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Using Plant Hormones

Plant hormones are natural chemicals produced in minute quantities in one part of a plant and have a physiological effect when moved to another part of the plant; a chemical messenger. Hormones control growth or other physiological functions such as root initiation, flowering, fruit drop, etc. Unlike animal hormones, phytohormones are not produced in individual organs, but are produced by every cell at various times during a plant’s growth cycle. They are necessary for communication in plants because plants do not contain nervous systems. Naturally-produced hormones are properly called hormones or phytohormones. There are three major groups of plant hormones:

a) Auxins

Auxins are plant hormones that influence cell enlargement, root initiation, and bud formation. They suppress the initiation of lateral buds.

These messengers cause cells to elongate. When cells elongate on one side of a plant only, they cause the plant to bend. The elongation is irreversible and widely used in horticulture and agriculture. Perhaps one of the most familiar uses is in the elongation of green grapes, which provide growers with more fruit substance per bunch.

The common rooting hormones available in most garden stores all contain auxins in minute concentrations. Auxins, usually indole-butric acid, are formed naturally in fruits, seeds, pollen, growing points, young leaves and developing buds. Auxins cause cells to grow and especially to elongate & auxins promote apical dominance.

Keikiroot with a minute concentration of the auxin has been found advantageous for orchid root initiation and development.

b) Cytokinins

Cytokinins are plant hormones that are involved in cell division, shoot multiplication and axillary bud proliferation (buds developing in the leaf axils). They help delay senescence (aging). If plants are too spindly, increased cytokinin will help foster shorter, thicker stems.

Rather than affect cell growth, such as elongation or inhibiting dormancy, cytokinins promote the change in a standard plant cell to a cell that becomes a stem, a root, a leaf or a flower.

It is this group of hormones that is of special interest to orchid growers. Cytokinins cause cells to differentiate into stems, leaves and eventually flowers.

Cytokinins suppress this tendency of plants to reach for the light.

c) Gibberelic Acid or Gibberellins

Gibberellins are a group of naturally occurring substances that influence cell enlargement and stem elongation. Gibberellins also supplement the actions of auxins and cytokinins.

These hormones are isolated from many different plants, but primarily fungi and are used to increase the growth of many plants and seedlings because they function like plant hormones in stimulating the growth of roots, leaves and stems, the germination of seeds, etc. Now over fifty gibberellins have been isolated and are used commercially, primarily for stem elongation and seed germination. They have been used to induce flowering by breaking dormancy and they can be used to offset a plant’s requirements of long day exposure or periods of low temperature in order for it to flower.

d) Minor Groups of Hormones / Plant Regulators

There are now many compounds, including enzymes which have been isolated and identified. Little experimental data is available about them and certainly little experimentation has been conducted on orchids. A few have achieved a status where more experimentation should be attempted. A few examples may illustrate their effects on plant growth.

Florigens: These are thought to stimulate the flowering of plants. They are now usually referred to as anthesins. Dormins: These compounds are thought to inhibit growth. Perhaps they have use in producing miniature plants for light culture. Ethylene: This is probably the best known member of this minor category because it has many uses including many not related to plant growth. It is a colorless, flammable, gaseous hydrocarbon obtained from petroleum and as a plant regulator it is useful for the ripening of fruits. Green bananas, for example, are sprayed by the shipload so that they ripen by the time the ship arrives at its destination. Many tropical gardeners will be familiar with the “trick” of getting bromeliads to bloom by confining the plant in a plastic bag with a well- ripened apple. The apple, as it ripens produces ethylene and the bromeliad “ripens” or produces a flower.

  • APICAL DOMINANCE

    A constant flow of auxins from the apical (top) buds in a plant suppress dormant buds further down the plant. This action gives a plant it’s shape by only allowing the top buds to grow. Apical dominance controlled by a constant flow of auxins allows plants to have an important survival mechanism when a plant is damaged. When the top of a gum tree for example, is burnt in a fire or broken off during a storm, the loss of the auxin flow from the growing tip of the tree causes the buds at the base of every stem to grow and a tree with shoots all up the trunk results. The most advanced of these new branches will replace the damaged ones and eventually start to produce auxins to themselves to re-establish apical dominance in the tree.

    By adding cytokinins to the buds at the base of virtually any plant, we are able to produce stems, leaves, branching and eventually flowers without damaging the plant. This same effect can also cause axillary buds on plants such as those on the stems of African violets to go into growth, rather than remain dormant.

