It is a generic term for chemicals that typically stimulate cell elongation, but auxins also influence a wide range of growth and development response.
The chemical isolations and characterization was done by Kogi et al. (1934).
Auxins are the first identified hormones of which IAA seems to be the major naturally occurring, endogenous auxin in crops.
Besides IAA, plants contain three other compounds which are structurally similar and elicit many of the same response as that of IAA, 4, chloroindole acetic acid (CIAA),phenylacetic acid (PAA), indole butyric acid (IBA).
Synthetic compounds are classified into five major categories; indole acids, naphthalene acids, chlorophenoxy acids, benzoic acid and picolinic acid derivatives.
1
Cell divisions and enlargement Eg. cambial growth in diameter
.IAA + GA
2
Tissue culture
Shoot multiplications (IBA and BAP),callus Growth (2,4,-D), root multiplication IAA and IBA (1-2 mg)
3
Breaking dormancy and Apical dominance
NAA
4
Shortening internode
Apple trees (NAA) (dwarf branch-fruit)
5
Rooting of cuttings
(10-1000 ppm - NAA, IAA, phenyl acetic acid)
6
Prevent lodging
NAA- develop woody and erect stem
7
Prevent abscission
Premature leaf, fruit, flower fall (NAA, IAA and 2,4-D)
8
Parthenocarpic fruit
Grapes, banana, orange - (IAA)
9
Flower initiations
Pine apple -uniform flowering - fruit ripening (NAA). Delay flowering (2,4-D)
10
Weed eradications
2,4,D and auxin compounds
Preventing fruit abscission
Tissue culture: Callus growth and Shoot multiplication
