Plant Growth Regulators

Gibberellin Inhibitor Abscisic acid (ABA)

Plant hormones (phytohormones) are physiological intercellular messengers that are needed to control the complete plant lifecycle, including germination, rooting, growth, flowering, fruit ripening, foliage and death. In addition, plant hormones are secreted in response to environmental factors such as abundance of nutrients, drought conditions, light, temperature, chemical or physical stress. Hence, levels of hormones will change over the lifespan of a plant and are dependent upon season and environment.
The term “plant growth factor” is usually employed for plant hormones or substances of similar effect that are administered to plants. Growth factors are widely used in industrialized agriculture to improve productivity. The application of growth factors allows synchronization of plant development to occur. For instance, ripening tomatoes can be controlled by setting desired atmospheric ethylene levels. Using this method, fruits that are separated from their parent plant will still respond to growth factors; allowing commercial plants to be ripened in storage during and after transportation. This way the process of harvesting can be run much more efficiently. Other applications include rooting of seedlings or the suppression of rooting with the simultaneous promotion of cell division as required by plant cell cultures. Just like with animal hormones, plant growth factors come in a wide variety, producing different and often antagonistic effects. In short, the right combination of hormones is vital to achieve the desired behavioral characteristics of cells and the productive development of plants as a whole.

Traditionally five major classes of plant hormones are listed: auxins, cytokinins, gibberellins, abscisic acid and ethylene. However as research progresses, more active molecules are being found and new families of regulators are emerging; one example being polyamines such as putrescine or spermidine.
Note that this classification is based partially on the chemical structure and partially on the commonalities of plant physiological effects that certain substances exhibit. Members of one class may not relate from a structural point of view to another. Auxins for instance include not only many indole 3- carboxylic acid derivatives but numerous phenylacetic acids as well. Most cytokinins (such as zeatins) are derivatives from adenine but still differ widely in their chemical structure. Hence, the mechanism driving action may be different in each case and likewise each specific activity will differ also. This is demonstrated by the range of optimal concentrations required for different factors which spans many decimals (0.001 – 100 mg/L).

Other Plant Growth Regulators:


Ethylene is unique in that it is found only in gaseous form. It induces ripening, causes leaves to abscess and promotes senescence. Plants often increase ethylene production in response to stress and before death. Ethylene concentrations fluctuate with the seasons while playing a role in inducing foliage and ripening of fruit.


Polyamines are unique as they are effective (and are applied) in relatively high concentrations. Typical concentrations range from 5 to 500 mg/L. Polyamines influence flowering and promote plant regeneration.

Selection of Biosynth polyamines
Cat.No. - Product Name
B-3250 - N,N'-Bis(2-aminoethyl)-1,3-propanediamine
P-7990 - Putrescine, free base
P-8000 - Putrescine dihydrochloride pure
S-7300 - Spermidine
S-7320 - Spermidine trihydrochloride
S-7400 - Spermine
S-7420 - Spermine dihydrate
S-7500 - Spermine tetrahydrochloride

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