The Gibberellin Family Explained: A Scientific Comparison of GA₃ and GA₄+₇

In the field of plant growth regulation, gibberellins (GAs) form a vast “family” of natural compounds — with more than 130 distinct gibberellins identified to date. Acting as the plant’s internal “growth commanders,” these substances coordinate essential physiological processes such as seed germination, stem elongation, flowering, and fruit development.

Interestingly, the discovery of this family traces back to a puzzling rice disease that once troubled farmers, leading scientists on a decades-long journey of exploration and discovery.

Today, we focus on the two most widely used members of this family — GA₃ (Gibberellic Acid) and GA₄+₇ (Gibberellic Acids A₄ and A₇) — to uncover their distinct characteristics, scientific principles, and application differences.

I. Origins: From “Foolish Seedling Disease” to the Discovery of the Gibberellin Family 

The story of gibberellins began in early-20th-century Japan, where rice farmers noticed a strange phenomenon: some rice plants grew excessively tall with weak, thin stems that easily lodged and bore almost no grains. Farmers called it “bakanae disease,” or “foolish seedling disease.”

In 1926, Japanese plant pathologist Eiichi Kurosawa conducted the first systematic experiments on the disease. He ground up diseased rice stems, extracted their sap, and applied it to healthy plants — which then showed the same excessive elongation. The experiment proved that the pathogen produced a substance that could strongly stimulate plant growth. Kurosawa named it “gibberellin,” after the fungus Gibberella fujikuroi that caused the disease.

Over the following decades, scientists around the world continued to explore this mysterious compound. In 1935, Japanese researcher Teijiro Yabuta successfully crystallized the active substance from fungal cultures. By the 1950s, British scientists Brian Cross and J. MacMillan determined the molecular structure of GA₃, followed soon by the discovery of GA₄ and GA₇ in peas and maize. These three became the best-known natural representatives of the gibberellin family.

By 1958, GA₃ entered industrial production through microbial fermentation, and a few years later, GA₄+₇ gained wide use in fruit crops to regulate fruit set and development.

Importantly, gibberellins are not synthetic hormones. Nearly all higher plants — from wheat and maize to apples — naturally synthesize various types of gibberellins in actively growing tissues such as root tips, shoot tips, and immature seeds. Industrial GA₃ and GA₄+₇ are chemically identical to these natural forms and can be readily recognized and utilized by plants.

II. Fundamental Understanding: Core Characteristics of GA₃ and GA₄+₇

As key members of the gibberellin family, GA₃ and GA₄+₇ share many similarities but also exhibit distinct differences. Understanding their core attributes is the foundation for applying them correctly.

2.1 Common Traits — The Core Power of Growth Regulation

Chemically, both GA₃ and GA₄+₇ are tetracyclic diterpenoid compounds with the characteristic gibberellin skeleton. This shared structure underlies their similar physiological functions.

Their mode of action is essentially the same: both bind to specific receptor proteins (GID1) within plant cells, triggering the degradation of DELLA proteins that normally inhibit growth. This activation promotes cell elongation (by loosening cell walls and enhancing vacuole expansion) and cell division, while balancing the levels of other hormones such as abscisic acid and auxin.

In terms of safety, both follow the same scientific logic — plant hormones differ fundamentally from animal hormones in structure and receptor systems. GA₃ and GA₄+₇ cannot bind to human receptors and have no cross-species biological activity. Once ingested, they are broken down by the digestive system into simple organic molecules. When used according to regulations, their residues in crops are well below established safety limits, posing no food safety risk.

For production, both GA₃ and GA₄+₇ are manufactured via microbial fermentation, using specific strains of Gibberella fujikuroi in carefully controlled bioreactors. Parameters such as temperature, pH, and aeration are precisely regulated to optimize synthesis. The fermentation broth is then extracted and purified to yield high-purity active ingredients, which are formulated into emulsifiable concentrates, water solutions, or soluble powders for agricultural use.

