Cell cultures
It seems each cultured cell has all the genetic information of the parent plant and therefore has the ability to produce a range of chemicals found in the parent plant [8]. Through this culture, the desired volatile compound can be prepared. Some plants are rare, slow-growing or difficult to grow, so the in vitro under controlled condition is expected to accelerate biomass propagation and provide the essential oil [119]. The yield of this method is influenced by the factors of nutrients and growth regulators of the culture medium such as: sugar, nitrogen, phosphate, growth regulators, precursors and suitable culture medium [120]. But the compounds obtained by this method have low efficiency (0.01–0/1 g/l day.) [119]. The reason for the reduction in the production of plant compounds by cell cultures is not yet clear. [116]. So in general, this method does not seem to be a promising method, even with effective agents.