BC Growers Association

Growth Hormones

This is nothing more than a compilation of some gibberellic acid info I've found on the net.  We would appreciated any additional info anyone is aware of.  In time, I'll come back to this page and publish the any results.

Ga by John Riley

Hormones By Leo Write

Vic High's notes on using GA to induce self-pollination

Ga sources

GA by John Riley

Gibberellic Acid for Fruit Set and Seed Germination

John M. Riley

The following information is taken from a article by John M. Riley that appeared in the 1987 CRFG Journal (vol. 19, pp. 10-12). See the back issue information for price and ordering information.

The Germination Process

The first stage of germination consists of ingesting water and an awakening or activation of the germ plasma. Protein components of the cells that were formed as the seed developed, became inactive as it matured. After an uptake of water, the system is reactivated and protein synthesis resumes. Enzymes and hormones appear and begin to digest reserve substances in the storage tissues and to translocate the digested substances in the storage tissues to the growing points of the embryo. The sequence of the metabolic pattern than occurs during germination involves the activation of specific enzymes at the proper time and regulation of their activity.

Control is exercised by four classes of plant hormones: inhibitors such as abscissic acid which block germination; auxins which control root formation and growth; the gibberellins which regulate protein synthesis and stem elongation; and cytokinins that control organ differentiation. Ethylene is also believed to have a control function in some plants. Sometimes the last three controls are used together to crash through dormancy in germinating difficult seed.

Gibberellic Acid

Gibberellic acid (actually a group of related substances called gibberellins) was discovered as a metabolic byproduct of the fungus Gibberella fujikuroi, which causes the stems of growing rice to elongate so rapidly the plant collapsed. Synthetic forms of gibberellic acid are available commercially.

Gibberellic acid (GA) is a very potent hormone whose natural occurrence in plants controls their development. Since GA regulates growth, applications of very low concentrations can have a profound effect. Timing is critical: too much GA may have an opposite effect from that desired; too little may require the plant to be repeatedly treated to sustain desired levels of GA.

Effects of Gibberellic Acid

  1. Overcoming dormancy. Treatment with high concentrations of GA is effective in overcoming dormancy and causing rapid germination of seed. Concentrations of about 2 ppm can cause tubers to sprout earlier.
  2. Premature flowering. If a plant is sufficiently developed, premature flowering may be induced by direct application of GA to young plants. This action is not sustained and treatment may have to be repeated. Formation of male flowers is generally promoted by concentrations of 10 to 200 ppm., female flowers by concentrations of 200 to 300 ppm. Concentrations of more than 600 ppm markedly suppresses initiation of both male and female flowers.
  3. Increased fruit set. When there is difficulty with fruit set because of incomplete pollination, GA may be effectively used to increase fruit set. The resulting fruit maybe partially or entirely seedless. GA has increased the total yield in greenhouse tomato crops both as a result of increased fruit set and more rapid growth of the fruit.
  4. Hybridizing. Pollination within self-incompatible clones and between closely related species may some times be forced by the application of GA and cytokinin to the blooms at the time of hand pollination.
  5. Increased growth. GA applied near the terminal bud of trees may increase the rate of growth by stimulating more or less constant growth during the season. In a Department of Agriculture experiment, the GA was applied as a 1% paste in a band around the terminal bud of trees. Treatment was repeated three times during the summer. Walnut tee growth was 8.5 ft. for treated trees, 1.5 ft. for untreated trees.
  6. Frost protection. Spraying fruit trees at full-blossom or when the blossoms begin to wither can offset the detrimental effects of frost.
  7. Root formation. GA inhibits the formation of roots in cuttings.


Although GA is not listed as a "poison", the following precautions should be observed: Flush with water any GA that may get into the eye. Avoid skin contact if possible. If skin contact is suspected, wash with soap and water. Do not re-enter an area after spraying until the GA spray is fully dry. Avoid ingestion of GA.

