What does "hormone orchid seedling" mean? A detailed guide in one article

First, avoid buying hormone-treated orchids. Generally, orchid seedlings grown in greenhouses are treated with hormones, while naturally cultivated orchid nurseries use them relatively less.

Simply put, plant growth regulators, that is, hormones. The issue of hormones is a sensitive topic, and most orchid enthusiasts turn pale at the mere mention of it. A hormone seedling is figuratively like a person who has been given stimulants, stimulating their life potential, such as producing more flowers and more shoots, so orchid enthusiasts will understand a bit better.

The following is quoted: Hormones are a type of pesticide, but they have a certain relationship with fertilizers. The growth and development process of plants is affected by external environmental conditions such as water, sunlight, potting medium, temperature, etc., and controlled by internal genetic factors, while what regulates and controls plant growth activities are certain metabolic substances, namely plant hormones. Plant hormones are endogenous active substances produced by the plant body, and they can be transported from the organs responsible for synthesis and this tissue to other organs or tissues. At present, the widely recognized plant hormones mainly fall into five major categories: auxins, gibberellins, cytokinins, abscisic acid and ethylene. In addition, scientists have also discovered other plant hormones such as brassinosteroids, salicylic acid, jasmonic acid, etc.

The functions of the five major categories of plant hormones:

I. Physiological effects of auxins

① Promote growth, but inhibit growth at high concentrations;

② Promote the formation of adventitious roots in cuttings, such as the main component of rooting agents being naphthaleneacetic acid;

③ Have a regulatory and transport effect on nutrients, and can induce seedless fruit;

④ Other physiological effects such as: causing apical dominance, promoting pineapple flowering, inducing female flower differentiation, etc.

II. Physiological effects of gibberellins

1. Promote stem elongation growth,

2. Induce flowering

3. Break dormancy

4. Promote male flower differentiation; GA treatment causes monoecious plants with separate male and female flowers to produce more male flowers

5. Induce parthenocarpy, etc.

III. Physiological effects of cytokinins

1. Promote cell division, mainly acting on cytoplasm division

2. Promote bud differentiation

3. Promote cell enlargement

4. Promote lateral bud development, eliminating apical dominance

5. Delay organ senescence; can be used to treat fruits and fresh flowers, etc., to keep them fresh and green, and prevent fruit drop;

6. Break seed dormancy; can replace light to break the dormancy of light-requiring seeds.

IV. Physiological effects of abscisic acid

1. Promote dormancy;

2. Promote stomatal closure

3. Inhibit growth; this inhibitory effect is reversible;

    4. Promote abscission;

5. Increase stress resistance; ABA is known as the stress hormone

V. Physiological effects of ethylene

1. Change growth habits, causing plants to exhibit the characteristic triple response and epinasty;

2. Promote ripening; it is known as the ripening hormone

3. Promote abscission; it is the main hormone controlling leaf abscission;

4. Promote flowering and female flower differentiation;

5. Induce the formation of adventitious roots in cuttings, break the dormancy of seeds and buds, and induce the secretion of secondary metabolites.

Since the discovery of plant hormones, people have wanted to use them in agricultural production. However, the content of hormones naturally present in plants is extremely low, so scientists use other methods such as microbial fermentation to concentrate and extract them, or use chemical methods to synthesize them by imitating the chemical structure of plant hormones. Such artificially synthesized and artificially extracted physiologically active substances are called plant growth regulators. Now I will briefly introduce the types of plant growth regulators on the market:

I. Auxin category:

1. Indoleacetic acid, mainly used to promote rooting. It promotes cell growth and cell differentiation, etc.

2. 2,4-D, which has auxin effects, promoting at low concentrations and inhibiting at high concentrations.

3. Naphthaleneacetic acid, whose main effects are promoting cell growth and promoting rooting.

4. Atonik, which is a sodium salt of nitrophenol compounds, has an obvious promoting effect on plant growth and development, rooting, flowering, and fruiting. If used at too high a level, it inhibits the growth of young plant buds.

II. Gibberellin category

Gibberellin is also called 920, and it mainly promotes cell growth, breaks dormancy, and promotes early flowering in plants.

III. Cytokinin category:

1. 6-Benzylaminopurine, abbreviated as 6-BA, has relatively high cytokinin activity. It is often used in tissue culture. It breaks apical dominance and promotes lateral bud growth.

2. Kinetin, 6-furfurylaminopurine, promotes cell division and tissue differentiation and delays the degradation of protein and chlorophyll.

IV. Plant growth retardant and inhibitor category:

1. B9, also called daminozide, mainly inhibits the transport of auxin in the plant body and the biosynthesis of gibberellins, delays vegetative growth, and makes leaves dark green, small and thick.

