GIBBERELLIC ACID GA₃/ THE POWERFUL PLANT GROWTH REGULATOR(PGR)

Gibberellic acid (GA₃) is one of the most extensively studied and commercially important plant growth regulators (PGRs). It belongs to the gibberellin (GA) family, a group of naturally occurring diterpenoid plant hormones responsible for regulating numerous physiological and developmental processes. More than 130 different gibberellins have been identified in plants, fungi, and bacteria, but only a few—such as GA₁, GA₃, GA₄, and GA₇—are biologically active.

GA₃ was first isolated from the fungus Gibberella fujikuroi, the causal organism of the "Bakanae" (foolish seedling) disease in rice. Infected rice seedlings exhibit excessive elongation due to the overproduction of gibberellins.

MAJOR  SITES OF SYNTHESIS INCLUDE

• Young leaves
• Shoot apical meristems
• Developing seeds
• Embryos
• Fruits
• Root tips

MECHANISM OF ACTION

GA₃ functions by regulating gene expression involved in cell expansion and developmental growth.

Signal Transduction

1. GA₃ enters plant cells.
2. It binds to the GID1 receptor.
3. The GA–GID1 complex interacts with DELLA proteins, which normally suppress growth.
4. DELLA proteins are tagged for degradation through the ubiquitin-proteasome pathway.
5. Growth-promoting genes become active.
6. Cell division, cell elongation, and enzyme synthesis increase.

This mechanism explains why GA₃ promotes rapid stem elongation and vigorous vegetative growth.

PHYSIOLOGICAL ROLES

1. Stem Elongation

GA₃ stimulates:

• Cell elongation
• Cell division
• Cell wall loosening
• Expansion of internodes

This leads to taller plants with increased shoot growth.

2. Seed Germination

One of the most important roles of GA₃ is breaking seed dormancy

3. Breaking Dormancy

GA₃ helps overcome:

• Seed dormancy
• Bud dormancy
• Tuber dormancy

It is widely used in horticulture for improving germination of difficult-to-sprout seeds.

4. Flowering

GA₃ promotes flowering in:

• Long-day plants
• Biennial crops
• Some ornamental species

It can substitute for cold treatment (vernalization) in certain plants.

5. Fruit Development

GA₃ promotes:

• Fruit enlargement
• Improved fruit shape
• Increased fruit weight
• Seedless fruit production (parthenocarpy)

6. Delaying Senescence

GA₃ delays:

• Leaf yellowing
• Fruit aging
• Chlorophyll degradation

This helps maintain post-harvest quality in some crops.

7. Enzyme Production

GA₃ induces several hydrolytic enzymes:

• α-Amylase
• Protease
• Lipase
• RNase

These enzymes mobilize stored food reserves during seed germination

 

----------- BUY NOW ------------

                               (CLICK ON BUY NOW)

----------BUY NOW------------

AGRICULTURAL BENEFITS 

• Faster plant growth
• Uniform germination
• Better flowering
• Improved fruit setting
• Larger fruits
• Increased yield
• Better crop quality
• Reduced premature fruit drop
• Enhanced market value

Crop	Purpose
Grapes	Berry enlargement
Rice	Seedling vigor
Sugarcane	Increased cane length
Tomato	Fruit set
Citrus	Reduce fruit drop
Apple	Fruit size
Pear	Fruit enlargement
Strawberry	Bigger fruits
Cotton	Seed germination
Tea	Shoot growth
Banana	Bunch development
Ornamental flowers	Longer stems and improved flowering

 

RECOMMENDED DOSAGE (GENERAL GUIDELINE)

Crop Stage	GA₃ Concentration
Seed treatment	50–200 ppm
Vegetative stage	20–50 ppm
Flowering	20–40 ppm
Fruit enlargement	20–80 ppm

 

Note: The exact dose depends on the crop, variety, growth stage, and manufacturer recommendations.

CONCLUSION