The powder may be dissolved as specified below to give the desired concentration.
ml (cup)
50 125 2400 (10 1/2) Early flowering
200 125 600 (2 1/2) Early flowering
800 125 160 (2/3) Blossom set
2000 125 60 (1/4) Seed germination
1% paste 125 5 ml (1 tsp.) lanolin Growth promoter

© Copyright 1987,1997, California Rare Fruit Growers, Inc.

Hormones by Leo Wright



                  The power of gibberellins to accelerate growth, and to induce or
                 promote flowering, continues to fascinate both amateur botanists
                 and commercial flower growers. One gibberellin is gibberellic acid,
                 a natural hormone that can be readily extracted from common

                                      by Leo Wright

                 Auxins, cytokinins and gibberellins are the principle
                 growth-promoting hormones found in plants. All three control,
                 stimulate, inhibit or alter a plant's development to one degree or
                 another, depending upon the external environment. Auxins tend to
                 promote rooting, leaf and fruit retention and directional growth; and
                 cytokinins promote active cell mitosis, ion transport and general
                 plant vigour. Gibberellins are noted as the most powerful of the
                 growth promotors because they , increase internode spacing, induce
                 and promote flowering in many plants, and modify the flower sex
                 expression in some plants.
                 Investigations in Japan in the 1920's of the pathogenic rice fungus
                 Gibberella fujikuroi, which caused rice plants to grow abnormally tall,
                 led to the eventual isolation from the fungus of several types of
                 gibberellins or growth-promoting hormones, including Gibberellic
                 Acid (GA-3).

                 Gibberellins are well known to promote uniform growth through cell
                 enlargement. They cause plants to grow tall and elongated, with
                 light green leaves, and also stimulate seed germination and other
                 growth phenomena such as early flower formation.

                 Flower Induction and Promotion

                 In many plants flower formation is governed by internal factors; in
                 other plants it is controlled by precise environmental conditions.
                 Some plants initiate flowering after having undergone exposure to a
                 period of cold. In nature, these cold-requiring plants usually flower
                 in spring or early summer, after having been exposed to the cold
                 temperatures of winter.
                 In other plants, flower formation depends upon day length or
                 photoperiod. Basically, there are two principal photoperiodic plants -
                 'long-day' plants which flower when the day length exceeds a
                 certain minimal value which may vary from one plant to another, and
                 'short-day' plants which exhibit the opposite behaviour, flowering in
                 relatively short days when the photoperiod remains below a certain
                 maximal duration.
                 Under these conditions, long-day plants flower in summer when the
                 days are longer, and short-day plants flower in autumn and winter
                 when the day length drops below the critical maximum.
                 Then there are plants that are described as 'dual-day length' plants,
                 where they stay vegetative if grown on continuous long day or
                 continuous short day, but flower if exposed either first to long then
                 short days ('long-short-day' plants), or vice versa ('short-long-day'
                 plants). Most cold-requiring plants also have dual environmental
                 requirement, flowering if the low-temperature treatment is followed
                 by a long-day regime.
                 The phenomenon of cold requirement with regard to flower
                 formation is called 'vernalization', and that of day length control as
                 'photoperiodism'. The conditions conducive and nonconducive to
                 flower formation in a given plant type have been termed 'inductive'
                 and 'noninductive', and exposure of cold-requiring and
                 photoperiodic plants to inductive temperatures and photoperiods
                 are called 'thermo-induction' and 'photo-induction' respectively. In
                 cold-requiring and photoperiodic plants alike, the need for induction
                 may be absolute, whereby the plant will fail to form flowers
                 altogether unless given inductive treatment; or it may be facultative
                 whereby flowering will ultimately occur without induction, although
                 with greater or lesser delay.
                 The use of gibberellins for cold-requiring and long-day plants can
                 induce or promote flowering to one degree or another. Typical
                 gibberellin responses include larger blooms, stem elongation, flower
                 stalk elongation, and in some cases earlier flowering, which are all
                 desirable elements to commercial flower growers.

