root botany


  • Specialized[edit] Stilt roots of maize plant Cross section of an adventitous crown root of pearl millet (Pennisetum glaucum) Roots forming above ground on a cutting of an
    Odontonema (“Firespike”) Aerating roots of a mangrove The growing tip of a fine root Aerial root The stilt roots of Socratea exorrhiza Visible roots The roots, or parts of roots, of many plant species have become specialized to serve adaptive
    purposes besides the two primary functions[clarification needed], described in the introduction.

  • In order to escape shade, plants adjust their root architecture, most notably by decreasing the length and amount of lateral roots emerging from the primary root.

  • • Dimorphic root systems: roots with two distinctive forms for two separate functions • Fine roots: typically primary roots
    <2 mm diameter that have the function of water and nutrient uptake.

  • Where conditions are close to optimum in the surface layers of soil, the growth of surface roots is encouraged and they commonly become the dominant roots.

  • When a plant is under dense vegetation, the presence of other vegetation nearby will cause the plant to avoid lateral growth and experience an increase in upward shoot, as
    well as downward root growth.

  • [clarification needed] Ranunculus root cross section Perhaps the most striking characteristic of roots that distinguishes them from other plant organs such as stem-branches
    and leaves is that roots have an endogenous[5] origin, i.e., they originate and develop from an inner layer of the mother axis, such as pericycle.

  • 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.

  • The roots of most vascular plant species enter into symbiosis with certain fungi to form mycorrhizae, and a large range of other organisms including bacteria also closely
    associate with roots.

  • Adventitious root formation is enhanced in many plant species during (partial) submergence, to increase gas exchange and storage of gases like oxygen.

  • With this complex manipulation of Auxin transport in the roots, lateral root emergence will be inhibited in the roots and the root will instead elongate downwards, promoting
    vertical plant growth in an attempt to avoid shade.

  • For example, a root system that has developed in dry soil may not be as efficient in flooded soil, yet plants are able to adapt to other changes in the environment, such as
    seasonal changes.

  • The phytochrome PhyA that senses this Red to Far Red light ratio is localized in both the root system as well as the shoot system of plants, but through knockout mutant experimentation,
    it was found that root localized PhyA does not sense the light ratio, whether directly or axially, that leads to changes in the lateral root architecture.

  • The roots from one side of a tree usually supply nutrients to the foliage on the same side.

  • [41] Since nearby plants showed no changes in stomatal aperture researchers believe the drought signal spread through the roots and soil, not through the air as a volatile
    chemical signal.

  • These roots may be short lived, but are replaced by the plant in an ongoing process of root ‘turnover’.

  • [26] Once inhibited, auxin levels will be low in areas where lateral root emergence normally occurs, resulting in a failure for the plant to have the emergence of the lateral
    root primordium through the root pericycle.

  • [1] They are most often below the surface of the soil, but roots can also be aerial or aerating, that is, growing up above the ground or especially above water.

  • This system can be extremely complex and is dependent upon multiple factors such as the species of the plant itself, the composition of the soil and the availability of nutrients.

  • [40] Plant interactions Plants can interact with one another in their environment through their root systems.

  • [36] The evolutionary development of roots likely happened from the modification of shallow rhizomes (modified horizontal stems) which anchored primitive vascular plants combined
    with the development of filamentous outgrowths (called rhizoids) which anchored the plants and conducted water to the plant from the soil.

  • Studies have demonstrated that plant-plant interaction occurs among root systems via the soil as a medium.

  • In some Epiphytes – plants living above the surface on other plants, aerial roots serve for reaching to water sources or reaching the surface, and then functioning as regular
    surface roots.

  • • Structural roots: large roots that have undergone considerable secondary thickening and provide mechanical support to woody plants and trees.

  • The majority of roots on most plants are however found relatively close to the surface where nutrient availability and aeration are more favourable for growth.

  • [20] The correct environment of air, mineral nutrients and water directs plant roots to grow in any direction to meet the plant’s needs.

  • Early research in the 1930s found that light decreased the effectiveness of Indole-3-acetic acid on adventitious root initiation.