    By altering the balance of auxins and cytokinins in a plant we are able to overcome the dominating effect of the tip of the plant in a very selective way.

    This is an over-simplification, but it provides the basis for the production of keikis (plantlets) on Phalaenopsis or the activation of a dormant bud in orchids when the major lead or the tip of a plant has been damaged or we want to proliferate the growths. Many orchids have had to survive hurricanes and floods during which their major growths have been damaged. We can take advantage of this self-preserving mechanism in an orchid by applying plant growth regulators and, without damaging the plant, increase its production or promote its survival capabilities.

  • USE OF PLANT HORMONES

    When plant hormones are used by growers to change the way their plants grow they are more correctly called growth regulators. Here are some examples of what we can do using growth regulators.

    1. Keiki Production on Phalaenopsis Orchid Flower Spikes

    The propagation of Phalaenopsis keikis is the easiest application for the use of plant hormones, because the defense mechanism of the plant is most easily accessible. Keikis, a Hawaiian word for baby plants, are frequently produced by Phalaenopsis in the wild (in situ) because of the natural hormones present in the plant itself The application of Keikigrow Plus (a mixture of the cytokinin BAP and vitamins in a lanoline paste) can merely assist the plant’s natural inclination to produce cytokinins and perpetuate itself by prompting dormant reserve buds into growth.

    To summarize, we can promote keikis without damaging the plant by simply enhancing the hormonal content of the meristem tissue which is already poised to affect differentiation, but which is restrained by the phenomena of apical dominance.

    Carefully slit the bract covering the second node from the bottom of the inflorescence. The bottom node seldom produces a keiki. Be careful not to damage the bud beneath the bract. Depending on the age of the plant one or two additional buds may be treated on the spike.
    Don’t be greedy and try to develop too many keikis. A large mature Phalaenopsis might support many keikis, but a first bloom seedling should be treated with care. Do not treat the fifth bud counting from the base of the inflorescence. It generally produces a branch to the flower spike.
    Carefully remove the bract.
    Do not apply the regulator until after the last flower on the Phalaenopsis flower spike has opened fully. This timing is crucial and not a casually “recommended” procedure.

    The purpose of the application is to bolster the natural hormones of the plant and these naturally occurring substances will not be produced until the plant enters its growth cycle after blooming has occurred.

    Waiting several weeks on a younger plant would raise the probability of success.
    Apply a small amount (the size of a green pea, is ample) of the plant growth regulator, Keikigrow Plus, to the bud and the surrounding tissue. This cytokinin is suspended in lanolin (oil removed from sheep wool). Small amounts of Vitamin B-i and Vitamin B-2 are included in the formula so that any resulting growth has a positive cultural milieu similar to what would be included in a flasking procedure. The importance of the lanolin is that it sheds moisture, may be massaged into the plant tissue and will not wash off during normal watering or the generally high humid atmosphere of an orchid-growing greenhouse or light-growing area.

    Nutrition

    Since the application to the flower stem is after the Phalaenopsis has flowered and is beginning to enter the vegetative cycle of its growth, it is generally acceptable to provide extra nitrogen for support of green growth.

    In one or two weeks the tiny bud should show signs of development. The time of development varies greatly because of growing conditions of the plant, genetics and a host of other variables.

    The speed of development depends on many characteristics of both the plant and the cultural conditions in which it is being grown. The following conditions have been found conducive to speedy and healthy keiki growth and development:
    1) Maintaining a daytime temperature of at least 22 degrees C.
    2) Treating only nodes 2, 3, 4 counting up from the base of the inflorescence.
    3) Maintaining at least 60% relative humidity.
    4) Using fertilizer of 30-10-10 or 6-i-i (NKP) during the period when you expect keikis to develop.
    20] When the keiki has about four roots, two centimeters long, it can be removed. Root development usually follows leaf differentiation. Occasionally roots will develop first. It is not necessary to cut the keiki. A brisk twist will usually cause the keiki to separate naturally. The small scar may be protected with a fungicide such as powdered sulphur, but it usually washes off during misting or watering. Stoprot (with bordeaux mix in lanolin) is an excellent fungicide and a sealant. Adding Vitagrow B-i to your regular fertilizer improves root development. Roots may be initiated by the application of lanolin-based Keikiroot.

