Root is the underground axial element of plants, which is the most important part of them, their main vegetative organ. Thanks to the root, the plant is fixed in the soil and held there throughout its life cycle, and is also provided with water, minerals and nutrients contained in it. There are different kinds 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. We will also get acquainted with their characteristic features.
What are the types of roots?
Standard root is characterized by filiform or narrow cylindrical shape. In many plants, in addition to the main (main) root, other types of roots are also developed - lateral and adventitious. Let's take a closer look at what they are.
Main root
This plant organ develops from the germinal root of the seed. There is always one main root (other types of plant roots are usually plural). It is stored in the plant throughout the entire life cycle.
The root is characterized by positive geotropism, that is, due to gravity, it deepens into the substrate verticallydown.
Adventitious roots
Adventitious are the types of plant roots that form on their other organs. These organs can be stems, leaves, shoots, etc. For example, cereals have so-called primary adventitious roots, which are laid down 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 adventitious types of roots (formed as a result of rooting of leaves), stem or nodal (formed from rhizomes, above-ground or underground stem nodes), etc. Powerful roots are formed on the lower nodes, which are called aerial (or supporting).
The appearance of adventitious roots determines the plant's ability to vegetative reproduction.
Lateral roots
Lateral roots are called roots that appear as a lateral branch. They can form both on the main and adventitious roots. In addition, they can branch off from lateral roots, 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 a root system?
Root system refers to all kinds and types of roots that one plant has (that is, their totality). Depending on the ratio of growth of the main, lateral and adventitious roots, its type and character is determined.
Types of root systems
Distinguish between taproot and fibrous root systems.
If the main root is very well developed and noticeable among the roots of another species, this means that the plant has a rod system. It is present mainly in dicotyledonous plants.
The root system of this type is characterized by deep germination into the soil. So, for example, the roots of some grasses can penetrate to a depth of 10-12 meters (thistle, alfalfa). The depth of penetration of tree roots in some cases can reach 20 m.
If the adventitious roots are more pronounced, developing in large numbers, and the main one is characterized by slow growth, then a root system is formed, which is called fibrous.
As a rule, monocot plants and some of herbaceous plants are characterized by such a system. Despite the fact that the roots of the fibrous system do not penetrate as deeply as those of the rod system, they better braid the soil particles adjacent to them. Many loose shrub and rhizomatous grasses, which form an abundant amount of fibrous thin roots, are widely used to fix ravines, soils on slopes, etc. The best herbs-reinforcers include creeping couch grass, awnless brome, fescue, meadow grass, etc.
Modified roots
Besides the typical ones described above, there are other types of roots and root systems. They are called modified.
Storage roots
Reserves include root crops and root tubers.
A 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. Consists mostly of storage base tissue. Examples of root crops are parsley, radishes, carrots, beets, etc.
If the thickened storage roots are lateral and adventitious 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. Found in a number of tropical plants. Water and oxygen are absorbed from the air. Found in tropical plants growing under conditions of mineral deficiency.
Respiratory roots
This is a kind 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 swamp conditions. With the help of such roots, vegetation receives the missing oxygen from the air.
Support (board-shaped) 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 near or above the soil surface. They are also called board-like because they resemble boards that are leaning against a tree.
Sucker roots (haustoria)
Observed in parasitic plants that cannotphotosynthesize. They receive the nutrients necessary for normal functioning by growing into the stem or root of other plants. At the same time, they are introduced both into the phloem and into the xylem. Examples of parasitic plants are dodder, broomrape, rafflesia.
Haustoria of semi-parasitic plants with photosynthetic abilities grow only into the xylem, taking only mineral substances from the host plant (Ivan da Marya, mistletoe, etc.)
Hook Roots
This is a kind of additional adventitious roots developing on the stem of climbing plants. With their help, plants have the ability to attach to a certain support and climb (weave) up. Such roots are available, for example, in tenacious ficus, ivy, etc.
Retractable (contractile) roots
Characteristic for plants whose root is sharply reduced in the longitudinal direction at the base. An example would be plants that have bulbs. Retractable roots provide bulbs and root crops with some recess in the soil. In addition, their presence is determined by the tight fit of rosettes (for example, at a dandelion) to the ground, as well as the underground position of the vertical rhizome and root collar.
Mycorrhiza (fungus root)
Mycorrhiza is a symbiosis (mutually beneficial cohabitation) of the roots of higher plants with fungal hyphae, which braid them, acting as root hairs. Fungi provide plants with water and nutrients dissolved in it. Plants, in turn, provide fungi with the nutrients they need to survive.organic matter.
Mycorrhiza is inherent in the roots of many higher plants, especially woody ones.
Bacterial nodules
These are modified lateral roots that are adapted to 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 transfer from the air into a form accessible to them. Bacteria, on the other hand, 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 typical for plants of the legume family, which are widely used as ameliorants in crop rotations to enrich soils with nitrogen. Taproot legumes such as blue and yellow alfalfa, pink clover, red and white clover, sweet clover, sainfoin, horned bird's foot, etc. are considered the best nitrogen-fixing plants.
In addition to the above metamorphoses, there are other types of roots, such as support roots (help strengthen the stem), stilted roots (help plants not to sink in liquid mud) and root suckers (have adventitious buds and provide vegetative reproduction).
