Hairy roots culture
Hairy root culture is a type of plant tissue culture for produce of volatile compounds [122]. The formation of hairy root in plants or hair-like root structures is actually the result of a plant disease caused by a gram-negative bacterium called ”Agrobacterium rhizogenesis”. These roots are used as a source for the production of aromatic and volatile substances [123]. Basically, the importance of hair roots is due to their rapid growth without the need for an external auxin [8] and their rapid growth compared to conventional roots. They produce volatile compounds at levels and patterns similar to natural roots, but secondary metabolites or volatile compounds are also produced in the airy parts of the plant. The efficiency of this method is higher than cell culture and by the ingress of abiotic or biotic elicitors in the culture medium, this efficiency can be further increased [116].