The rhizosphere as a multicompartment open system influences plant performance, health and productivity. Multiple gradients of matter, and associated herewith, of populations, are found in the rhizosphere.

Whereas soil and climate characteristics determine the species distribution in a given space, plants and rhizosphere organisms influence and benefit from each other.

Examples are:

• mycorrhiza i.e. symbiosis between plant roots and fungi (with special adaptations, e.g. VA-mycorrhiza, ectomycorrhiza, orchid mycorrhiza and mycorrhiza of the Ericaceae). About 90% of all land plants form the mycorrhizal relationships with fungi. It is estimated that mycorrhizal fungal filaments explore hundreds to thousands more soil volume compared to roots alone.The benefits to the plant include an improved nutrient and water uptake, associated with improved root growth. This leads to improved plant growth and yield, and reduced drought stress.
• plant growth promoting bacteria (PGPR). Plants have latent defense mechanisms against pathogens which can be systemically activated by exposure of plants to stress or infection. This phenomenon, called systemic acquired resistance or induced systemic resistance, operates through the activation of defense genes and the accumulation of defense compounds at a site distant from the point of pathogen attack. PGPR bacteria induce this SAR / ISR genes without being harmful to the plant.
• rhizobia, collectively for Gram-negative, nitrogen-fixing bacteria forming nodules on host plants. They live in symbiotic relationship with legume plants, which can't live without these bacteria's essential nitrogen-fixing processes. The rhizobia bacteriods obtain carbon and energy from the plant in the form of dicarboxylic acids.
• allelopathy, i.e. chemical warfare amongst plants and plants and rhizosphere organisms. It is based on the toxicity or signal character of specific root exsudates and helps plants to design a microenvironment of their own around their roots and shoots.