I have heard of use of gibberelic acid to INITIATE (cause) bolting, mostly in artichoke production and in the production of long stem flowers for cutting. Search for +gibberellic +bolting.

I have read of using it prior to Camellia Blooming in the fall...

I haven't heard about using gibb to stop flowering or shoot extension. There are other chemicals on the markets for non-edible plants, materials meant to dwarf plants.

Coriander (cilantro) readily goes to flowering and seeding; however, in the US there are cultivars with names such as "Slo-bolt" (Johnny's Sel. Seeds) reputed to be slower to bolt.

I grow nine kinds of basil. All will start flowering early if stressed by climatic or watering extremes. I try to start them off well and pinch terminals starting when the plants are small so as to increase branching. I find the flavor of annual basils (Genovese, Neopolitino, Monstuoso, the various reds, and the licorice to be best at flowering. The perennials tend to be much stronger-flavored and seem to want to drop leaves as they go into flowering. But this last observation is preliminary. I am in my second year of side-by-side trials.

The American Camellia Society sells gib kits and has information about using gib for earlier, larger camellia blooms.

Here is a link that might be useful: American Camellia Society

There is a Gibberellic Acid (GA3) FAQ and ordering information at http://www.super-grow.biz/GA3FAQ.jsp

The best way to prevent bolting is to pinch back often.-Sandy

The commercial growth regulator, Arest, is a gibberellin antagonist, but it is not for use on food crops.

You might want to try Googles new beta product http://scholar.google.com/ and search for +gibberellic +bolting

Here is a link that might be useful: scholar.google

I think gibberellic acid is more likely to cause bolting rather than stop or slow it down. Kinetin might help as it encourages side growth as opposed to strong central growth . I would try 80ppm.

What about growing near a black walnut, is cilantro and/or basil Juglone sensitive?