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PLANT HORMONES AND GROWTH SUBSTANCES
DEFINITIONS, TYPES AND PROPERTIES

Hormone - an endogenous or naturally-occurring compound that is produced or synthesized in one part of the plant and causes a change in physiology, growth or development in another part of the plant; usually present in very small quantities.

Growth Substance - all naturally-occurring or synthetically produced substances that affect the physiology, growth and development of plants.
 
Naturally-Occurring
Example
Synthetic 
Example
Structure
Site of Production
.
Auxin
  • indoleacetic acid (IAA)
  • indolebutyric acid (IBA)
  • naphthaleneacetic acid (NAA)
  • 2,4-dichlorophenoxyacetic acid (2,4-D)
  • shoot tips
  • embryos
.
Cytokinin
  • zeatin 
  • kinetin (not in plants)
  • benzyladenine (BA)
  • pyranylbenzyladenine (PBA)
  • root tips
  • embryos
.
Gibberellic Acid (GA)
  • over 70
  • none
  • shoot tips 
  • root tips 
  • embryos
.
Ethylene
  • ethylene
  • ethephon or ethrel

    • (both release ethylene inside plant)
  • ripening fruits
  • aging flowers
  • germinating seeds
  • wounded tissue
.
Abscisic Acid (ABA)
  • abscisic acid
  • none
  • plastids, especially

    • chloroplast