- Term ‘auxein’ means to grow.
- Weak organic acid
- Found in the root & shoot tip.
- Shows polar movements: i.e., shoot tip downwards & root tip upwards.
- Charles Darwin & his son Francis Darwin: 1st reported the presence of auxin in the coleoptile of canary grass (Phalaris). They showed that the coleoptile started growing towards unilateral illumination (phototropism), while the decapitated coleoptile did not.
- F W Went: Performed the Agar block experiment in Avena coleoptile (oat). He decapitated the tip of Avena coleoptile and kept it on an agar block, he later replaced the tip with agar block, the coleoptile started growing towards the light.
- Went named it as ‘Auxin’.
- Kogl & Haagen-smith: Isolated it from human urine.
Indole 3-acetic acid (IAA) & Indole butyric acid (IBA).
2,4-dichloro phenoxy acetic acid (2,4-D), Naphthalene acetic acid (NAA) & IBA.