Plant cells have the ability to create cells for leaves, roots, and other plant parts and by using plant growth regulators we can manipulate their growth. Plant growth regulators, or PGRs, influence plant cells directly to make them grow roots, shoots, or callus in our cultures. Cells can be influenced to create various new growth in different stages of tissue culture. There are several types of PGRs commonly used for this: auxins, cytokinins, and gibberellins.
Cytokinins are the most important plant growth regulators used in tissue culture. Cytokinins are plant growth regulators that primarily create cell division.
BAP (6-benzylaminopurine) is very common and is useful for creating multiple shoots from one explant. It is responsible for turning one piece of plant material into a bundle of tiny plantlets. These plantlets can be divided and put into multiplication media to be further multiplied and divided exponentially.
Cytokinins do little to create root growth in most plants. When rooting in cultures occur most cytokinins have been completely utilized and metabolized out of the media by the plants. With the now lack of cytokinins, the plant starts to grow roots on its own under its own power.
Auxins are another popular plant growth regulator. Auxins primarily contribute to better rooting. Auxins limit side shoots and other similar shoot tip growth in favor of developing a root system. Plants that are hard to get rooted outside of cultures, in wet perlite, for example, could benefit from having Auxins put into the medium either in multiplication or a dedicated rooting medium. This could save a lot of time in production.
Gibberellins are worth mentioning here also because GA3 has a place in your tissue culture toolkit. GA3 treatments are useful for seeds to break dormancy in those seeds that need stratifying treatment whether it be cold or heat.
GA3 also regulates young shoots where it will control stem elongation by encouraging cell division and elongation. Auxins only stimulate cell elongation. This is why you will occasionally see GA3 in a plant protocol alongside other plant growth regulators.
Adventurous Root Formation
Adventurous shoot formation
Callus Formation and Growth
2,4-D Dichlorophenoxyacetic Acid
Inhibition of Axillary Buds
Adventitious Shoot Formation
Promotes Cell Division
Callus Initiation and Growth
Axillary Bud Break and Growth
Inhibits Leaf Senescence
Shoot elongation. Dormancy.
|Regulator||Molecular Weight||Dissolves in mg/l|
|ABA – Abscisic acid||264.3||1N KOH 3.78|
|BAP (BA) – 6-benzylaminopurine||225.3||Ethanol 4.44|
|2iP – 6-(γ,γDimethylallylamino)purine||203.2||1N KOH 4.92|
|2,4D – 2,4-Dichlorophenoxyacetic acid||221.0||1N KOH 4.52|
|GA3 -Gibberellic acid||346.4||iN KOH 2.89|
|IAA – indole-3-acetic acid||175.2||Ethanol 5.71|
|IBA – Indole-3-butyric acid||203.2||Ethanol 4.90|
|NAA – 1-Naphthaleneacetic acid||186.2||Ethanol|
|TDZ – Thidiazuron||220.2||1N KOH 4.54|
|Zeatin||219.2||1N KOH 4.56|