The ability to follow different pathways in response to environment or phases of life to form different kinds of structure is called plasticity. For example heterophylly in coriander.
Auxins are of two types :
(1) Natural auxins : These are naturally occuring auxins, isolated from plants and are regarded as phytohormones e.g. IAA. NAA etc.
(2) Synthetic auxins : These are synthesized by artificially e.g. IBA 2,4-D etc.