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Seedman's Gibberellic Acid-3 (GA-3)

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We would like to thank the folks at JL Hudson Seeds for the useful information that they have published over the years concerning the use of GA-3, much of the information below is a result of their publications.

Free Download of N.C. Deno's Seed germination, theory and practice.

We no longer offer the Gibberellic Acid Kit we made available in the past, but we still offer Gibberellic Acid Powder for our customers to experiment with.

Gibberellic Acid-3 (GA-3) is a naturally occurring plant growth regulator which may cause a variety of effects including the stimulation of seed germination in some cases. GA-3 occurs naturally in the seeds of many species and is produced commercially by growing Gibberella fujikuroi fungus cultures in vats, then extracting and purifying the GA-3.
Presoaking seeds in GA-3 solution will in many cases cause the rapid germination of many types of highly dormant seeds which would otherwise need cold treatment, after-ripening or aging, Or other prolonged pretreatments. Many different types of dormancy are overcome with GA-3, and excellent results are obtained with many ordinarily difficult seeds.
Not all seeds respond well. A great deal of research needs to be done to determine which species benefit, and the proper concentration of GA-3 for each type. We are pleased to offer the GA-3 kits at the bottom of this page which contain everything you need to presoak seeds and study GA-3 effects.

GA-3 is safe to use. It is naturally present in many foods, is routinely sprayed on food crops, and is approved by most organic certification programs.

We sell this product for the study of seed germination only.

Gibberellins were discovered by Japanese plant pathologists studying "bakanae" disease ("foolish seedling") of rice, in which seedlings grow elongated and die. In 1898 Shotaro Hori demonstrated that it was caused by a fungus, now known as Gibberella fujikuroi. In 1926 Eiichi Kurosawa reported that a chemical produced by the fungus caused the symptoms, and that the substance was heat-resistant, not losing its activity after 4 hours at 100°C (212°F). In 1935 Teijiro Yabuta first isolated a non-crystalline solid and named it Gibberellin. In 1938, Yabuta and Yusuke Sumiki first isolated a crystalline compound from the cultured fungus.

Since this time, 79 different gibberellins have been isolated, many of these from the seeds of a wide variety of species. Gibberellic acid-3 (GA-3) is the most widely used, and is produced commercially by growing the fungus in huge vats and then extracting and purifying the GA-3.

Many different gibberellins are present in common plants. Rice contains fourteen GAs, and rice anthers contain up to 3.4 micrograms of GA-4 per gram fresh weight. Maize (corn) seed contains twelve GAs, maize pollen 9 GAs, wheat and barley contain 5, and 4 day old wheat seedlings contain 11. GAs are produced in the roots of onions and act as bulb suppressants, preventing the swelling of the bulb until the proper time. GAs control sex differentiation in cucurbits, spinach, hemp and maize. GAs control shoot elongation in many plants, and dwarf forms of some plants are due to GA deficiencies. Developing peach seeds are rich in GA-32 and extracts have been used to induce flowering in Xanthium and Perilla. Ferns produce GA-related compounds called antheridiogens which trigger antheridia formation.

Gibberellins are used in agriculture for various purposes. GA-3 is sprayed on seedless grapes to increase grape size and yield, and it is used on navel oranges, lemons, blueberries, sweet and tart cherries, artichokes and other crops to decrease or increase fruit set, delay rind aging, etc. These effects are highly dependent on concentration and stage of plant growth. For example, 0.02 micrograms GA-3 promotes flowering of dwarf Ipomoea nil, but 2 - 20 micrograms inhibits flowering. Ten micrograms of GA-3 applied to pea seedlings nearly doubled shoot length if applied at 3 days old, but barely affected 9 day old seedlings. GA-3 and GA-13 trigger female cone formation in almost all Taxodiaceae and Cupressaceae-- an 8 month old seedling of Sequoiadendron produced a female cone after weekly GA applications. Extremely small amounts of GAs may cause effects- as little as 2 nanograms (billionths of a gram) can trigger cone formation in a Cupressus arizonica shoot-tip. The Pinaceae do not form cones with GA-3, but need GA-4, 7 and 9. This property is used to speed up tree-breeding programs. GA is used to trigger flowering of sweet potatoes in breeding programs, to help tomatoes set fruit at high temperatures in the tropics, and to stimulate flowering in the Araceae, such as in breeding taro. GA-3 applied to seed of Chinese cabbage overcomes the need for chilling or long days to trigger flowering, so is used in the tropics for breeding.

Developing seeds are active sites of GA biosynthesis, and studies have found increases in GA levels in seeds during cold treatment and germination. The germination of old seeds has been improved with use of GA. Applied GA-3 may trigger dormant seed germination, in many cases overcoming the need for special or prolonged dormancy-breaking conditions such as cold. treatment, light, after-ripening, etc. We have designed these kits for the study of this effect.

Experimenting with GA-3 While many ordinarily difficult seeds will readily germinate using GA-3, it may kill other seeds or produce badly etiolated (elongated) seedlings that will not survive. Some species will be killed by 1000ppm (parts per million), not affected by 500ppm, but 750ppm will produce healthy seedlings. More research is needed by gardeners like you to determine which species benefit, and what treatment will produce healthy, normal seedlings and plants.

Each type of seed should have a control, a test of untreated seed to compare against the GA-3 treated test. Otherwise, you will have no way of knowing whether GA-3 made a difference. We suggest you keep a record, with the name of the plant, seed source and date or year of harvest, the number of seeds tested, the treatment given, and the date test begun. As the seeds germinate, the number of seedlings, their condition and the date should be recorded. Once GA-3 is found to help a particular species, the next step is to test different concentrations to find the best solution to use.

