Introduction to Plant Growth Regulators and Growth Promoters

1. Indoleacetic Acid (IAA)

Physiological Actions: Prevents plant senescence, maintains apical dominance, promotes parthenocarpy, induces phototropism, and promotes cell elongation and bending.

Main Uses: Promotes rooting of cuttings; produces seedless fruit; promotes vegetative growth and reproduction, prevents flower and fruit drop, and increases yield; promotes seed germination; and induces callus and root formation in tissue culture.

2. Indolebutyric Acid (IBA)

Physiological Actions: Same as indoleacetic acid.

Main Uses: Similar to indoleacetic acid, but more effective than indoleacetic acid in promoting rooting of cuttings, inducing more numerous and slender adventitious roots. Combining indolebutyric acid with naphthaleneacetic acid yields even greater results.

3. Naphthaleneacetic Acid (NAA)

Physiological Actions: Shares the same characteristics and physiological functions as indoleacetic acid. It enters the plant through leaves, tender epidermis of branches, and seeds, and flows with nutrients to the affected areas throughout the plant. It enhances plant metabolism and photosynthesis, promotes cell division and expansion, and stimulates growth.

Main Uses: Improves stress resistance; induces adventitious root formation, promoting rooting of cuttings; promotes flowering and alters the male-female flower ratio; prevents flower drop and increases fruit set; thins flowers and fruits; promotes early maturity and increases yield.

IV. PCPA

Physiological effects: Similar to indoleacetic acid. When spraying PCPA, avoid young shoots and leaves to prevent phytotoxicity.

Main uses: Preventing flower and fruit drop; accelerating young fruit development; producing seedless fruit.

V. 2,4-D

Physiological effects: Depending on the dosage and concentration, 2,4-D produces a variety of plant effects. At low concentrations (0.5-1.0 mg/L), it is a common ingredient in tissue culture. At slightly higher concentrations (1-5 mg/L), it can prevent flower and fruit drop in fruits and vegetables and induce seedless fruit production, especially when night temperatures fall below 15°C. At even higher concentrations (1000 mg/L), it can control a variety of broadleaf weeds, with significant effects at temperatures between 20-25°C.

Main uses: Herbicide; preventing flower and fruit drop; inducing seedless fruit production; preventing pre-harvest fruit cracking; tissue culture.

6. Gibberellic Acid GA3

Physiological Effects: Promotes cell division and elongation; promotes protein and nucleic acid synthesis; promotes parthenocarpy; antagonistic to abscisic acid. The effective period of gibberellins varies depending on the crop type, but is generally about two weeks.

Main Uses: Breaks dormancy and promotes seed germination; promotes internode elongation and new shoot growth; prevents fruit drop and increases fruit set; promotes the formation of seedless fruit and early fruit ripening; prevents fruit cracking; inhibits flower bud differentiation.

7. 6-Benzylaminoadenine (6-BA)

Physiological Effects: Promotes cell division and induces tissue differentiation; relieves apical dominance and promotes lateral bud growth; induces chlorophyll formation and enhances photosynthesis; maintains cell membrane structural integrity and delays aging; accelerates plant metabolism and protein synthesis, thereby promoting rapid growth.

Main uses: Promote seed germination; induce dormant bud growth; promote the differentiation and formation of flower buds; prevent premature aging and fruit shedding; promote fruit enlargement; increase fruit setting rate; storage and preservation; tissue culture; improve plant disease resistance and cold resistance, etc.

8. Forchlorfenuron

Physiological Effects: Its activity is several dozen times that of 6-BA. It accelerates cell mitosis and promotes both longitudinal and lateral organ growth, thereby enlarging fruit. It also promotes chlorophyll synthesis, darkening and turning leaves greener, and enhancing photosynthesis. It also promotes protein synthesis.

Main Uses: Promotes fruit enlargement; delays leaf senescence and prevents leaf drop; induces bud differentiation, breaks apical dominance, promotes lateral bud germination and branch formation; prevents flower and fruit drop; increases sugar content, improves quality, and enhances marketability.

9. Brassinolide (BR)

Physiological Effects: Natural brassinolide is 1,000-10,000 times more active than auxins, enhancing enzyme activity in plants; promoting cell division and elongation; promoting vegetative and reproductive growth, improving fertilization capacity; and increasing photosynthesis.

Main Uses: Improves seed germination rate; increases fruit set rate; promotes fruit enlargement; increases yield; improves drought and cold tolerance; and enhances disease resistance.

10. Etychlozate

Physiological Effects: It is primarily absorbed through plant stems and leaves, then transported to the roots, promoting root physiological activity. It also promotes the release of ethylene, causing young fruit to drop, thus thinning fruit. It also alters fruit composition, improving fruit quality. Etychlozate should not be used on weak trees or in temperatures that are too high or too low. Re-spraying after application in the event of rain is not necessary to avoid phytotoxicity.

Main Uses: It replaces manual flower and fruit thinning, saving labor; increases sugar content; and promotes earlier fruit ripening.

Note: Plant growth regulators require high technical skills and strict concentration requirements. Consult with local technical personnel before use to minimize unnecessary losses.