• Lynn Clark (2004). Primary Root Structure and Development (http://www.eeob.iastate.edu/classes/bot404/docs/404root104.pdf) - lecture notes
• J. A. Raven, D. Edwards (2001). Roots: evolutionary origins and biogeochemical significance. Journal of Experimental Botany 52 (Suppl 1): 381-401. (Available online: Abstract  (http://jxb.oupjournals.org/cgi/content/abstract/52/suppl_1/381) | Full text (HTML) (http://jxb.oupjournals.org/cgi/content/full/52/suppl_1/381) | Full text (PDF) (http://jxb.oupjournals.org/cgi/reprint/52/suppl_1/381.pdf))

External link

• Introduction to Botany - University of Arkansas (http://www.ualr.edu/~botany/roots.html)