                 Typical Applications

                 When gibberellic acid is sprayed on gardenia or geranium flowers,
                 there is a 25% -50% increase in flower size. The treatment is used at
                 the rate of 5 mg/L (5ppm) at the time of first colour appearance.
                 The flowering of cyclamens can be accelerated by 4-5 weeks with a
                 single spray of gibberellic acid, at the rate of 50 mg/L (50ppm), 60-75
                 days prior to the projected flowerdate (Widmer et al. 1974). Higher
                 concentrations will result in adversely tall and weak flower stems.
                 More recently, Lyons and Widmer (1983) suggest applying 15 gms/L
                 (15ppm) of gibberellic acid to the crown of the plant below the
                 leaves, 150 days after seed is sown.
                 Gibberellins are popular with commercial growers to replace the cold
                 treatment or long night treatment of plants such as azaleas to induce
                 or force flowering. Standard cultivation techniques require
                 flower-bud induction with about six weeks of long-night treatment.
                 Once flower buds are established, a temperature of 70C (450F) or
                 lower is required for six weeks to ensure flower bud development.
                 After this, flowers are forced into bloom in 4-6 weeks. However, a
                 weekly spray treatment of gibberellic acid for five weeks, at a
                 concentration of 1000 gms/L (1000ppm), will result in earlier
                 flowering and larger blossoms. The five consecutive weekly sprays
                 should commence when flower buds are well developed after the
                 short-day treatment.
                 Hydrangeas, another cold-requiring plant, also respond favourably
                 to gibberellic acid. Using the same five-weekly treatment, the
                 concentration should be reduced to 5-50 gms/L (5-50ppm) to ensure
                 earlier flowering and larger blooms.
                 Gibberellic acid can also be used to delay flowering and to stimulate
                 rapid growth in plants such as geraniums and fuchsia. The treatment
                 requires weekly sprays at the rate of 250 gms/L (250ppm) for four
                 weeks. According to Carlson (1982), gibberellic acid can also be
                 used to produce tree-type geraniums and fuchsia when applied at
                 the rate of 250gms/L (250ppm) two weeks after potting, then once
                 weekly for five weeks.
                 It should be noted here that the precise function of applied
                 gibberellins to flower formation is not entirely clear since all plants
                 react differently to treatments, and in many cases gibberellins do not
                 promote flower formation.

                 Sex Expression

                 Flower sex expression can be modified in some plants by treating
                 seedlings with several growth-regulating substances. With the
                 exception of gibberellin, these substances tend to reduce the number
                 or suppress the development of staminate flowers, and increase the
                 number or accelerate the development of pistillate flowers. In
                 contrast, in the case of cucumbers, gibberellins increase the number
                 of staminate flowers on monoecious cucumbers (plants that have the
                 stamens and the pistils in separate flowers on the same plant), and
                 result in the formation of staminate flowers on gynoecious (female)
                 cucumbers which would otherwise only produce pistillate flowers.
                 The ultimate effect of a chemical on sex expression would be a
                 complete reversal of flower sex. To validate a flower sex reversal one
                 would have to replace the intial staminate stage with pistillate
                 flowers, or the pistillate stage with staminate flowers in monoecious
                 plants. It has been found that gibberellins will increase the number
                 of staminate flowers in monoecious cucumbers, resulting in the
                 formation of staminate flowers on gynoecious cucumbers which
                 would otherwise only produce pistillate flowers.