    2. Producing Extra Flower Spikes

    This can be achieved by applying Keikigrow Plus or better still Floral Boost which is a mixture of cytokinin hormones and vitamins in lanolin specifically designed to produce extra flower spikes.

    The regulator can be applied before flowering to two or three nodes on the upper portion of the spike, immediately below the lowest flower bud to promote spike branching.

    After flowering the hormone paste is applied to one of the upper-most buds on the spent spike to encourage secondary flowering. Some Phalaenopsis do not branch at all and the regulator can be used to promote branching.

    This technique will also work with the spikes of some Oncidiums, particularly the equitants and can be applied to the base of lower leaves on Angraecoids, Vandas and Ascocendas.

    3. Rescuing Damaged Plants

    One of the most important side-benefits of applying Keikigrow Plus is the encouragement of adventitious buds in the attempt to save damaged plants. Buds that are slightly swollen are poised to go into growth and may be encouraged by Keikigrow Plus.
    This technique has been used to rescue crown-damaged Phalaenopsis and other monopodial orchids. The Keikigrow Plus is applied to buds around the base of the plant (not to the inflorescence). There is a dormant bud at the base of every leaf. Some will be dry, but others will be green and ready for extra encouragement to send them into growth.
    A healthy root system can support these dormant buds to grow even when the primary growth is damaged.

    Adventitious buds on the stem of a crown-damaged Phalaenopsis frequently respond to the application of plant regulators because the root development is active and supportive for a plant attempting to survive fungal, bacterial or animal damage.

    Crown-damaged Paphiopedilums and Phragmipediums also respond to the encouragement provided by Keikigrow Plus or better still Paph Grow because the damaged crown has caused the adventitious buds to expand in order to save the mother plant.

    4. Obtaining Plants from Cut Flower or Broken-Off Spikes

    Phalaenopsis cut flower spikes can be treated with Keikigrow Plus after the flowers have faded to produce keikis on the bare spikes. The spikes must be kept in clean water which is regularly changed to maintain it clean and the end of the spikes recut every few days to keep water flowing into the stem. Only treat one or two buds because the isolated stems have a very limited capacity to supply nutrients to the developing buds. If you see some beautiful Phalaenopsis flowers stems for sale you can now obtain a keiki from the spike to get your own plant of this flower. This is also a great way obtain a replacement plant when your original one dies while flowering.

    5. Obtaining Extra Plants from Old Canes or Bulbs

    Usually discarded dormant bulbs (back bulbs) can be encouraged to produce new growths after the application of plant regulators (Keikigrow Plus). New growths can be produced from old shriveled back bulbs. This is useful for plants such as species Cymbidiums and Dendrobium speciosum where some good clones are very reluctant to produce new growths. Buds at both the top and base of Dendrobium canes can be rubbed with Keikigrow Plus. The top buds generally responded with numerous keikis or sometimes extra flower spikes while buds at the base of the canes form shoots which then develop into new growths.

    The same technique also works for Cattleyas, Oncidiums and many other genera with dormant buds. Catasetum keikis from application to dormant buds on pseudobulb rings help increase these valuable plants for trading with friends or maintaining your own insurance plants in case of damage to your mother plant.

  • PLANTS OTHER THAN ORCHIDS

    Keikigrow plus can also be used on plants other than orchids. The caudex, (Diascorea or Testudinaria elephanties, of the yam family) rare in hobby greenhouses, is normally dormant for as long as 6 months. The application of plant hormones can induce a return to growth.

    The carnivorous pitcher plants the Nepenthes have a notorious reputation for reproduction. They must be trained to develop from the basil growths so that copious pitchers result. Fertilizer discourages pitchers, but the vine-like growth habit has to be curtailed in order for large pitchers to be produced. The plant regulator encourages basal growth, and therefore pitcher growth. Undeveloped buds may be encouraged at every leaf joint for the development of future cuttings and the multiple plants which produce many pitchers. These delightful Nepenthes are excellent companions to orchids and develop symetrical growth patterns when cut close to the base and rubbed with Keikigrow Plus.

    Bonsai growers have found hormonal growth regulators helpful in encouraging new branches where only adventious buds existed before. Valuable African violet chimeras can only be propagated from adventitious buds on flower stems. The ordinary method of African violet propagation will not reproduce the exotic chimeras. This cloning results in very valuable African Violets.