root

The external anatomy of a typical flowering plant.

Types of root. Many flowers (dandelion) and vegetables (carrot) have swollen tap roots with smaller lateral roots. The tuberous roots of the cassava are swollen parts of an underground stem modified to store food. The fibrous roots of the grasses are all of equal size. Prop roots grow out from the stem and then grow down into the ground to support a heavy plant. Aerial roots grow from stems but do not grow into the ground; many absorb moisture from the air.

Water is absorbed from the soil by the root hair cells and then travels through the xylem to the plant's leaves. The root hair cells give the root a large surface area through which to absorb water.

The part of a plant that is usually underground, and whose primary functions are anchorage and the absorption of water and dissolved mineral salts. Roots usually grow downwards and towards water (that is, they are positively geotropic and hydrotropic; see tropism). Plants such as epiphytic orchids, which grow above ground, produce aerial roots that absorb moisture from the atmosphere. Others, such as ivy, have climbing roots arising from the stems, which serve to attach the plant to trees and walls.

The absorptive area of roots is greatly increased by the numerous slender root hairs formed near the tips. A calyptra, or root cap, protects the tip of the root from abrasion as it grows through the soil.

Symbiotic associations occur between the roots of certain plants, such as clover, and various bacteria that fix nitrogen from the air (see nitrogen fixation). Other modifications of roots include contractile roots, pneumatophores, taproots, and prop roots.

root

Of an equation, a value that satisfies the equality. For example, x = 0 and x = 5 are roots of the equation x² −5x = 0.

root

In language, the basic element from which a word is derived. The root is a morpheme, a unit that cannot be subdivided. The Latin word dominus (‘master’), for example, is a root from which many English words are derived, such as ‘dominate’, ‘dominion’, and ‘domino’.

root

A chord in root position on C. The second diagram shows first and second inversions. According to this theory, which takes no account of the different functions of chords, a four-note chord has three possible inversions, and so on.

In music, in a chord, the tonic note from which the other notes are derived. For example, in a chord consisting of any spacing or arrangement of the notes C–E–G, C is always the root. A chord is considered to be in ‘root position’ when the root is the lowest voice or part, usually in the bass.

root

In computing, the account used by system administrators and other superusers in Unix systems. Users logged in as root (or in some systems, avatar) have permission to access and change all the files in the system.

root

In mathematics, a number which when multiplied by itself will equal a given number (the inverse of an exponent or power). On a calculator, roots may be found by using the buttons marked or inv xy. For example, the cubed root of 27 is found by pressing 27, then inv xy, then 3.