The root is the underground axial element of plants, which is their most important part, their main vegetative organ. Thanks to the root, the plant is fixed in the soil and held there throughout the life cycle, and is also provided with water, mineral and nutrients contained in it. There are different types and types of roots. Each of them has its own distinctive characteristics. In this article we will consider the existing types of roots, types of root systems. Also get acquainted with their characteristic features.
What types of roots are there?
The standard root is characterized by a filiform or narrow cylindrical shape. Many plants, in addition to the main (main) root, also develop other types of roots - lateral and subordinate. Let us consider in more detail what they are.
Main root
This plant organ develops from the germinal root of the seed. The main root is always one (other types of plant roots are usually present in the plural). It is preserved in the plant throughout the entire life cycle.
The root is characterized by positive geotropism, that is, due to gravity, it deepens vertically down into the substrate.
Adnexal roots
Adjunctive species of plant roots, which are formed on their other organs. These organs can be stems, leaves, shoots, etc. For example, cereals have the so-called primary subordinate roots, which are still in the stalk of the seed germ. They develop in the process of seed germination almost simultaneously with the main root.
There are also leaf subordinate types of roots (formed as a result of rooting of leaves), stem or nodular (formed from rhizomes, aboveground or underground stem nodes), etc. Powerful roots are formed on the lower nodes, which are called aerial (or supporting).
The appearance of subordinate roots determines the ability of a plant to vegetatively propagate.
Side roots
Lateral roots are roots that arise as a lateral branch. They can form both on the main and on the subordinate roots. In addition, they can branch off from the lateral, as a result of which lateral roots of higher orders (first, second and third) are formed.
Large lateral organs are characterized by transverse geotropism, that is, their growth occurs in an almost horizontal position or at an angle to the soil surface.
What is called the root system?
The root system refers to all types and types of roots that are present in one plant (that is, their combination). Depending on the ratio of growth of the main, lateral and adnexal roots, its type and character are determined.
Types of Root Systems
Distinguish rod and fibrous root systems.
If the main root is very well developed and visible among the roots of another species, this means that the plant has a core system. It is inherent mainly in dicotyledonous plants.
The root system of this type is characterized by deep germination in the soil. So, for example, the roots of some herbs can penetrate to a depth of 10-12 meters (sow thistle, sowing alfalfa). The depth of penetration of tree roots in some cases can reach 20 m.
If the subordinate roots, which develop in large numbers, are more pronounced, and the main one is characterized by slow growth, then a root system is formed, which is called fibrous.
Such a system is characterized, as a rule, by monocotyledonous plants and some of the herbaceous plants . Despite the fact that the roots of the fibrous system do not penetrate as deep as in the core, they better braid the soil particles adjacent to them. Many loose and rhizome cereal grasses, forming an abundant amount of fibrous thin roots, are widely used to fix gullies, soils on slopes, etc. The best grass-closing plants include creeping wheatgrass, boneless fire, fescue, meadow bluegrass , etc.
Mutated roots
In addition to the typical ones described above, there are other types of roots and root systems. They are called mutated.
Reserve roots
Root crops and root tubers belong to storing.
The root crop is a thickening of the main root due to the deposition of nutrients in it. Also, the lower part of the stem is involved in the formation of the root crop. It consists mainly of storage core tissue. Examples of root vegetables are parsley, radish, carrots, beets, etc.
If the thickened storage roots are the lateral and subordinate roots, then they are called root tubers (cones). They are developed in potatoes, sweet potatoes, dahlias, etc.
Aerial roots
These are lateral roots growing in the aerial part. Present in a number of tropical plants. Water and oxygen are absorbed from the air. Available in tropical plants growing in conditions of lack of minerals.
Respiratory roots
This is a type of lateral roots that grow upward, rising above the surface of the substrate, water. Such types of roots are formed in plants growing on too moist soils in the conditions of swamps. With the help of such roots, the vegetation receives the missing oxygen from the air.
Supporting (plank) roots
These types of tree roots are characteristic of large species (beech, elm, poplar, tropical, etc.). They are triangular vertical outgrowths formed by lateral roots and passing at or above the surface of the soil. They are also called plank because they resemble boards that are leaning against a tree.
Suction Roots (Haustoria)
Observed in parasitic plants that do not know how to synthesize. The nutrients necessary for normal functioning, they get by growing into the stem or root of other plants. At the same time, they are introduced into the phloem and xylem. Examples of parasitic plants are dodder, broomrape, and rafflesia.
Gaustoria of semi-parasite plants with photosynthetic abilities grow only in xylem, taking only mineral substances from the host plant (ivan da marja, mistletoe, etc.)
Hook Roots
This is a type of additional subordinate roots developing on the stem of climbing plants. With their help, plants have the ability to attach to a specific support and rise (trail) up. Such roots are, for example, in ficus tenacious, ivy, etc.
Retractable (contractile) roots
Characteristic for plants whose root is sharply reduced in the longitudinal direction at the base. An example is plants having bulbs. Retractable roots provide some bulbs and roots to the soil. In addition, their presence determines the tight fit of the sockets (for example, a dandelion) to the ground, as well as the underground position of the vertical rhizome and root neck.
Mycorrhiza (fungus root)
Mycorrhiza is called symbiosis (mutually beneficial cohabitation) of the roots of higher plants with fungal hyphae that braid them, performing the functions of root hairs. Mushrooms provide plants with water and nutrients dissolved in it. Plants, in turn, give the mushrooms the organic substances necessary for their vital functions.
Mycorrhiza is inherent in the roots of many higher plants, especially woody ones.
Bacterial nodules
These are modified lateral roots that are adapted for symbiotic cohabitation with nitrogen-fixing bacteria. The formation of nodules occurs due to the penetration of nitrogen-fixing bacteria into young roots. Such mutually beneficial cohabitation allows plants to receive nitrogen, which bacteria convert from the air into an accessible form for them. Bacteria are given a special habitat where they can function without competing with other types of bacteria. In addition, they use substances present in the roots of vegetation.
Bacterial nodules are characteristic for plants of the legume family, which are widely used as ameliorants in crop rotation in order to enrich the soil with nitrogen. The best nitrogen-fixing plants are rooted bean herbs, such as blue and yellow alfalfa, pink, red and white clover, clover, sainfoin, horned lamb, etc.
In addition to the above metamorphoses, there are other types of roots, such as props (help strengthen the stem), stilted roots (help plants not to drown in liquid mud) and root offspring (have additional buds and provide vegetative propagation).