Nodule bacteria are microorganisms that belong to the genus Rhizobium (literally from the Greek. - "Living on the roots").They are introduced to the root system of the plant and live there.However, they are not parasites, t. To. Not only bacteria, but also the flora benefited.Such mutually beneficial existence of organisms is called symbiosis.In this case, further plants are produced by atmospheric nitrogen which "catch" the microorganisms and the bacteria themselves - carbohydrates and minerals.Some people believe that these prokaryotes settle in the roots only representatives of the legume family, but it is not.There are other plants whose roots provide habitat nodule prokaryotes - such as alder, reed forest and so on. D.
to sort organisms Rhizobium characteristic polymorphism, t. E forms of bacteria are very diverse.These microorganisms can be mobile and immobile, take the form of coccus or bacillus, filamentous oval.In most young prokaryotes are rod-shaped, which with increasing age and varies due to the accumulation of nutrients and immobilization.In its life cycle organism goes through several stages, which can be judged by his appearance.Initially, this rod shape, and then the so-called "belted sticks" (having bands with fat inclusions) and finally bakteriod - large stationary cage of irregular shape.
Nodule bacteria are specific, ie. E. They are able to settle only in a specific group or type of plant.This property microorganisms genetically formed.Also important is the effectiveness - the ability to accumulate atmospheric nitrogen in sufficient quantity for its host plant.This property is not constant and may vary due to environmental conditions.
about how nodule bacteria get into the root, there is no consensus, however, there are a number of hypotheses about the mechanism of their penetration.For example, some scientists believe that the root of prokaryotes introduced by damaging the tissue, while others speak of penetration through the root hairs.There is also an auxin hypothesis - the assumption of satellite cells, which help the bacteria to be introduced into the cells of the root.
very same introduction takes place in two phases: first - infection of root hairs, then - the formation of nodules.The duration of the phases varies and depends on the type of plant.
Meaning of bacteria that can fix nitrogen, great for agriculture, t. To. These organisms can increase productivity.Of these microorganisms bacterial fertilizer is prepared, which is used for the treatment seeds from leguminous that promotes faster infected roots.Various family papilionaceous landing even in poor soils do not require additional nitrogen fertilizer.So, 1 hectare of legumes "in" with rhizobia for the year translates into a bound state of 100-400 kg of nitrogen.
Thus, nodule bacteria - symbiotic organisms, which are very important not only in the life of the plant, but the nitrogen cycle in nature.
