Plant Growth Regulater
The five primary plant growth regulators are auxins, cytokinins, gibberellins, abscisic acid and ethylene. Each plant growth regulator functions in different ways. For instance, Auxins induce calli. Cytokinins stimulate cell division. Gibberellins induce organogenesis especially in adventitious roots. Abscisic acid favors maturation and germination. And ethylene is the main regulator for fruit ripening.
Below are the common PGR actions when added in vitro.
Auxins
- Induce callus (mass of undifferentiated cells) from explants (the portion of plant tissue used in culture techniques)
- Favors root and shoot morphogenesis (biological process that causes a cell, tissue or organism to develop its shape)
- Are more effective combined with cytokinins
Cytokinins
- Stimulate cell division
- Release of lateral bud dormancy (inactivated bud)
- Induce adventitious bud formation
- Often inhibit embryogenesis and root induction
Gibberellins
- Induce organogenesis, particularly adventitious roots
- In some cases, inhibit shoot, root, and embryo formation
Abscisic acid
- Favors maturation and germination of somatic embryogenesis
- At high concentrations, inhibits callus growth and organogenesis (buds, roots, embryos)
- Favors the maturation and normal growth of somatic embryos
- Increases freezing tolerance of grown plants and cell cultures
Ethylene
- It is less frequently used as it is naturally produced in all plant cultures
- When it is used, it promotes the maturation of tissues
- Depending upon the time after subculture, ethylene can stimulate or inhibit growth and organogenesis
- Affects growth of callus and suspension cultures, stem and root elongation, axillary and adventitious bud formation, rooting, and embryogenesis.
