Root - Plant Growth Substances

Induction of roots by auxins in stem cuttings is a well known phenomenon. The concentrations needed are much lower as compared to that which promotes shoot growth. Auxins also induce lateral root growth at lower concentrations. High concentrations of auxins are inhibitory to root growth. The auxin transport is basipetal in nature. Produced in shoot apex and lateral active shoot buds-auxins percolate towards roots. Obviously, the concentrations that reach roots are low.

The presence of cytokinins is a must for promotion of cell division in root tips. Cytokinins also interact with auxins in the cellular differentiation to produce roots and shoots. Gibberellins do not seem to be having much role in root growth. Ethylene plays vital role in affecting the nastic responses and geotropism. It also promotes dormancy in buds.