The root is an important organ of the plant. It performs several vital functions: it provides soil nutrition, keeps the plant in the ground, participates in vegetative propagation, and in some cases creates a supply of nutrients. In the article, special attention will be paid to adventitious roots and their functions will be considered.
Historical development of the root
According to phylogenetics, which identifies evolutionary changes among different types of life on Earth, the root of the plant appeared later than the stem and leaf. This happened during the transition of plants to existence on earth. To fix on solid ground, they needed special organs, the beginning of which was underground branches similar to roots, which later turned into roots. They do not contain leaves and buds and grow in length by dividing apical cells.
Lateral and adventitious roots emerge from the tissues contained within the roots and stems, the growing point of which is covered to prevent damageroot cap. The root system does not stop forming throughout the life and development of the plant.
Basic root functions
The root is called the axial, mostly underground part of the higher vascular plant, which has unlimited growth in length down to the center of the globe. The main functions of the roots are as follows:
- absorb minerals from the soil along with water;
- store nutrients;
- fix and fix the plant in the soil;
- interact with organisms in the ground: bacteria and fungi;
- synthesize hormones, enzymes and amino acids;
- promote reproduction;
- ensure breathing.
Types of roots
The root system of a plant consists of the totality of all roots. All of them differ in importance and origin. There are three types of roots:
- Main - its development comes from the germinal root of the seed. It grows indefinitely and is always directed downward towards the center of the globe, and it has an active apical tissue that retains the ability to divide and form new cells for a long time.
- Adnexal - in appearance they are similar to the side ones and perform the same functions. Adventitious roots are formed from leaves, stems and old roots. Thanks to their development, the plant is able to reproduce vegetatively.
- Lateral - develop on other roots of any origin, are formations of the second and next orders of branching. Their occurrence occurs with the division of a special meristem(educational tissue capable of dividing), located on the peripheral part of the central cylinder of the root.
Each of the roots: the main lateral and adnexal are capable of branching. And this significantly increases the root system, which improves plant nutrition and strengthens it in the soil.
Classification of root systems by origin and form
The totality of all the roots of a plant: the main, lateral and adnexal forms the root system. There are three types of them:
- Rod - the plant is dominated by the development of the main root. It is long and much thicker than the side ones. The rod system is characteristic of many dicots: clover, beans, dandelion.
- Fibrous - adventitious roots predominate, as well as lateral ones. The main one develops slowly and stops growing early. Such a root system is inherent in rye, onions, corn.
- Mixed - with a large main root, can be taproot, fibrous - with the same size of all roots.
Often, roots perform different functions within the same system:
- skeletal, support the plant;
- growth - there is increased growth and slight branching;
- sucking - thin, branching profusely.
Classification of roots by origin
By origin, the roots are divided into several types. The main root is formed from the root of the embryo and includes the main root and lateral roots of several orders. Such a system is seen inmost trees and shrubs, as well as herbaceous plants, the embryo of which contains only one cotyledon and a number of dicotyledonous perennials.
Adventitious root - it is formed on leaves, stems, old roots, and sometimes on flowers. Such a source of roots is considered primitive because it is characteristic of spore plants. Mixed - occurs in plants with one and two germinal lobes. First, the main root begins to grow and develop from the seed, but by the autumn of the first year of life, its growth stops, and the main root system makes up a small part of the entire root system. In the second and subsequent years, adventitious roots form at internodes, nodes, above and below nodes. After about three years, the main root dies off and the plant has only roots on stems and leaves.
Formation of the root system
When the tip of the root is damaged, its growth in length stops. At the same time, many lateral roots begin to form, located shallowly, in the fertile soil layer. Using this property, for example, when transplanting cabbage, they pinch off (the technique is called pinching) the tip of the main root and transplant the plant with a stick (spikes) - they dive the plant.
It, with a well-developed root system, receives more nutrients and water, so it grows and develops faster. You can also increase the number of roots in the nutrient layer of the earth with the help of hilling. To do this, the near-ground trunk of the plant is covered with soil, thenadventitious roots grow from it, extracting additional nutrition. Hilling is usually carried out after rain or heavy watering at a plant height of at least 20 cm, and again after two weeks. During this procedure, the soil is loosened, which ensures good root growth. In summer cottages, for example, hoes are used for hilling potatoes, and in the fields - different types of hillers.
Root system of cereal crops
Among flowering plants, cereals occupy a special position. They are divided into cultivated and meadow. All have a fibrous root system. It is formed with an underdeveloped main and its early replacement with adventitious roots of the plant. They are laid down in the stalk of the embryo and begin development when the seed germinates along with the main root. And after a few days, secondary roots begin to appear, which are formed from underground stem nodes. And in crops such as sorghum and corn, root development occurs from above-ground nodes close to the topsoil. They help the plant to remain stable during strong winds. The primary roots of cereals penetrate to great depths, but their bulk is located in the upper, fertile layer.
Dependence of roots on natural conditions
The main root of plants, containing an embryo with two cotyledons, is usually preserved for the entire period of their existence. The embryonic root of monocots, on the contrary, quickly dies off, the development of the main root does not occur, and branching of roots of several orders begins to occur from the base of the shoot. Adventitious roots develop on leaves and stems. This feature of plants is used for propagation by both leaf and stem cuttings. In the first way, begonia, violet are bred, in the second - blackcurrant, willow, poplar. Underground cuttings (rhizomes) are often used to propagate medicinal plants - kupena, lily of the valley.
Higher spore plants - fern and horsetail - do not have a main root at all, their roots branch only from the rhizome. In some dicotyledons (nettles, goutweeds), the main root often dies off, but others appear, extending from the rhizomes. The roots of the rod system penetrate deepest into the ground. But the fibrous roots of plants prevent soil erosion and are involved in the creation of a sod cover. The root system of plants in different natural areas and on different soils is not the same. It is known that the roots can go up to 40 or more meters deep in deserts, with deep groundwater. But ephemera, which have surface roots, due to lack of moisture, have adapted to go through all phases of the growing season in a short period of time. The roots of the saxaul shrub growing in the desert are fed with water in different periods of the year from unequal earth layers. The development of the root system in each plant species depends on natural conditions, but at the same time it is the same for one variety.
Conclusion
Without roots, the life of higher vascular plants is impossible. To obtain a complete diet, including minerals and water, a developedroot system, consisting of lateral, main and adventitious roots.
In addition, the roots keep the plant in the soil, protecting it from heavy rains and strong winds, and also promote reproduction. Yes, and they have a beneficial effect on the soil, strengthening its upper layer in loose, sandy, making clay and rocky soils more loose.
