Hydroponics is a type of horticulture and a subset of hydroculture which involves growing plants without soil, by using mineral nutrient solutions in an aqueous solvent. Terrestrial plants may grow with only their roots exposed to the nutritious liquid, or, in addition, the roots may be physically supported by an inert medium such as perlite, gravel, or other substrates. Despite inert media, roots can cause changes of the rhizosphere pH and root exudates can affect rhizosphere biology.
