Hydroponics[1] is a type of horticulture and a subset of hydroculture, which is a method of growing plants, usually crops, without soil, by using mineral nutrient solutions in an aqueous solvent.[2] Terrestrial plants may be grown 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.[3] Despite inert media, roots can cause changes of the rhizosphere pH[4] and root exudates can affect the rhizosphere biology.[5]