Your best source of information on using GA-3 to stimulate seed germination is Seed Germination, Theory and Practice, available for $20.00 postpaid worldwide from the author: Dr. Norman C. Deno, 139 Lenor Dr., State College, PA 16801 USA. We wish every one of our customers would get this book - it absolutely will increase your success with seeds. It reports the results of testing over 4000 species, and a supplement is available.

The folks at JL Hudson list the following methods of using Gibberellic Acid-3 (GA-3) for tests:

1. The Norman Deno Method
Developed by Dr. Norman Deno, this method dispenses with making stock solutions, so you may store the powdered GA-3 for long periods, and avoid discarding unused solution. For full details you should consult Deno's book. Briefly, a high wet-strength paper towel is folded in half 3 times to give a pad about 2 1/2 x 4 1/2" and is moistened with water. The last fold is opened, and a 3 x 3" piece of polyethylene cut from a plastic bag is placed in the center. A 2 1/2 x 2 1/2" piece of toweling is folded into a pad 1/2 x 1" and moistened with about 6 drops of water, and this is placed on the polyethylene. The seeds are placed on this inner pad and 1 cubic millimeter of the GA-3 powder is sprinkled on the pad.

2. The Bertrand Method
Developed by Stephen Bertrand, proprietor of The Perennial Flower Farm in northern Iowa, this is an efficient method for treating large numbers of seeds. Unbleached or oxygen-process whitened (chlorine-free) coffee filters are cut into 3" squares (larger for larger amounts of seed), and folded diagonally. The seed is placed in the center, the ends folded towards the center, and the top folded over and tucked in (jewelers fold). The name of the seed or a number can be written on the fold with indelible pen. GA-3 solution is placed in the wells of a small plastic cocktail-type ice cube tray (the type for tiny cubes), or in a regular ice cube tray for large amounts of seed. Each seed fold is placed in a well to wick. up the solution. If different concentrations of GA-3 are being tested at the same time, only every other well is used, to prevent cross-mixing. After 24 hours the folds are removed, blotted dry on a pad of toweling, and either sown or placed in new folds for pre-chilling (cold treatment) as described in Deno's book. The advantage of this method is that the GA-3 concentration can be accurately controlled, a necessity for certain seeds. The disadvantage is that the solution will eventually break down, resulting in decreasing concentrations or waste of solution.

We have simplified these methods by acquiring petri dishes with disposable pads, and offering premixed packs of Gibberellic Acid-3 (GA-3), ready to mix with water, more about that later.

Safety in Experimenting with GA-3 GA-3 is a natural organic compound, and its use is approved by most organic certification agencies.

GA-3 is considered 'relatively non-toxic'. According to the MSDS (Material Safety Data Sheet), the LD50 (lethal dose 50) or the dose which kills 50% of the test animals, is 1000 to 25,000 milligrams per kilogram of body weight in mice, dogs and rats. Applied to humans, this would mean a 75 kilogram (165 pound) person could be killed by consuming between 75 and 1875 grams (2.6 ounces to about 4 pounds) of the 90% GA-3 powder. "In reproductive studies in rats, no maternal or fetal toxicity, or other adverse effects to the fetus were noted following large doses (1000mg/kg/day) of Gibberellic acid." --MSDS. The powder may cause eye irritation; in case of contact, flush with plenty of water.

The relative non-toxicity of GA-3 and its use on food crops should not encourage careless handling - always keep out of reach of children, avoid contact with skin, eyes and clothing, wash hands after using, or use rubber gloves. Do not use on food crops or for any other purpose than seed germination research. Properly dispose of toweling or filter papers after use, thoroughly wash implements, then rinse with vinegar, then rinse again.

Do not contaminate soil - GA-3 is highly persistent and bioactive and may remain in soil for some months and affect plant growth. A healthy organic soil with strong microbial growth will probably break it down fastest. Plants vary widely in their sensitivity to GA-3. Remember that while GA-3 is sprayed on table grapes at a rate of 1 milligram per 1.7 square feet (26 grams per acre), that same milligram could cause cone formation on 500,000 Cupressus shoots. Remember that while GA-3 is naturally present in common foods like corn, it is only in billionth of a gram quantities.

Making GA-3 Solutions The basic stock solution of 1000ppm (parts per million) is prepared by dissolving GA-3 in water at a rate of 1mg (milligram, one thousandth of a gram) in 1 ml (milliliter, one thousandth of a liter). Therefore, a 100mg packet is dissolved in 100ml of water or a little less than 1/2 cup (0.42 cup), a 500mg packet in 500ml (2.1 cups), or a 1000mg (=1 gram) packet in 1000ml (=1 liter, or about 1 quart plus 1 cup) water.
Distilled water is best. GA-3 is slow to dissolve and may need prolonged stirring. You can just stir it in, then leave it overnight and it should be dissolved by morning. Other concentrations are prepared by diluting this stock solution.
To make 500ppm, mix equal amounts of 1000ppm and water. To make 750ppm, mix equal amounts of 1000ppm and 500ppm. To make 375ppm, mix equal parts 750ppm and water, and so on. Tiny amounts of these dilution for individual tests may be made up drop-wise - five drops 1000ppm plus five drops water to make 500ppm, etc.

Many workers use 1000ppm for everything, but this may be too strong for many seeds. Stephen Bertrand, after many years experience using GA-3, reports that he uses 500ppm for most species, due to less trouble with excessive elongation of seedlings, followed by 1000ppm, and lesser amounts of the 750ppm and 375ppm solutions. With many seeds, he says that a few in each lot will etiolate (elongate excessively), and the trick is to find the solution giving the most healthy seedlings.

Solutions of GA-3 are said to break down with time or exposure to sunlight, so store in a dark place. Kept in the dark it stores for years.

Gibberellic Acid Powder