- The Five Major Plant Growth Substances
|
Hormone |
Main Functions |
|
Auxins |
Stimulate cell elongation and differentiation; promote apical dominance; retard leaf fall |
|
Gibberellins |
Stimulate stem elongation; promote fruit/seed development; promote seed germination |
|
Cytokinins |
Promote cell division; modify apical dominance (promote lateral bud growth); promote germination; retard leaf senescence (aging) |
|
Abscisic acid (ABA) |
Inhibits growth; promotes seed dormancy; inhibits early germination; promotes leaf senescence |
|
Ethylene |
Promotes fruit ripening; promotes lateral expansion; inhibits elongation; promotes leaf fall (abscission) |
Interactions Between Hormones
- Synergism: growth substances that reinforce each other’s effect when acting together, e.g. auxins and gibberellins.
- Antagonism: growth substances that work in opposite/opposing effects, e.g. auxins and abscisic acid.
- Florigen: a hypothetical phytohormone believed to be involved in triggering flowering.