                 Extracting Gibberellic Acid

                 Although several types of gibberellin are found in plants as natural
                 hormones, Gibberellic Acid (GA-3) is the best known. While it is a
                 natural product of the Asian fungus that destroys rice,
                 growth-promoting substances that are either identical with, or
                 closely related to, gibberellic acid can also be found in common
                 plants such as cucumber, rock melon (cantaloupe), corn, peas and
                 beans, and it can be readily extracted in crude form by amateur
                 Edward Pinto, a student at St Peter's Preparatory School in Jersey
                 City, developed a simple and inexpensive procedure for extracting
                 gibberellic acid from common plants, which was reported in
                 American Scientific ( August 1967). As sources of materials, he used
                 the seeds of fresh cantaloupe (rockmelon), fresh wild cucumber, and
                 the dry seeds of corn, peas and three species of bean - pencil rod,
                 lupine and pinto. The cantaloupe and cucumber seeds were dried at
                 room temperature and chopped into particles about 3mm in diameter.
                 The procedure used 200 grams of finely chopped seeds which were
                 soaked for seven days in a solution of acetone (10 parts by volume),
                 isopropyl alcohol (5 parts), ethyl alcohol (2 parts), and distilled water
                 (5 parts), to give a total volume of 110 millilitres. The solution was
                 then poured off and the seed particles rinsed with 40 millilitres of a
                 solution consisting of equal parts of acetone and isopropyl alcohol.
                 The rinsing solution was then added to the first solution, and heated
                 to a temperature of 450C (1130F)WARNING: it should be noted that
                 the solution is highly flammable and must not be exposed to an open
                 flame. The heating procedure was continued until the residue
                 evaporated to the consistency of thin tar and was almost dry. The
                 residue was then taken and mixed with 100 millilitres of distilled water
                 and ethyl acetate.
                 According to Pinto, a key factor to extracting gibberellic acid is to
                 raise the pH of the water to about pH 8 (slightly alkaline) - at this pH
                 the gibberellins are soluble in water. The pH was achieved by adding
                 potassium hydroxide, or concentrated pH lower to the solution. The
                 mixture was then shaken for two minutes, and the water drawn off
                 and mixed with another 100 millilitres of ethyl acetate. This procedure
                 was carried out a total of three times.
                 Now the water was made acidic (pH3) by the addition of
                 hydrochloric acid - at this pH the gibberellins are soluble in ethyl
                 acetate. The solution of acidic water was added to 100 millilitres of
                 ethyl acetate. The water was drawn off and the procedure repeated
                 twice more, after which the ethyl acetate solution was dried to a
                 paste. The tarlike mass was then mixed with about 8 grams of lanolin.
                 The lanolin paste is the final product, and it is applied to plants as a
                 thin coat to the upper surface of each mature leaf, taking care not to
                 damage the plant.


                 The role of plant hormones is complicated biologically and
                 biochemically, and even today their roles are not fully understood.
                 What works for one plant does not necessarily follow for another. In
                 most cases it is which will signal a homonal response. When applied
                 externally, hormones will influence the organisation of the internal
                 chemistry of the plant cell, and the interaction among cells, but the
                 degree of interaction will still depend upon the plant specie, the
                 stage of plant development and the external environment.

                  First published in Practical Hydroponics & Greenhouses - July/August 1993 (Issue #11)

                              © Copyright Casper Publications Pty Ltd.
Vic High's comments:

                            Posted by Vic High on June 20, 1998 at 08:30:08
                                  In Reply to huh? posted by ?.

   Ok, I hope I clarify more than I confuse, here goes.

   First, to answer your specific questions, the stability of hermie offspring is completely dependant on
   the stability of the parent. If NL#9 is stable, then the offspring will be NL#9. If it is a hybrid or unstable,
   then the offspring will be variable. No different than breeding two NL#9 plants except that all offspring
   will be female and that you know the specific bud qualities of both parents.

   I've attempted the gib acid method using the same method as E R and got ugly plants with a few pollen
   sacs but no seeds. As previously mentioned, timing is everything. I will try again as well when work
   load isn't so big. I have unduced hermies through stress though.

   I accidently created hermies when I had to hide my garden in a moving truck for a few days. I can't
   remember exact period of time off of the top of my head but for 2 to 3 days plants remained in darkness
   with an excessive amount of ozone. They were 2 weeks into flowering. I ended up with many unwanted
   seeds that prooved quite useful.

   What I had in the truck were several romulan and also a couple romulan F1 hybrids. The father of the
   cross was a very robust but compact ruderalis type of plant . It was used to help me understand the
   genetics of romulan. Romulan is tall, lanky, with very tight buds that are way too sticky (haha). Dad
   came from a uniform seedline that was short, compact, and had large leafy buds with little crystal.

