Breaking dormancy

Analysis: 5% GA3 (Gibberellic Acid)

What Is It?

  • CFIA-registered supplement: Reg. # 2018xxxA, Fertilizers Act
  • The product contains gibberellic acid (GA3), a very potent plant growth regulator that control several processes of crops growth and development.
  • GA3 is the hormone that triggers rice to grow out of the water in the paddies.
  • GA3 promotes plant and flower growth and increased fruit set.
  • It aids in frost protection, overcoming dormancy, and inhibits root formation in cuttings.
  • Applications of very low concentrations can have a profound effect.
  • However, excessive application or higher rates may result in undesirable stem elongation.
  • Timing of application is also crucial for insuring a beneficial effect.
Figure 1. Diagram highlighting the importance of GA3 signaling in breaking dormancy and initiation of germination. Abscisic acid (ABA) controls the opposite effect of GA3.
UTC vs. Treated
Figure 2. Breaking dormancy in potato seed/tuber pieces using GA3.

When & Why Use It?

  • The product is recommended on all crops including field, horticultural and vegetable crops as well as fruit trees, turf and ornamentals.
  • It can be used to break dormancy and enhance emergence in tuber and root crops.
  • GA3 is produced first in the seed to trigger production of the a-amylase that stimulates seed germination.
  • It helps with tolerance to cold and frost conditions early in the season.
  • GA3 is known to increase fruit and seed size.
  • Gibberellins stimulate cell elongation and cause the plants to grow taller after dilution to minimize settlement.
Figure 3. Barley seed germination showing the early involvement of GA3 in the process.
Figure 4. Effect of gibberellins (GA3) on cabbage stem elongation (right) versus untreated check (left).

What To Expect?

  • Better germination and early season establishment.
  • An improved growth and development especially under cool and cold stress conditions.
  • Better seed and fruit sizes.
  • Enhanced yield and quality.
Figure 5. Effect of the treatment of cucumber seedlings with GA3 under cold stress (source: Bai et al., 2016). DM: dry matter.

Application Guidelines

  • Follow the recommended rates and timing listed on the label for each crop and do not exceed the recommendation.
  • Fill spray tank with half of the full volume of water and then add required amount of StimPro-GA3 5%, followed by the remaining water. Add desired amount of surfactant after adding all required water.
  • Agitate vigorously for a minimum of 10 minutes before beginning application.
  • Use appropriate water volume to guarantee good coverage.
  • For full product activity, application should be made under cool, slow-drying weather conditions, preferably early in the morning or late in the day. Avoid hot, windy periods. StimPro-GA3 5% has low solubility in water and cannot be used in high concentrations. In solution, it has limited stability and should be applied as soon as possible.
  • Several factors may affect StimPro-GA3 5% efficacy including:
    • Rainfall within 4–6 hours of application will reduce activity significantly.
    • Very early maturing varieties may not respond to StimPro-GA3 5%.
    • Trees under stress because of low soil moisture, nutrient deficiency, severe weed competition, insect, disease or rodent damage may not respond to StimPro-GA3 5%.
    • Inadequate spray coverage.
    • A heavy crop load (high fruit/leaf ratio) may reduce effectiveness.
  • All necessary precautions should be taken to avoid spray drift into adjoining residential properties, orchards, aquatic habitats and roadways.

*StimPro-GA3 is a trademark of EZ-Gro Inc.