Clearly that plants coexisting with fungi for nitrogen fixation had relieved the relationship many times in the past

"Nitrogen" of the constituent elements of amino acids is an indispensable substance when living beings live. However, since plants can not directly take in nitrogen from the air, special plants that can immobilize nitrogen in the air may be used.Nitrogen fixingThe genetic information of the plants coexisting with the fungus was examined, and it turned out that there is a past that has resolved the symbiotic relationship many times during the process of evolution.

Phylogenomics reveals multiple losses of nitrogen-fixing root nodule symbiosis | Science
http://science.sciencemag.org/content/early/2018/05/23/science.aat1743

Plants repeatedly got rid of their ability to obtain their own nitrogen | Ars Technica
https://arstechnica.com/science/2018/05/plants-repeatedly-got-rid-of-their-ability-to-obtain-their-own-nitrogen/

Plant symbioses - fragile partnerships - ScienceDaily
https://www.sciencedaily.com/releases/2018/05/180524141556.htm

Nitrogen is essential for plants as well as other organisms to make molecules necessary for ecology such as amino acids. It is nitrogen that accounts for about 80% of the air, but it is inactive and can not be taken directly into the body and it is necessary to "immobilize" it. Since plants can not immobilize nitrogen in the air, basically they will incorporate nitrogen from soil into the body in a form linked to hydrogen such as fertilizer.

In contrast, some fungi can immobilize nitrogen in the air, there are several known plants such as legumes that incorporate this bacterium into the body and coexist. This fungus is "RhizobiumIt is called "nodule" as its name, and it lives with plants in the cob of the root of the plant called "nodule". This is a relationship that is held together, "Rhizobium provides ammonia with nitrogen immobilized for plants, plants produce energy sources through photosynthesis and provide them for life support" It is.


An international research group centered on Ludwig Maximilians University Munich analyzed the genome of 37 different plants, including plants coexisting with Rhizobium. Researchers focused on genes called "Nodule Inception (NIN)", which is an essential condition for coexistence with Rhizobium, and found that among functions of several different strains, functions are activated and invalidated I understood that I have repeated it. Amazingly, varieties that have coexisted with fungi in the past have also been found in strawberries, apples, and blackberries.

It is thought that plants coexisting with Rhizobium are symbiotic survivors who stably provide nitrogen from fungi even in an environment where it is difficult to take in nitrogen from the soil, but depending on the environmental change, About Maximilian Griesmann's "Cost of harmonious coexistence with fungus" for reason why stopping symbiosis of frequent occurrence is cited. According to researchers, the plant coexisting with Rhizobium must provide not only the life activity of the fungus, but also the energy consumed for nitrogen fixation, and this total energy is very high. If the conditions of use such as water and phosphorus change, the coexistence cost with fungi will not be won favorably and the plant may choose to resolve the coexistence relation.


Although chemical fertilizers are used to efficiently supply nitrogen to agricultural crops, the disadvantage that use of chemical fertilizer increases the emission of greenhouse gases is pointed out, including the manufacturing process of chemical fertilizers. In order to solve this problem, research is being carried out to incorporate genes that can be fixed in nitrogen in living organisms, but researchers who carried out this research have confirmed that plants, by their own choice, We should note that there is a past where we have removed our abilities.