   First of all, the hybrids grew up looking more like dad than romulan mom except bigger. I attributed this
   more to hybrid vigour rather than mom's taller genes expressing themselves because they were the
   same shape but just bigger. Buds looked like father's seed line but were slightly tighter and they had a
   few more crystals but still looked very much like the big leafy buds from dad's line.

   Although none of the plants peviously displayed a tendancy to become hermie, only the hybrids were
   stressed into it this time. They didn't produce true male flowers but just developed stamens that grew
   out of the female buds. They pollenated both the romulan and themselves.

   This turned out to be a blessing in disquise. I just harvested the offspring and found the results quite
   interesting. They produced NO hermies.

   The seeds from the hybrids (kinda like a F2 generation) were still quite uniform and they resembled the
   seedline from the P1 dad (original dad). They did produce two minature plants though.

   Seeds from the romulan (3/4 romulan) were far more variable. They either grew tall (1/3 of them) or
   stayed short (2/3 of them). Of the tall, all but one had buds just like the romulan but with variable
   smells. Of the short plants, all but one had the leafy buds. One short plant had romulan buds.

   In summary, I found that bud quality and height were somewhat linked in romulan. I also found that the
   romulan traits were mostly recessive.

   As for hermie pollen, a distinction should be made between various hermies. A true hermie produces
   both male and female flowers. These stress induced hermies did not produce male flowers (only
   stamens) and don't think that they can be considered true hermies. The main difference is that they
   didn't produce hermie offspring.

Gibberellic Acid Sources

Posted by Firefly on March 18, 1998 at 14:54:13:

In Reply to: Re: giberyllic acid posted by Vic High on March 16, 1998 at 22:34:54:

 Dear Vic High:

 I have a source for Gibberillic Acid-3 kits that are made for treating hard-to-sprout seeds. You
 can buy it in varing amounts from this source. The gentleman and lady who run this *small*
 business ask that 'they not be put on the 'web' ' as they don't believe that 'digital technologies are
 good for personal freedom.' I *HOPE!* they won't mind this referral.

 To get their 1998 catalog send $1.00 U.S. to :

 P.O.Box 1058
 Redwood City, CA 94064
 U S A

 (See pg. 74 in the catalog.)

 (I did check two other sources that used to carry it, but they don't seem to any more....) Good
 Luck; Be Kind to Those Who Are Kind.

 Ps. thanks for the Dynogen info--wondered what that was and was thinking of buying some....

Dynogen "Super Plant Spray" - 0.005% Potassium Gibberalate
- is an aerosol form of gibberellic acid.
- its manufactured for "Shartel Marketing, Inc., Albertson, NY  11507
- purchased from Northwest Garden Supply in BC, Canada

Activol - .92 gram of biologically active isomer of gibberellic acid per tablet.
- Package contains 10 tablets.
- for use on sweet and sour cherries, and rhubarb roots.
- Actival is a registered trademark of Zeneca Ltd., England.
- Distributed in Canada by: Norac Concepts Inc., PO Box 40577, Burlington, ON  L7P 4W1

   gibberellic hormone spray
   miracle growth spray 8oz btl 7.95each 3.95s/h
   ask for(grow7)at lakeside products
   3038 nw25th av pompano beach FL 33069
   954-978-0597 9am-3pm EST

   From MrSoul
   Gibberellic Acid is available from these folks:
   Santa Barbara Science
   PO Box 41960
   Santa Barbara CA 93140-1960
   Item # 2859$4.00 + $5.00 S/H
   E-mail: science@west.net

   Posted by Firefly on March 18, 1998 at 14:54:13:

   www.plant_hormones.bbsrc.ac.uk/education/KenG.htm has a
   good info on gibberlins, also if you email me your email i will send you addys for
   about 5-6 more websites
   on various growth hormones.....

   I saw this source posted some time ago when I was considering picking it up, but I never followed up.
   Deer Creek Products, 8oz bottle is $8- + $4- S&H. The item # is "Grow 7" and they can be reached at
   (954)978-0597. Hope this helps. mp


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