List five plant growth hormones and mention one important role of each.

1. Auxins — Auxins promote the growth of stem, roots and fruits by cell elongation.
2. Gibberellins — Gibberellins promote the growth of internodes by cell elongation.
3. Cytokinins — Cytokinins stimulate cell division.
4. Ethylene — Ethylene helps in ripening of fruits.
5. Abscisic acid — Abscisic acid induces dormancy of buds and seeds.