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GA-3 Sources

to Philip Stevens:

The following is an adaption of an email I sent out to the Alpine-L group a
month ago on the same subject:

A horticultural supplier for GA3 would be Carolina Biological Supply Co,
2000 York Road, Burlington, NC  

Some clarification on its effective use is needed for those of us who do
have access to the pure compound:

Baking soda (sodium bicarbonate) or some other base is needed to form a
soluble salt.  Potassium bicarbonate or weak ammonium hydroxide should work
as well.  Dissolve the acid in its own volume of the bicarbonates in a small
amount of water.  For ammonium hydroxide, add a few drops at a time with
stirring to a slurry of the acid in water until it dissolves.  Take these
concentrates and dilute to the required strength.

An important point:  don't make more of the solution up than you can use in
a month, and keep it refrigerated.  Common bacteria found in tap water will
consume it as a food source, thereby weakening its potency.

Chemical and drug supply house require an established account for access,
which most members do not have.  For those who do have access to these
accounts, one source is Aldrich Chemical Company.  The product ID number is
G85-4, and one gram will cost over $20.  Sigma Chemical also sells it (P.O.
Box 14508, St. Louis, Missouri 63178).  You will  need a micro balance to
weigh it accurately. 

As a natural products chemist, I recommend the avoidance of all forms of GA
with the term methyl ester in them:

Gibberelic Acid Methyl Ester
Gibberellin A1 Methyl Ester
Gibberellin A3 Methyl Ester 3,13-Diacetate
Gibberellin A4 Methyl Ester
Gibberellin A5 Methyl Ester
Gibberellin A7 Methyl Ester
Gibberellin A9 Methyl Ester

In layman's terms, this will mean that they won't dissolve well in water: a
free acid group is needed, and it must be turned into a  water-soluble salt
to work.

The ones listed below will dissolve in water with a base:

Gibberellin A3 3-Acetate
Gibberellin A9

The problem of supply for most members should be solved by using
commercially available preparations designed for horticultural use.  They
will either be soluble salts, or can be made soluble with baking soda.  The
Merck Index notes that GA4 and GA7 as well as GA3 are used commercially for
these purposes.  I would avoid anything else, since they may not have the
intended effects and will prove more expensive.

Rich Dufresne
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