Root

Warning: mkdir() [function.mkdir]: Permission denied in /home/webs/affiliatelib2/CacheManager.php on line 12

Warning: mkdir() [function.mkdir]: No such file or directory in /home/webs/affiliatelib2/CacheManager.php on line 12

Warning: fopen(/home/templatecore2cache//*cluesnet.com/37/37c7e91051103a3f8fe5edbd71488cb7788ee55e.tc2cache) [function.fopen]: failed to open stream: No such file or directory in /home/webs/affiliatelib2/CacheManager.php on line 130

Warning: fwrite(): supplied argument is not a valid stream resource in /home/webs/affiliatelib2/CacheManager.php on line 131

Warning: fclose(): supplied argument is not a valid stream resource in /home/webs/affiliatelib2/CacheManager.php on line 132

In vascular plants, the root is the organ of a plant body that typically lies below the surface of the soil (compare with plant stem). However, this is not always the case, since a root can also be aerial root (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 Node (botany). There are also important internal structural differences between stems and roots. The two major functions of roots are 1.) absorption of water and inorganic nutrients and 2.) anchoring the plant body to the ground. Roots also function in cytokinin synthesis, which supplies some of shoot needs. They often function in storage of food. The roots of most vascular plant species enter into symbiosis with certain fungi to form mycorrhizas, and a large range of other organisms including bacteria also closely associate with roots.

Root structure grown plantAt 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 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.

The outside surface of the primary root is the epidermis (botany). Recently produced epidermal cells absorb water from the surrounding environment and produce outgrowths called trichome#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 salinity is more difficult for most plant species to absorb.

Beneath the epidermis is the cortex, which comprises the bulk of the primary root. Its main function is storage of starch. Intercellular spaces in the cortex aerate cells for cellular respiration. An endodermis is a thin layer of small cells forming the innermost part of the cortex and surrounding the vascular tissues deeper in the root. The tightly packed cells of the endodermis contain a substance known as suberin in their cell walls. This suberin layer is the Casparian strip, which creates an impermeable barrier of sorts. Mineral nutrients can only move passively within root cell walls until they reach the endodermis. At that point, they must be actively transported across a cell membrane to continue further into the root. This allows the plant to accumulate mineral nutrients in the Stele (biology).

The vascular cylinder, or stele, consists of the cells inside the endodermis. The outer part, known as the pericycle, surrounds the actual Vascular tissue 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.

Secondary growth All roots have primary growth or growth in length. Roots of many vascular plants, especially dicots and gymnosperms, often undergo secondary growth, which is an increase in diameter. A vascular cambium forms in the stele to produce secondary phloem and secondary xylem. The epidermis is replaced by a periderm. As the stele increases in diameter, the cortex, pericycle and endodermis are lost. Even nonwoody roots often undergo secondary growth, including those of tomato and alfalfa.

Root growth plantsEarly root growth is one of the functions of the apical meristem located near the tip of the root. The meristem 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 Earth's atmosphere, mineral 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.

Growth from apical meristems is known as primary growth, which encompasses all elongation. Secondary growth encompasses all growth in diameter, a major component of woody plant tissues and many nonwoody plants. For example, storage roots of sweet potato have secondary growth but are not woody. 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.

In plants with secondary growth, the vascular cambium, originating between the xylem and the phloem, forms a cylinder (geometry) of tissue along the Plant 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).

At this point, the cork cambium begins to form the periderm, consisting of protective cork (material) cells containing suberin. In roots, the cork cambium originates in the pericycle, a component of the vascular cylinder. support a tree in very soft, wet soil conditions

The vascular cambium produces new layers of secondary xylem annually. The xylem vessels are dead at maturity but are responsible for most water transport through the vascular tissue in stems and roots.

Types of roots 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. It is the first part of the root to be originated. During its growth it rebranches to form the lateral roots. It usually grows downwards. Generally, two categories are recognized:

the taproot system: the primary root is prominent and has a single, dominant axis; there are fibrous secondary roots running outward. Usually allows for deeper roots capable of reaching low water tables. Most common in dicots. The main function of the taproot is to store food.
the diffuse root system: the primary root is not dominant; the whole root system is fibrous and branches in all directions. Most common in monocots. The main function of the fibrous root is to anchor the plant.

Specialized roots The roots, or parts of roots, of many plant species have become specialized to serve adaptive purposes besides the two primary functions described in the introduction.

Adventitious roots arise out-of-sequence from the more usual root formation of branches of a primary root, and instead originate from the stem, branches, leaves, or old woody roots. They commonly occur in monocots and pteridophytes, but also in many dicots, such as clover (Trifolium), ivy (Hedera), strawberry (Fragaria) and willow (Salix). Most aerial roots and stilt roots are adventitious. In some conifers adventitious roots can form the largest part of the root system.
Aerating roots (or pneumatophores): roots rising above the ground, especially above water such as in some mangrove genera (Avicennia, Sonneratia). In some plants like Avicennia the erect roots have a large number of breathing pores for exchange of gases.
Aerial roots: roots entirely above the ground, such as in ivy (Hedera) or in epiphyte orchids. They function as prop roots, as in maize or anchor roots or as the trunk in strangler fig.

Contractile roots: they pull bulbs or corms of monocots, such as hyacinth and lily, and some taproots, such as dandelion, deeper in the soil through expanding radially and contracting longitudinally. They have a wrinkled surface.
Coarse roots: Roots that have undergone secondary thickening and have a woody structure. These roots have some ability to absorb water and nutrients, but their main function is transport and to provide a structure to connect the smaller diameter, fine roots to the rest of the plant.
Fine roots: Primary roots usually

root from FOLDOC
root. 1. < operating system > The Unix superuser account (with user name "root" and user ID 0) that overrides file permissions. The term avatar is also used.

root directory from FOLDOC
root directory < file system > The topmost node of a hierarchical file system. (1996-11-21) Try this search on Wikipedia, OneLook, Google

Definition: root from Online Medical Dictionary
The Online Medical Dictionary is a searchable dictionary of definitions from medicine, science and technology.

BBC - Skillswise Words - Root words quiz
Quiz testing knowledge of word building, focusing on root words and how learning to recognise and understand them can help with spelling.

BBC - Skillswise Words - Root words factsheets
Factsheets about word building, focusing on root words and how learning to recognise and understand them can help with spelling.

Legal Recruitment Specialists Taylor Root: Legal jobs
Legal Recruitment Experts Taylor Root. Search UK Legal Jobs, Law Careers ... Taylor Root is the world’s leading legal recruitment firm, with offices throughout the UK, the Far ...

Root - Wikipedia, the free encyclopedia
In vascular plants, the root is the organ of a plant body that typically lies below the surface of the soil. However, this is not always the case, since a root can also be aerial ...

Golden Root Complex - Herbal Blue Pill Alternative
The natural herbal blue pill. Guaranteed results with this revolutionary new pill or your money back. Buy Golden Root with us at the lowest prices on the web.

Welcome | Root & Branch
We've just updated our newsletter mailing list system. If you're a newsletter subscriber, you should have received an email asking you to confirm you're subscribing to the new ...

The ROOT System Home Page
An object oriented framework for large scale data analysis. ROOT is a C++ replacement of the popular PAW program developed at CERN.