Ga by John Riley
Hormones By Leo Write
Vic High's notes on using GA to induce self-pollination
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 (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.
The powder may be dissolved as specified below to give the desired concentration.
|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|
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
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
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.
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
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.
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
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 :
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....
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
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.....
HERB KIND, SORRY BUT THERE IS A - AND NOT A _ BETWEEN PLANT
AND HORMONES IN THAT ADDY I GAVE YOU, TOO MUCH OF A
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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