THE HISTORY, ORIGIN AND USES OF GIBBERELLINS
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 & 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, & 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.
EXPERIMENTAL DESIGN AND RECORDKEEPING
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. The aim of your research is 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 keep records on 3×5 cards, 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 are recorded on the card. Often we record the control test on the left side and the GA-3 test on the right side of the same card, for easy comparison. 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. Please share your results with us! Follow-up observations should include whether the plants develop, mature and bloom normally, since occasionally GA-3 will cause lifetime effects in the plant, as we have seen with the chinese cabbage mentioned. Also note that if GA-3 is used for many generations of a plant, this may cause natural selection and result in a strain that will not germinate without added GA-3.
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. Get this book!
THE 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. “This amount of GA-3 is about the amount that can be balanced on the 1/2mm tip of a toothpick using a type of toothpick that is pointed at both ends.” –Deno. This produces about a 1000ppm solution, and the outer pad is placed in a plastic bag and provides the humidity to prevent the inner pad from drying out. The amount of GA-3 can be varied as well as the time of exposure. The seeds can be germinated directly on the pad and removed as soon as they sprout to avoid overexposure. Advantages of this method are ease and extreme efficiency of use of GA-3. The disadvantage is variation in concentration of GA-3 due to difficulties ‘eyeballing’ the amount on the end of the toothpick. For slightly larger amounts of seed, I have used a paperclip with one end bent outwards and flattened with a hammer, and the tip bent at right angles to form a tiny scoop measuring slightly over lx2mm. A rounded pile of GA-3 on this is about 1 milligram, which is added to 1 ml (about 17 – 20 drops) to make 1000ppm. Again, everyone should get Deno’s book!
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.
PREPARING 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. Home measuring cups are often not accurate – I tested one with very accurate-looking scales on the side, and found it off by 20%! Good quality Pyrex glass measuring cups seem most accurate. 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. Some workers dissolve it first in a tiny amount of acetone or rubbing alcohol, then add the water. 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 dilutions 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. We have tested solution stored at room temperature for 4 years and found it fully active.
USING YOUR KIT
Read the Bertrand Method and the Deno Method, and decide which you want to use. If you use the Deno Method, do not prepare the solutions. Prepare a work area by laying down newspaper to catch spills. Each kit contains two bottles, marked 500ppm and 1000ppm. Each bottle has two marks on the side; at 50ml and 100ml in the small kit, and at 500ml and 1000ml in the large kit. Place the contents of one GA-3 package in the bottle labeled 1000ppm, and fill with water to the top mark. Shake or leave overnight till dissolved, making the 1000ppm solution. To prepare the 500ppm solution, pour half the 1000ppm solution into the other bottle, filling it to the lower mark. Add water to fill to the upper mark, making 500ppm. Store solutions away from sunlight, and out of reach of children.
In our adaptation of the Bertrand Method, the seeds are folded up in the filter paper circles, placed in the 2×2″ poly bags, and the appropriate solution added. Use enough to completely wet the seeds and paper and leave extra for the seeds to absorb. For larger amounts of seed, place in a culture tube and add solution to 1 1/2 times seed depth. Leave seed for 24 hours and add solution if needed. Most seeds absorb about their own weight, but some absorb much more, up to 20 times their own weight. Culture tubes should be kept horizontal to prevent seeds from jamming in the tube as they swell. After 24 hours the papers and seed are removed and blotted dry and sown as per the Bertrand Method, or germinated on toweling as per the Deno Method. Alternate dilutions can be prepared drop-wise with the dispo-pipettes, which average about 20 drops per milliliter, and are marked on the side in 1/10th ml increments. Best to mark your pipettes 1000, 500, etc. to prevent inadvertent mixing. The GA-3-1000 Advanced Kits include petri dishes for germinating seeds which require light on a pad of moist filter paper. Avoid excessive moisture.
