What is the root? It is a very important plant organ that ensures its growth and vital activity. Scientists associate the appearance of this organ with the stage of development of the flora of the earth's surface.
The root is the underground part of the plant, which has apical growth and has a radial structure.
The main functions of the root are:
- anchor - that is, the retention of the plant in the soil;
- and absorbing - receiving from the earth water and minerals transported through xylem (water conducting tissue) to all aboveground plant parts for the production of photosynthesis.
In addition, organic substances synthesized in the aerial part of the plant, as well as in the root itself, hormones, amino acids, alkaloids, etc., accumulate in it and are a supply of nutrients. The root is also an organ of vegetative propagation of the plant.
Along with the definition of what the root is, the concept of the root system always appears, which is formed by all the roots of the plant in the aggregate. Distinguish between the main, subordinate and lateral roots.
The main (or primary) root gets its development even in the germinal root. In flowering and gymnosperms, the main root is the main, has unlimited growth and positive geotropism (that is, it gives the right direction for plant growth).
The adnexal roots are secondary and grow from stems, old roots or leaves.
Lateral roots grow from the main and subordinate.
Root systems are rod or fibrous in type. With a rooted root system, the primary root is very pronounced. This system is mainly possessed by dicotyledonous plants (for example, carrots, dandelion, watermelon, sunflower). With a fibrous root system, the growth of the main root is not very pronounced, it does not stand out among the subordinate roots (for example, valerian root, plantain, rye). Such a root system is typical mainly for monocotyledonous plants.
The internal structure of the roots
What is the root, in terms of its internal structure? In its center is a conductive root system, consisting of sieve tubes and vessels. Vessels provide transportation of water, along with useful substances dissolved in it, to the aerial parts of the plant from root hairs. Sieve tubes, in contrast, transport organic solutions from terrestrial organs to root cells. Cells of the educational tissue of the root (cambium) are continuously divided and ensure that the roots grow in thickness.
What is the root, and all its main zones are clearly visible in a longitudinal section.
The root cap is formed by the integumentary tissue and covers the top of the root, protecting it like a cap from various injuries. Its other function is to promote the advancement of the root in the earth.
The division zone is located immediately under the root cover and consists of small cells of the educational tissue, which by their constant division provide root growth.
The extension zone is formed by very young, only growing cells, elongating in the longitudinal direction and thereby realizing root growth in length.
If you carefully dig up the plant, you can see how the roots braid the soil particles, this part is called the absorption zone. It is covered with root hairs, the function of which is the absorption of water with nutrients. Hair has a slug surface.
Above the suction zone is the conduction zone formed by the conductive tissue and making up most of the root length. Through the vessels of the root, water and mineral substances, which are directly dissolved in it, move up the stem.
In some plants, the roots can be modified due to the appearance of conditions unfavorable for plant growth and providing adaptation to them.