Scientists MV Lomonosov from Moscow State University together with colleagues from the Main Botanical Garden. NV Tsitsina RAS found that special bacteria living on the roots of leafless orchids help plants obtain nutrients and survive conditions of moisture deficiency. The results were published in the journal microorganisms.
Orchids are one of the most numerous flowering families. They are mainly found in the tropics, and about 70% live on the trunks and crowns of trees – such plants are called epiphytic. Unlike soil plants, they are forced to live with a lack of moisture and excessive ultraviolet radiation.
A frugal metabolism has resulted in its leaves turning into small scales. The usual functions of the leaves were taken over by aerial roots covered with a special moisture-absorbing fabric – velamen, protected from ultraviolet radiation and mechanical damage.
Velamen is home to many fungi and bacteria. Earlier, microbiologists at Moscow State University managed to find out that among its inhabitants, aerial roots have bacteria that help green-leaved orchids absorb nitrogen. In addition, these microbes secrete auxins, which are plant hormones that affect the life processes of orchids.
In a new study, biologists studied leafless orchids. Chiloschista parishii Seidenf. And Microcoelia moreauae L. Jonss. They took samples from the roots of greenhouse plants and studied their composition and function using DNA sequencing.
As with the leafy orchids, cyanobacteria predominated in the roots in the leafless species studied, but their species composition turned out to be much broader. They also form much larger biofilms than leafy orchids. In addition, the bacterial composition varied depending on the root development stage.
Overall, the results of the study showed a close relationship between leafless orchids and their companion bacteria. Cyanobacteria colonize the aerial roots of plants, fertilizing the plants with nitrogen-containing compounds.
Another example of this type of cooperation is the water fern. Azola and cyanobacteria living in the hollows of its leaves anabaena. This fern is used as a bio-fertilizer in rice fields, where it enriches it with additional nitrogen.