plant growth regulators

[Ray]

Several species in "probiotic" cultures are known to emit IAA as a metabolite, but I wasn't aware of GA.

The manufacturer of KelpMax recently updated some documentation:

A recently published independent study shows the first indications of biologically active Gibberellins and Brassinosteroids being detected in the seaweed extract. The report showed that low concentrations of ABA are also present.

Where previously cytokinins, auxins and polyamines were quantified, the aim of this new study was to quantify other groups of bioregulators, for instance Brassinosteroids and Gibberllins. It has been found that Brassinosteroids elicit a wide range of physiological responses including cell division, stem and root growth, flower and fruit development, seed yield and protection from stress.

It is likely that this cocktail of natural plant growth regulators, which may act individually or in concert, contribute significantly to enhanced growth and yield as well as improved responses to biotic and abiotic stresses when applied to most crops, thereby benefitting the end user.

Even more interesting (to me) is the fact that the samples tested were more than two years from extraction and packaging.

[naoki]

I guess this is the paper you are talking about (there may be no full access at the link).

Abscisic acid, gibberellins and brassinosteroids in Kelpak®, a commercial seaweed extract made from Ecklonia maxima - Springer

Thanks for letting us know about this! I'll need to read it. From my quick scanning, there seems to be fair variation from batch to batch. It mentions that time of harvest, moon phase, season etc influence the composition. I wonder if they are mixing different batches to minimize the variation.

It is good to know that GA in KelpMax is stable after 2 years. Different hormones have different stability. I believe cytokinins are relatively stable, but I didn't know about GA. Auxins are generally less stable, but you mentioned that they use some way to stabilize it. I wish the data were published.

Gibberelins are first isolated from fungus (see the top section of this wiki). So I'm guessing those microbes containing fungi could produce GA.

[MRay]

PGRs are often used in tissue culture (cloning not seed germination). There should be several articles along the lines of using them for suspension cultures, etc. You may even find a laboratory exercise online.

[MRay]

In the nursery setting, PGR is a term that can mean more than growth suppression (although that is a common use). Examples (there are many more): growth suppression (A-Rest, Bonzai, Apogee), flower stimulation (Pro-Gibb), rooting (Hormodin, Dip-N-Gro), and branching (BA). There are also products that that block or interfere with natural plant hormones (e.g. ethylene blockers).

[Fairorchids]

PGRs are used in plants like Hibiscus, which untreated want to grow 1-2" between leaves - and buds. Treated plants set leaves closely together, and bloom continuously.

This concept does not apply to orchids, which have to grow a new shoot (usually to maturity) to bloom once. In the Vandaceous & Phalaenopsis group it makes no sense either, as these typically will bloom from each leaf when well grown.

[MRay]

True. PGR use is more common with orchids in the laboratory setting than in the greenhouse. Still remember a professor who kept suspension cultures of orchids multiplying on a shaker. Today, he is working with native orchids and exploring techniques to store the germplasm in liquid Nitrogen.