Understanding the Gibberellin Family: GA₃ vs. GA₄+₇

Gibberellins are a large family of plant growth regulators comprising more than 130 naturally occurring compounds. They regulate key physiological processes, including seed germination, vegetative growth, flowering, and fruit set. Their discovery originated from research into rice bakanae disease. Today, GA₃ and GA₄+₇ are among the most widely used gibberellins in agriculture. This article compares their characteristics and field applications.

1. Origins: How Rice Bakanae Disease Led to the Discovery of Gibberellins

In the early twentieth century, Japanese rice fields experienced outbreaks of bakanae disease, characterized by excessive shoot elongation, thin stems, lodging, and poor grain set. In 1926, Eiichi Kurosawa demonstrated that a growth-promoting substance was responsible for these symptoms. In 1935, Teijiro Yabuta isolated crystalline gibberellin. During the 1950s, researchers determined the chemical structure of GA₃ and subsequently identified GA₄ and GA₇. Industrial fermentation production of GA₃ began in 1958, followed by wider use of GA₄+₇ for fruit retention in orchards.

Gibberellins are not exclusively synthetic, externally applied “artificial hormones”: higher plants naturally produce them. Fermentation-derived GA₃ and GA₄+7 have the same chemical structures as their endogenous counterparts and can be recognized and utilized by plants.

2. Basic Properties: Similarities and Key Differences

2.1 Shared Characteristics

Both are tetracyclic diterpenoid compounds and share the same basic mechanism of action: they bind to receptors in plant cells, activate gene expression, promote cell elongation and division, and interact with endogenous hormone systems.

• Safety: Plant and animal hormone receptor systems are fundamentally different, so gibberellins cannot act on the human body through the same hormonal mechanisms. Residues are very low when products are used in accordance with applicable requirements, allowing food safety risks to be controlled.

  
  

• Production: Both are produced through microbial fermentation, followed by extraction and purification, and formulated into products such as aqueous solutions, soluble powders, and emulsifiable concentrates.

2.2 How Structural Differences Affect Performance

Small differences in molecular structure contribute to different applications.

GA₃ (C₁₉H₂₂O₆) has stronger activity in promoting cell elongation but is less resistant to intense light, high temperatures, and alkaline conditions. Its effects generally last 7–10 days.

GA₄+₇, a mixture of GA₄ (C₁₉H₂₄O₅) and GA₇ (C₁₉H₂₂O₅), contains fewer hydroxyl groups and offers greater stability. It places greater emphasis on cell division, with effects lasting up to 15–20 days and a broader temperature range for application.

3. Comparing Physiological Functions, Crop Applications, and Use Requirements

3.1 Physiological Functions

Function	GA₃ — Gibberellic Acid	GA₄+₇ — A4+A7
Breaking dormancy	★★★★★ Strong activity; rapidly induces α-amylase and is suitable for deeply dormant seeds	★★★☆☆ Moderate activity; suitable only for seeds with shallow dormancy
Vegetative growth	★★★★★ Strong internode elongation; rapidly increases plant height	★★★☆☆ More moderate growth promotion, with less tendency toward excessive elongation
Flower and fruit retention	★★★★☆ Clearly improves fruit set; high concentrations may induce malformed fruit	★★★★★ Promotes consistent fruit set and uniform young fruit development, with fewer malformed fruit
Fruit enlargement and quality	★★★☆☆ Can increase fruit size but may reduce sugar content and firmness	★★★★★ Promotes uniform fruit enlargement and may improve sweetness, firmness, and coloration
Support under stress	★★☆☆ Lower stability; high temperatures may cause degradation and loss of activity	★★★★☆ Improves crop tolerance to cold and drought

3.2 Application Scenarios

✅ GA₃: Primarily for Rapid Growth Promotion

• Leafy vegetables — celery, spinach, and lettuce: Apply during the seedling stage to accelerate petiole elongation and bring harvest forward.

• Seed soaking for cereals — rice, wheat, and maize: Improve germination under low temperatures and promote uniform emergence and vigorous seedlings.

• Ornamental flowers — peonies and tulips: Break dormancy, encourage earlier flowering, and increase flower stem length.

