Auxins: Chemical nature, Biosynthesis, Bioassay, Physiological effects and Mode of action
Auxin:- > The word auxin is derived from a Greek word ‘Auxein’ which means ‘to grow’. > It is found in SAM, RAM and young leaves of plants. > Examples:- i. IAA (Indole Acetic Acid):- Only natural auxin ii. IBA (Indole Butyric Acid) iii. NAA (Naphthalene Acetic Acid) iv. 2,4-D (2,4-Dichlorophenoxy acetic acid):- a weedicide v. 2,4,5-T (2,4,5-Trichlorophenoxy acetic acid) vi. PIC (Picloram) vii. PCPA (p – Chloro Phenoxy Acetic acid) 1. Discovery of Auxins:- Auxin was discovered and named by F. W. Went in 1928 by performing Avena curvature test. It is a bioassay for auxin-type growth regulators. The coleoptile stump of a decapitated seedling will curve in darkness after a small gelatin block containing auxin is placed on one side of a straight coleoptile stump. 2. Chemical Nature of Auxins:- Auxin is an indole derived phytohormone which is weakly acidic. It has an unsaturated ring structure. Auxins belong to a group of hormones that have i...