The plant root system influences plant growth and development due to its phenotypic, physiological, metabolomic, and microbiomic traits. Broadly speaking, it is characterized by primary (stem-attached large), secondary (primary-attached medium), and fine (secondary-attached hair-like) roots. The role of root branching order and categories (fine, medium, and large) in influencing microbial communities in the rhizosphere and root environments is not clear.
Salinity stress adversely affects root nodulation symbiotic relationships, and ultimately the nitrogen fixation capacity and the growth and yield of leguminous plants. Improving growth and biological nitrogen fixation of leguminous plants grown on salt–affected soils are considered to be a striking challenge.