There are five major classes of
plant hormones (a.k.a.
Plant growth regulators (Pgr's)) with perhaps a few others as candidates to take that place in the future. The five major hormone classes are
Auxins[?],
Cytokinins[?](CK’s),
Ethylene,
Gibberellins[?] (GA’s), and Abscisic Acid (ABA). Recently it has been suggested that
Brassinosteroids[?] (BA’s),
Jasmonates[?] (JA’s),
Salicylates[?] (SA’s), and
Polyamines[?] are new classes of major hormones.
° See also: Hormone