1. They bring growth.
2. They stimulate cell division.
3. They bring opening of stomata.
4. They check abscission of leaves except ethylene.
5. They break seed dormancy.
6. They induce formation of fruits and flowers in all types of plants.
7. Gibberellins overcome vernalization.
Inhibitor hormones :
1. They retard growth.
2. They inhibit cell division.
3. They bring closing of stomata.
4. They bring abscission of leaves.
5. They induce seed dormancy.
6. They generally do not induce fruit and flower formation.
7. They have no impact.
Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedling.
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.