3.  Induction of organogenic differentiation

Induction is a multistep process. A schematic representation of adventitious shoot proliferation from leaf-disc culture is presented in (Figure 5.5). A series of intracellular events, collectively called induction, occur before the emergence of morphologically recognizable organs.

Figure 5.5: A schematic representation of in vitro adventitious shoot proliferation from leaf-disc                      culture

 

Under the optimal growth regulator combinations, the cells induced to form a specific organ and would continue to develop into that organ even if the inductive growth regulators are removed. Hence, induction favours the irreversible commitment of cells to follow a particular developmental pathway. For example, Brassica juncea, undergoes the induction of organogenic differentiation where a cytokinin, BAP induces shoot-bud differentiation at the cut end of the cotyledon petiole. In the absence of BAP (basal medium) only roots are formed at the same site. The cotyledons transferred to basal medium after 11 days of incubation on BAP leads to the development of only shoots and no roots. Similarly, the cotyledons lose the potential to form shoots on BAP medium if they are pre-cultured on BAP free medium for more than 7 days.