2. Triadimefon, a low-toxicity fungicide, can thicken leaves, reduce leaf area, and delay the growth of some parts of the pot surface.

3. Abscisic acid, promotes plant senescence and inhibits the physiological processes regulated by endogenous plant hormones (auxins, gibberellins, cytokinins).

Of course there are many more, and I will not list them one by one here!

Regarding the application of plant growth regulators, orchid enthusiasts more or less use them too. Everything has pros and cons. After use, there are many new shoots and rapid growth. But the resistance of orchids also declines rapidly, making them prone to collapse or the new shoots weak. The so-called orchid-specific bud and root stimulants sold on the market now more or less contain certain plant growth regulators, only most orchid enthusiasts do not know it. Naturally cultivated orchids have good stress resistance, and their ability to resist pests and diseases is better than those treated with plant growth regulators. Another point is that the concentration of plant growth regulators is not easy to master, because the dosage of plant growth regulators is especially small, sometimes one part per million, and it is generally not easy to master. If the concentration is high, it is likely to have the opposite effect. For example, if the concentration of gibberellin is too high, it easily causes orchid new shoots to grow wildly, and the consequence is lodging. Leaves become thinner, and seedlings easily collapse. If the concentration of 2,4-D is too high, it will inhibit growth or even kill the plant, and so on. Therefore, plant growth regulators should be used sparingly or not at all when growing orchids.

    (The hormone used for dwarfing orchids is daminozide (B9). It can be applied together with watering when the potting soil needs water. Spray once every 7 to 10 days with a 0.2% daminozide solution until both sides of the leaves are wet. It can effectively control plant height, making growth short and sturdy, and flowers large and brightly colored.)

Appendix: Table of uses of plant growth regulators

Plant growth regulators have a wide variety of uses. It can be said that from seed germination, rooting, leaf growth to flowering and fruiting, then seed formation, as well as postharvest fresh-keeping of fruits and vegetables and seed storage, growth regulators can all be used for regulation. The following lists various uses and the applicable names of plant growth regulators.

Use Applicable plant growth regulator names

Extend dormancy of storage organs Maleic hydrazide, sodium naphthaleneacetate, methyl naphthaleneacetate.

Break dormancy and promote germination Gibberellin, kinetin, thiourea, chloroethanol, hydrogen peroxide.

Promote stem and leaf growth Gibberellin, 6-benzylaminopurine, brassinosteroid, triacontanol.

Promote rooting Indolebutyric acid, naphthaleneacetic acid, 2,4-D, daminozide, paclobutrazol, ethephon, 6-benzylaminopurine.

Inhibit the growth of stems, leaves and buds Paclobutrazol, uniconazole, chlormequat, daminozide, pix, triiodobenzoic acid, maleic hydrazide, fenarimol.

Promote flower bud formation Ethephon, daminozide, 6-benzylaminopurine, naphthaleneacetic acid, 2,4-D, chlormequat.

Inhibit flower bud formation Gibberellin, fosamine.

Thin flowers and fruits Naphthaleneacetic acid, carbaryl, ethephon, gibberellin, indole ester, 6-benzylaminopurine.

Preserve flowers and fruits 2,4-D, naphthaleneacetic acid, 4-CPA, gibberellin, chlormequat, daminozide, 6-benzylaminopurine.

Extend flowering period Paclobutrazol, chlormequat, ethephon, daminozide.

Induce female flower formation Ethephon, naphthaleneacetic acid, indoleacetic acid, chlormequat.

Induce male flower formation Gibberellin

Fresh-keeping of cut flowers Aminoethoxyvinylglycine, aminooxyacetic acid, silver nitrate, silver thiosulfate.

Form seedless fruit Gibberellin, 2,4-D, 4-CPA, naphthaleneacetic acid, 6-benzylaminopurine.

Promote fruit ripening Ethephon, daminozide.

Delay fruit ripening 2,4-D, gibberellin, daminozide, kinetin, naphthaleneacetic acid, 6-benzylaminopurine.

Delay senescence 6-Benzylaminopurine, gibberellin, 2,4-D, kinetin.

Increase amino acid content Paclobutrazol, 4-CPA, indole ester.

Increase protein content 4-CPA, simazine, atrazine, naphthaleneacetic acid.

Increase sugar content Glyphosine, fosamine, pix.

Promote fruit coloring Daminozide, indole ester, paclobutrazol.

Increase fat content Naphthaleneacetic acid, maleic hydrazide, morphactin.

Improve stress resistance Abscisic acid, paclobutrazol, daminozide, chlormequat.