2.2 The Root of Their Differences — Structure Determines Behavior

The fundamental difference between GA₃ and GA₄+₇ lies in their molecular structure.

• GA₃ has the molecular formula C₁₉H₂₂O₆, featuring a distinctive lactone ring and several hydroxyl groups.

• GA₄ (C₁₉H₂₄O₅) and GA₇ (C₁₉H₂₂O₅) contain fewer hydroxyl groups, giving them slightly greater structural stability.

This small structural variation leads to clear differences in stability, biological activity, and application performance.

Stability: GA₃ is more sensitive to light, heat, and alkaline conditions, degrading faster above 30 °C or at pH > 7.0, with an effective duration of about 7–10 days. GA₄+₇ shows slightly better stability under light and alkaline environments, extending its effectiveness to roughly 15–20 days.

Activity focus: GA₄+₇ generally exhibits higher biological activity in cell division and fruit development, while GA₃ is slightly stronger in promoting cell elongation. This difference defines their respective application domains.

III. Comparative Applications: GA₃ vs. GA₄+₇ Across Crops and Functions

Because of their distinct structural and physiological characteristics, GA₃ and GA₄+₇ show clear boundaries in use — each excelling in specific crops and growth stages.

3.1 Key Physiological Functions

Function	GA₃ (Gibberellic Acid)	GA₄+₇ (Gibberellic Acids A₄+A₇)	Core Reason
Breaking seed dormancy	★★★★★ Very strong; rapidly activates α-amylase synthesis, effective for hard-to-germinate seeds	★★★☆☆ Moderate; effective mainly on lightly dormant seeds	GA₃ directly enhances α-amylase production
Vegetative growth	★★★★★ Strong elongation of stems and petioles	★★★☆☆ Milder; less risk of excessive elongation	GA₃ promotes elongation; GA₄+₇ favors division
Flower and fruit retention	★★★★☆ Improves fruit set but high doses may cause deformities	★★★★★ Stable fruit set, uniform development, fewer deformities	GA₄+₇ provides balanced stimulation of reproductive organs
Fruit enlargement & quality	★★★☆☆ Enlarges fruit but may reduce sweetness and firmness	★★★★★ Promotes uniform growth, improves sweetness, firmness, and coloration	GA₄+₇ supports sugar accumulation; GA₃ may unbalance nutrient flow
Stress resistance	★★☆☆☆ Weaker and unstable at high temperature	★★★★☆ Enhances cold and drought tolerance	GA₄+₇’s structure maintains activity under stress

3.2 Crop and Application Scenarios

GA₃ — for rapid growth control:

• Leafy vegetables: Celery, spinach, lettuce — spraying appropriate concentrations during vigorous growth promotes elongation of petioles and leaves, advancing harvest by 5–7 days.

  
  

• Seed treatment for cereals: Soaking rice, wheat, or maize seeds in GA₃ solution before sowing enhances germination in cool conditions and promotes uniform seedling emergence — a common practice in cold regions.

  
  

• Ornamental forcing: In bulbous flowers such as peony and tulip, GA₃ breaks dormancy and induces earlier flowering with longer stalks and improved display value.

  
  

GA₄+₇ — for quality improvement:

• Fruit trees: Apples, pears, and grapes respond well to GA₄+₇ sprays about 1–2 weeks after full bloom (early fruit stage), improving fruit set and reducing deformity while enhancing firmness and sweetness.

  
  

• Berries: Strawberries and blueberries show better color uniformity and surface gloss when treated during flowering or early fruit stages.

  
  

• Protected vegetables: Tomatoes and peppers benefit from GA₄+₇ applications in cool seasons to prevent flower drop, improve fruit set, and ensure uniform fruit size.

