Combined
plant growth regulators in different concentrations were always added in order to
optimize proliferation ability and potential organ regeneration capacity. For instance,
asparagus shoot tips subculture experiment conducted by Shi et al. [1995] contained two
steps. At first, shoot tips were cultured on 1/2 MS + 0.05 mg·L-1 KT + 0.5 mg·L-1 NAA
medium for 7 days. Later on, they were incubated on medium consisted of 1/2 MS
+ 0.1 mg·L-1 KT + 1 mg·L-1 MET + 0.1% active carbon (AC). Through this way of
culture, 80% rooting rate was received after 23 days of incubation.