  • [23] Research indicates that plant roots growing in search of productive nutrition can sense and avoid soil compaction through diffusion of the gas ethylene.

  • Studies of the pea in the 1950s shows that lateral root formation was inhibited by light, and in the early 1960s researchers found that light could induce positive gravitropic
    responses in some situations.

  • [45] Economic importance The term root crops refers to any edible underground plant structure, but many root crops are actually stems, such as potato tubers.

  • When dissected, the arrangement of the cells in a root is root hair, epidermis, epiblem, cortex, endodermis, pericycle and, lastly, the vascular tissue in the centre of a
    root to transport the water absorbed by the root to other places of the plant.

  • The main hormones (intrinsic stimuli) and respective pathways responsible for root architecture development include: Growth Early root growth is one of the functions of the
    apical meristem located near the tip of the root.

  • • Surface roots: roots that proliferate close below the soil surface, exploiting water and easily available nutrients.

  • [26] Types A true root system consists of a primary root and secondary roots (or lateral roots).

  • • Proteoid roots or cluster roots: dense clusters of rootlets of limited growth that develop under low phosphate or low iron conditions in Proteaceae and some plants from
    the following families Betulaceae, Casuarinaceae, Elaeagnaceae, Moraceae, Fabaceae and Myricaceae.

  • • Coralloid roots: similar to root nodules, these provide nitrogen to the plant.

  • The latter become the primary tissues of the root, first undergoing elongation, a process that pushes the root tip forward in the growing medium.

  • In the roots of the plant HY5 functions to inhibit an auxin response factor known as ARF19, a response factor responsible for the translation of PIN3 and LAX3, two well known
    auxin transporting proteins.

  • The first root originating from the seed usually has a wider diameter than root branches, so smaller root diameters are expected if temperatures increase root initiation.

  • From here, they altered the different wavelengths of light the shoot and root of the plants were receiving and recorded the lateral root density, amount of lateral roots,
    and the general architecture of the lateral roots.

  • Function The major functions of roots are absorption of water, plant nutrition and anchoring of the plant body to the ground.

  • Depths The distribution of vascular plant roots within soil depends on plant form, the spatial and temporal availability of water and nutrients, and the physical properties
    of the soil.

  • [4] Scientists have observed significant diversity of the microbial cover of roots at around 10 percent of three week old root segments covered.

  • were able to theorize that shoot located phytochromes alter auxin levels in roots, controlling lateral root development and overall root architecture.

  • Roots often function in storage of food and nutrients.

  • • 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.

  • The migration of bacteria along the root varies with natural soil conditions.

  • Gravitropism directs roots to grow downward at germination, the growth mechanism of plants that also causes the shoot to grow upward.

  • Researchers have tested whether plants growing in ambient conditions would change their behavior if a nearby plant was exposed to drought conditions.

  • Secondary growth encompasses all growth in diameter, a major component of woody plant tissues and many nonwoody plants.

  • • Propagative roots: roots that form adventitious buds that develop into aboveground shoots, termed suckers, which form new plants, as in Canada thistle, cherry and many others.

  • [11] Extrinsic factors affecting root architecture include gravity, light exposure, water and oxygen, as well as the availability or lack of nitrogen, phosphorus, sulphur,
    aluminium and sodium chloride.

  • [14] It is also postulated that suberin could be a component of the apoplastic barrier (present at the outer cell layers of roots) which prevents toxic compounds from entering
    the root and reduces radial oxygen loss (ROL) from the aerenchyma during waterlogging.

  • were able to develop a mechanism for how root detection of Red to Far-red light ratios alter lateral root development.

  • Calcium deficiency did, on the other hand, lead to a marked decline of polyunsaturated compounds that would be expected to have negative impacts for integrity of the plant
    membrane, that could effect some properties like its permeability, and is needed for the ion uptake activity of the root membranes.

  • The effects of light on root elongation has been studied for monocotyledonous and dicotyledonous plants, with the majority of studies finding that light inhibited root elongation,
    whether pulsed or continuous.

  • Perennial grasses that grow wild in rangelands contribute organic matter to the soil when their old roots decay after attacks by beneficial fungi, protozoa, bacteria, insects
    and worms release nutrients.


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