  
  

3.3 Key Usage Parameters

Parameter	GA₃	GA₄+₇	Recommendation
Effective concentration	20–100 mg/L (varying by crop)	10–30 mg/L	Adjust GA₃ strictly by crop type; excessive use causes elongation or deformity. Too-high GA₄+₇ levels may curl leaves.
Optimal temperature	20–25 °C (degrades above 30 °C)	15–30 °C (wider range)	Spray GA₃ preferably in the evening; GA₄+₇ can be applied throughout the day, avoiding intense midday light.
Tank-mix compatibility	Compatible only with neutral or weakly acidic materials	Compatible with most neutral or slightly alkaline products	Avoid mixing GA₃ with strongly alkaline pesticides (e.g., Bordeaux mixture); always conduct small-scale tests with GA₄+₇.
Duration of effect	7–10 days	15–20 days	GA₃ for short-term vegetative boost; GA₄+₇ for long-term reproductive regulation.

IV. Scientific Selection: Matching the Right Gibberellin to the Right Need

GA₃ and GA₄+₇ are not “better or worse,” but fit for different purposes. Scientific selection depends on crop type, growth stage, and the desired regulatory outcome.

4.1 Core Selection Principles

• By target: For rapid elongation or germination — choose GA₃; for fruit quality and stability — choose GA₄+₇.

  
  

• By crop type: Leafy vegetables, cereal seeds, and ornamentals suit GA₃; fruit trees, berries, and greenhouse crops benefit more from GA₄+₇.

  
  

• By environment: In hot, high-light, or alkaline soils, GA₄+₇’s greater stability ensures reliability; under neutral, moderate conditions, GA₃ offers higher cost-effectiveness.

  
  

• By growth stage: Use GA₃ during vegetative stages (seedling, elongation); use GA₄+₇ during reproductive stages (flowering, fruit set, expansion).

  
  

4.2 Common Misunderstandings

1. “GA₄+₇ is always superior.” In crops like celery or spinach, GA₃ remains irreplaceable for elongation. GA₄+₇ is not a universal substitute.

   
   

2. “Higher concentration means better results.” Excessive doses of either cause phytotoxicity — GA₃ may induce lodging or deformities, GA₄+₇ may curl leaves or cause fruit drop.

   
   

3. “Gibberellins replace fertilization.” They regulate growth signals, not provide nutrition. Without proper soil fertility and N-P-K balance, overreliance can cause weak, low-quality growth.

   
   

4. “Confusing raw material with formulation.” Application concentrations must be calculated based on the active ingredient percentage in the formulation (e.g., 10 % soluble powder), not the pure active compound.

V. Industry Trends: Innovation and Standardization in Gibberellin Products

As modern agriculture moves toward precision and quality, both GA₃ and GA₄+₇ are evolving in technology and application.

• Product innovation: GA₃ research focuses on enhancing stability — for example, microencapsulation technologies for slow-release formulations to extend duration and reduce spray frequency. GA₄+₇ development emphasizes combination products with auxins (e.g., 2,4-D) or cytokinins (e.g., 6-BA) for integrated “fruit-set + fruit-growth + quality improvement” solutions.

  
  

• Manufacturing upgrades: Green bioprocessing is now mainstream. Through genetic optimization of Gibberella fujikuroi strains, fermentation yield has increased by about 15–25 % compared with conventional strains. Environmentally friendly extraction solvents further reduce chemical waste and pollution.

  
  

Together, these innovations mark the shift of gibberellin products toward higher efficiency, environmental sustainability, and precise application.

VI. Conclusion: Choosing the Right “Commander” for Smarter Growth

From a mysterious factor behind rice “foolish seedling disease” to widely used tools in modern agriculture, gibberellins embody the spirit of discovering solutions from nature.

GA₃, with its strong elongation power, serves as a key tool for boosting leafy vegetable yield and seed germination. GA₄+₇, with its balanced activity and stability, has become a premium regulator for enhancing fruit quality and productivity.

The essence of using gibberellins lies in understanding the crop’s true needs — selecting the right type, timing, and conditions to achieve precise control rather than blind stimulation.

As innovation and standardization continue, GA₃ and GA₄+₇ will play an increasingly vital role in improving agricultural efficiency, ensuring food security, and raising the quality of produce worldwide.