OTHER AREAS FOR RESEARCH
Potassium nitrate (KNO3) is often used to stimulate germination of dormant or irregular seeds. It can replace the light requirement of some pines. The seeds are soaked in a 1000 to 3000ppm solution (1 – 3 grams per liter), or are germinated on pads soaked in this solution. Concentration is not crucial, so 1/4 to 1/2 teaspoon per quart is fine. It is about 6 grams per teaspoon. In our tests, some seeds which normally give seedlings over 3 months have all come up in a month with KNO3.
Hydrogen peroxide stimulates many species. Seeds are soaked in a 1 – 3% solution for 5 minutes to 48 hours for hard seeds. We have had very good results.
Presoaking seeds in malt extract solution or in beer may increase germination and vigor, especially of old seeds, due to enzyme enrichment. Higher resistance to damping off and higher yields have been reported. Other sources of enzymes include digestive aids (bromelain, papain, etc, available at health food stores), enzyme cleaners for contact lenses, and enzyme drain-cleaning products.
Citric acid is available in the canning section of the grocery, and has been used at 1000ppm to stimulate the germination of some species.
Sodium hypochlorite (household bleach) has been used in a 1% solution for a one-hour presoak to stimulate germination of some species. Mix one part bleach with 4 1/4 parts water for a 1% solution. A ten minute soak in one part bleach plus one part water is an FDA approved seed disinfectant.
Smoke and charred-wood leachate (water in which charred wood has been soaked) may stimulate germination of plants from fire-prone habitats with hot, dry summers, such as the Mediterranean, California, South Africa and Australia.
GA-3 is sometimes used in very low concentrations, from 1 ppm to 150 ppm, to promote the germination of non-dormant seeds such as rice.
Combined treatments such as KNO3 plus GA-3, or hydrogen peroxide plus GA-3 have given higher germination than either treatment alone. Testing these substances in various combinations is enough for a lifetime of interesting research!
SAFETY
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.
Reporting this information does not imply our endorsement of animal testing!
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.
BIBLIOGRAPHY
Deno, N. 1993. Seed Germination, Theory and Practice, Second Edition. Availability.
Takahashi, N., B. Phinney & J. MacMillan, Editors. 1991. Gibberellins. SpringerVerlag, New York.
GA-3 Quick-Start Instructions
Gibberellic Acid (GA-3) is safe and easy to use. If you want to get started right away, before reading the full instruction sheet, here is how. Some people have written that the full instruction sheet is needlessly complicated or intimidating, and they didn’t feel ready to use GA-3 on their seeds. Sorry! Don’t let my overly-scientific instructions keep you from trying it. It can all be summed up as:
1) Make the 1000 ppm stock solution, and the 500 ppm dilution.
2) Soak seeds overnight in one of these solutions.
3) Plant like any other seeds, and watch them grow. Easy!
Start by making your 1000 ppm (parts per million) stock solution. This is done by dissolving a 100 mg packet of GA-3 powder in 100 ml of clean water. This is a little less than 1/2 cup. If you have a 1000 mg (1 gram) packet of GA-3, add it to 1 liter (about 1 quart plus 1 cup water). If you have one of our kits, add the GA-3 powder to the container marked “1000 ppm”, and fill with clean water up to the top mark on the side. Distilled or purified water is best, but most tap water is fine.
GA-3 takes a while to dissolve — overnight if you use cold water. If you are in a hurry, you can use hot water, or you can put the GA-3 powder in the container and add a teaspoon or so of rubbing alcohol. With frequent swirling, it should dissolve in a half-hour or so. Then add water up to the top mark. You can check to see if it is fully dissolved by shining a light up through the bottom of the container and swirling it to see any undissolved crystals.
While waiting for the GA-3 to dissolve, why not read over the full information sheet? It will increase your success starting seeds.
This is your 1000 ppm stock solution. To make the 500 ppm dilution (which is used most), just mix equal parts of the stock solution and water. If you have one of our kits, fill the 500 ppm container up to the lower mark with your stock solution, and then add water up to the top mark.
