🧪 Growth Regulators in Horticulture
Growth Regulators in Horticulture.
Plant growth regulators are low-dose biochemical tools used in horticulture to manage rooting, flowering, fruit set, ripening, and shelf life with greater precision.
Classification of Plant Growth Regulators
Natural Plant Hormones
| Hormone | Primary Function |
|---|---|
| Auxins (IAA) | Cell elongation, apical dominance, rooting |
| Gibberellins (GA3) | Stem elongation, seed germination, flowering |
| Cytokinins (BAP, Kinetin) | Cell division, delayed senescence, shoot growth |
| Abscisic acid (ABA) | Dormancy, stomatal closure, stress response |
| Ethylene | Fruit ripening, senescence, abscission |
Synthetic Growth Regulators
- IBA: Root promotion in cuttings and layers
- NAA: Fruit retention, thinning, rooting support
- 2,4-D: Weed control and fruit drop management in selected uses
- CCC (Chlormequat): Growth retardant
- Paclobutrazol: Growth retardant and flowering promoter in mango
- Ethephon (Ethrel): Ethylene-releasing ripening regulator
Applications in Horticulture
Rooting of Cuttings
- IBA at 1000-3000 ppm promotes adventitious roots.
- NAA at 500-1000 ppm can be used as an alternative.
- Application forms: powder, quick dip liquid, or paste.
Flowering Regulation
| Crop | PGR | Concentration | Effect |
|---|---|---|---|
| Mango | Paclobutrazol | 2.5-5 ml/m canopy | Early and profuse flowering |
| Pineapple | Ethephon | 50 ppm | Uniform flowering |
| Chrysanthemum | GA3 | 100-200 ppm | Stem elongation |
| Litchi | Ethephon | 200 ppm | Increased female flowering tendency |
Fruit Set and Development
- NAA at 20 ppm or GA3 at 10-20 ppm can improve fruit set in mango.
- GA3 at 25-50 ppm can induce seedless berries in grape.
- PCPA supports tomato fruit set under high temperature.
Fruit Thinning and Ripening
- NAA at 10-20 ppm is used for thinning fruitlets in apple.
- Carbaryl at 600 ppm is used as a chemical thinner in some systems.
- Ethephon at 500-1000 ppm promotes ripening in banana, mango, and tomato.
Delaying Senescence
- GA3 and cytokinins delay yellowing in leafy produce and flowers.
- Silver thiosulphate (STS) extends vase life by suppressing ethylene action.
Summary Cheat Sheet
| PGR Group | Main Use |
|---|---|
| Auxins (IAA/IBA/NAA) | Rooting, fruit set adjustment |
| Gibberellins (GA3) | Stem elongation, fruit development |
| Cytokinins | Cell division, delayed senescence |
| ABA | Stress and dormancy responses |
| Ethylene/Ethephon | Ripening and abscission control |
References
2 sources • [1] [2]
References
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