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Microbiological activity is very important in agricultural production systems. Most microorganisms maintain beneficial relationships or associations with plant species and are stimulated through substances secreted by plants, in what is known as rhizospheric effect. The associations between plants and microorganisms can occur in the phyllosphere, which is the leaf surface of the plant, or in the rhizosphere, which is the region of the soil in close contact with the roots.
In this Green Ecologist article we will focus on the latter region and talk about what is the rhizosphere, what is it for, its composition and its importance. If you continue reading, you will discover not only some of the characteristics of the rhizosphere that define its importance, but also what keys allow it to improve and maintain its functionality.
What is the rhizosphere and what is it for?
The rhizosphere, considered to be the largest terrestrial ecosystem, is the part of the soil near the roots of the plant, which extends specifically between 1 and 3 mm from the surface of the roots to the interior of the soil.
In this edaphic region plant roots interact with the soil and its microorganisms, which consequently provides benefits for plants, improves soil fertility and favors the degradation of toxic chemical substances. It is an association known as rhizocenosis, which allows either to obtain food, as in mycorrhizae, or to fix nitrogen, in which bacteria, called rhizobacteria, generally participate, such as Azospirillum, Azotobacter Y Bacillus (plant growth promoters) in grass roots and Beijerinckia in sugar cane roots.
The scientific community distinguishes 3 different parts that make up the rhizosphere:
- The endorizosphere or internal rhizosphere It comprises the root cortex (tissue between the endodermis and the epidermis) invaded by microorganisms.
- The rhizoplane or rhizoplane It is formed by the surface of the root and the microorganisms that are in it.
- The ectorizosphere, exorhizosphere, rhizospheric soil, or outer rhizosphere It is the part of the soil that is in close contact with the root surface of the plants.
Composition of the rhizosphere
In general terms, we can say that the rhizosphere composition is: soil, water, radical depositions (exudates and mucilage) and microbiota (bacteria, fungi, algae).
On the one hand, the soil acts as a physical support and provides food for the plants. Their physicochemical properties determine the presence and distribution of microorganisms, while their conservation depends on them. We can stand out the pH as an abiotic factor that conditions and characterizes the frhizosphere union, since changes in its value can lead to the inactivation of the enzymes present in the microorganisms and disturb the fixation of nutritive minerals. In this region the pH values are lower or more acidic compared to the rest of the soil, which is due to cation exchange and the production of organic acids.
On the other hand, Water which is an essential resource for life, plays a very important role in the rhizospheric interactions. Its availability is directly related to the porosity of the soil and, to a certain extent, its potential is controlled by the microbiota. In fact, microorganisms improve aeration soil and infiltration capacity, thus favoring the maintenance of the water film in the rhizosphere.
Regarding radical stools, plants release photosynthetic products (sugars, amino acids, vitamins, organic acids, hormones) through their radical exudates which, if they are of low molecular weight, can favor the diversity and microbe growth of the rhizosphere. These organic compounds attract microorganisms to the surface of the roots, constituting a very important source of food and energy for them. One of these exudates is mucigel, which is a gelatinous material that covers the surface of plant roots, made up of: plant mucilage, bacterial cells, polysaccharides, mineral colloids and soil organic matter.
Finally, the microorganisms that inhabit the rhizosphere (bacteria, fungi, protozoa and nematodes), mostly report benefits. The rhizosphere bacteria or rhizobacteria They are responsible for decomposing radical exudations and plant residues. The fungi also stand out, which establish a symbiotic relationship with the roots, known as mycorrhizaSince, like bacteria, they are capable of degrading or mineralizing toxic and harmful substances in a process called detoxification. In this other article we will tell you more about what mycorrhizae are and their types.
Importance of the rhizosphere
The importance of the rhizosphere it resides in the interactions that take place between plants and the soil microbiota. Why? Well, because in line with what was stated in previous sections:
- Through the rhizosphere, plants take in nutrients. The same happens with water and carbon that bacteria, fungi, insects, worms and protozoa need to survive.
- The microflora of the rhizosphere protects the root against pathogens, against root diseases and produces substances that stimulate plant growth, such as indoleacetic acid, ghibellins and cytokinins.
- Biological Nitrogen Fixation (BNF) occurs, that is, microorganisms provide plants with assimilable nitrogen compounds (ammonium and nitrate), which they manufacture from soil atmospheric nitrogen (N2).
How to improve the rhizosphere
It is well known that nitrogen is a limiting factor for plants because, despite its abundance in the atmosphere (it represents approximately 80% of its composition), they cannot take advantage of it in the molecular form in which it is found (N2). This situation has led to the massive use of chemical fertilizers to increase crop productivity. Consequently, important pollution processes have been unleashed in the natural environment that decrease soil fertility and the quality of soil and water resources. One way to avoid this is to make visible the fixing capacity possessed by the microorganisms of the rhizosphere, which can satisfy the plant nitrogen demand, by using biofertilizers.
If you want to read more articles similar to Rhizosphere: what is it, what is it for, composition and importance, we recommend that you enter our Ecosystems category.
Bibliography- Reyes Jaramillo, I. (June 23, 2011). Dept. of Biology, Division of CBS. UAM-Iztapalapa. The arbuscular mycorrhiza (AM) center of the rhizosphere: dynamic microbiological community of the soil: http://www2.izt.uam.mx/newpage/contactos/revista/81/pdfs/micorriza.pdf
