The main five groups of plant growth regulators (PGRs) are :
5. Abscisic acid.
Physiological functions of auxins are:
1. They help to initiate and enhance rootings in the stem cuttings.
2. They promote flowering in certain plants like pineapple.
3. They prevent the leaf and fruit drop at early stages. They promote abscission of older or mature leaf and fruit.
4. They induce apical dominance.
5. They are responsible for tropic movements.
1. They induce parthenocarpy in plants like tomatoes..
2. They are used as weedicides that kill dicotyledenous weeds.
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.