You don’t need much of the solution to soak your seeds — just enough for the seeds to fully swell. Most seeds can be soaked in the small poly-bags (in the kits). Tiny seeds should be folded up in a filter paper for ease of handling when soaking. Larger seeds can be soaked in a pill bottle, small jar, or one of the culture tubes supplied in the kits. Use the stronger stock solution on very hard to germinate seeds, and the 500 ppm on seeds that are just hard or slow to start. Don’t use it on easy to start seeds unless you dilute it greatly. Normal, easy-to-sprout seeds will become very elongated and stretched out, then die if GA-3 is used on them. Use it on hard-to-start seeds only.
Is GA-3 Natural and Organic?
GA-3 is a naturally-occurring plant growth regulator. It is a completely natural, organic substance that is present in many plants, and in fact is essential to certain life-processes in many plants. There is absolutely, positively, nothing unnatural about it. It is produced by growing a naturally-occurring fungus in large vats and extracting the GA-3 from it. It is NOT produced synthetically by any chemical process, but is EXTRACTED from a plant (fungus), so it is just like many vitamins which are extracted from plants, or penicillin which is extracted from fungus. Its chemical structure is not changed in any way. Yes, it is sold under the chemical name, so it SOUNDS “chemical” but is no less natural than the vitamin C that is extracted into the water of a cup of rose-hip tea, or the vitamin E extracted from wheat germ. For example, “2,5,7,8-tetramethyl-2-(4′,8′,12′-tetramethyltridecyl)-6-chromanol” sounds like something you would not want to put on your garden, but this is just the chemical name for vitamin E.
GA-3 is NOT produced from a GMO as far as we know – we would very much doubt it, since it has been produced abundantly by the natural fungus for many decades, and there would be no reason to GMO it.
It is more natural than aspirin (a semi-synthetic) and safer than vitamin A. If you ate an ounce of pure vitamin A it would kill you!).
GA-3 is APPROVED BY MOST ORGANIC CERTIFYING ORGANIZATIONS. Commercial GA-3 formulations such as Pro-Gibb are certified by OMRI, the Organic Materials Review Institute – contact them at info@omri.org or (541)343-7600.
We cannot imagine that any organic certifying organization would not allow GA-3 for use in stimulating difficult seed germination. It is used in such microscopic quantities for this purpose – only a few micrograms enter the seed and it is utilized in the seed’s growth so will not persist in the plant. In fact it is produced in many seeds by natural processes which break dormancy. Prohibiting it would be a crazy as banning putting seeds in your refrigerator to break dormancy, because this is “unnatural” cold, and since this will trigger GA-3 production within the seed. No matter how organic and careful you are, far more toxic chemicals are entering your growing grounds from air pollution and toxic rain, or leaching out of plastic pots or plastic or metal irrigation lines or even from the soles of your shoes. Pollution is a global reality for the entire biosphere. Pesticides have even been found in Antarctic ice. No portion of the planet is free from man-made toxins. GA-3 is already in many natural seeds and plants and compost on your land, and its use to help the germination of rare and difficult seeds has such great conservation value by helping to propagate these plants that its use is clearly justified. It is currently being used to help germination of endangered species in order to build up their populations, and to help propagate medicinal plants which are threatened by over-collection from the wild.
We now have a single report that one grower has been prohibited from using GA-3 to stimulate seed germination by her biodynamic certifying board. If your organic or biodynamic certifying organization will not allow you to use GA-3 to stimulate seed germination, please object strongly and have them contact us for more information. Point out to them that such a prohibition is extremely counterproductive and only serves to discredit organic and biodynamic methods. We are very interested to hear any reasons given for such prohibition. We are very interested to see any evidence that that the use of GA-3 for stimulation seed germination is in any way “unnatural” or harmful. We welcome open and productive discussion of this matter with any certifying organization.