✅ GA₄+₇: Primarily for Quality Improvement and Consistent Yield

• Fruit crops — apples, pears, and grapes: Apply after flowering during early fruit development to improve fruit retention, reduce malformed fruit, and enhance quality.

• Berries — strawberries and blueberries: Apply from flowering to early fruit development to promote uniform coloration.

• Protected fruiting vegetables — tomatoes and peppers: Reduce flower drop during cool flowering conditions and promote uniform fruit size.

3.3 Key Application Parameters

Parameter	GA₃	GA₄+₇	Application Notes
Spray concentration	20–100 mg/L; varies considerably by crop	10–30 mg/L	GA₃ has a narrower margin for concentration errors; excessive application can readily cause excessive elongation and malformed growth
Suitable temperature	20–25°C; more prone to degradation above 30°C	15–30°C; broader temperature adaptability	Evening application is preferred for GA₃
Tank mixing	Compatible only with neutral or mildly acidic formulations	Can be combined with most neutral or mildly alkaline products	Conduct a small-scale compatibility test before mixing; do not mix GA₃ with alkaline pesticides such as Bordeaux mixture
Duration of effect	7–10 days; repeated applications may be needed	15–20 days; fewer applications may be required	Choose GA₃ for short-term growth promotion and GA₄+7 for longer-term fruit quality improvement

4. Selection Principles and Common Misconceptions

Neither GA₃ nor GA₄+₇ is inherently superior. The appropriate choice depends on the intended result.

Selection Criteria

1. Regulation objective: Choose GA₃ for germination promotion and rapid vegetative growth; choose GA₄+₇ for fruit retention, fruit enlargement, quality improvement, and greater marketability.

2. Crop type: Prioritize GA₃ for leafy vegetables, cereals, and ornamental flowers; prioritize GA₄+₇ for fruit trees, berries, and high-value fruiting vegetables grown under protected cultivation.

3. Environmental conditions: Prioritize GA₄+₇ under high temperatures, intense light, or alkaline field conditions. Under moderate temperatures and neutral soil conditions, GA₃ offers better cost efficiency.

4. Growth stage: Use GA₃ to promote growth during the vegetative stage; GA₄+₇ is recommended during reproductive stages, including flowering, fruit set, and fruit enlargement.

Four Common Misconceptions

1. “GA₄+₇ works for everything.” Its growth-promoting effect on leafy vegetables is weaker than that of GA₃. Using it without a clear purpose may simply increase costs.

2. “A higher concentration gives better results.” Excessive application of either product can cause phytotoxicity. GA₃ may cause excessive elongation and malformed growth, while GA₄+₇ may cause leaf curling and fruit drop.

3. “Gibberellins alone can increase yield.” Gibberellins regulate growth signals and cannot replace nutrients. Inadequate water and nutrition may result in weak, excessive growth and reduced yield.

4. Confusing technical-grade purity with application concentration. Technical-grade active ingredient content cannot be used directly as the field spray concentration. Dilution must be calculated from the active ingredient content of the formulated product.

5. Industry Development Trends

As agriculture shifts toward more precise crop management and quality improvement, gibberellin products continue to evolve:

• GA₃: Microencapsulated, controlled-release formulations are a research direction aimed at improving stability and reducing application frequency.

• GA₄+₇: Combination products are mainstream, pairing GA₄+₇ with 6-BA or auxins to integrate flower retention and fruit enlargement.

• Production: Genetically engineered, high-yield microbial strains and greener extraction processes are improving fermentation efficiency and reducing environmental impact.

Conclusion

The progression from the discovery of gibberellins through rice bakanae disease to the widespread agricultural use of GA₃ and GA₄+7 illustrates how discoveries in nature can become practical tools for modern farming.

GA₃ is an effective tool for promoting seed germination and leafy vegetable growth, while GA₄+₇ is a preferred option for fruit retention and quality improvement in fruit trees and berries. Selecting the appropriate product according to crop objectives, growth stage, and environmental conditions, and providing adequate water and nutrition - helps realize the value of gibberellin regulation while reducing the risks of indiscriminate use.

As technology advances, gibberellins will continue to support more consistent yields and improved crop quality.

Understanding the Gibberellin Family: GA₃ vs. GA₄+₇