Remedial measures/methods to break dormancy

1. Seed coat treatments

• These treatments are either physical or chemical in nature, and aim at making hard seed coats permeable to water and/ or gases by either cracking or softening the: the process is usually called as scarification

a. Mechanical scarification

• Rotating the seeds in machines having drums with abrasive surfaces
• Rubbing the seed against abrasive surfaces manually. Eg. corainder

b. Chemical scarification

• This is achieved by the use of sulphuric acid, Hcl, NaOH, alcohol, acetone, oxidizing agents etc
• Treating in 3% nitric acid solution for 6-8 hrs can relieve the seed dormancy in Rice
• Among the several methods available the most suitable method to break seed dormancy at farmers level is nitric acid treatment
• Soaking the seed in 0.1 N nitric acid i.e. 6.3 ml per lit. of water for 12 to 24 hours effectively breaks the seed dormancy in less or moderately dormant varieties
• Scarifications must be done with caution and care; otherwise it may damage the seeds
• Scarification may be achieved by rubbing the seeds on a sand paper manually or by using a mechanical scarifier
• The seed coat may be pierced by a needle or a small incision may be made in it at the abaxial end of the seed

2. Embryo treatments

• When dormancy is due to factors located within the embryo such treatments have to be applied that capable of inducing the embryo to resume growth
• Some of the common treatments are briefly described below

a. Stratification

• Stratification is the incubation of seeds at a suitable low temperature (usually, 0-5 °C) over a moist substratum before transferring them to a temperature optimum for germination; it is a common embryo treatment designed to overcome dormancy

b. High temperature treatment

• In some plants incubation at 40-50 °C for few hours to 1-5 days may be effective in overcoming dormancy
• Care should be taken that the moisture content of seeds should be less than 15%
• For example, rice seeds having less than 15% moisture are incubated at 40-50 °C for 4-5 days for overcoming dormancy

3. Chemical / Hormonal treatments

• The growth regulators most commonly used for this purpose are GA (100 ppm is the most commonly used concentration ) and kinetin (concentration range , usually 10-15 ppm)
• Benzyl adenine at 2 ppm and ethrel at 250 ppm are effective in breaking seed dormancy of sunflower
• Ethrel 75 ppm and GA at 60-75 ppm are effective in controlling seed dormancy in groundnut
• Potassium nitrate (0.2%) and thiourea (0.5 to 3%)
• Thiourea breaks the dormancy of seeds requiring light and or chilling e.g. lettuce, gladiolus etc.

4. Miscellaneous Treatments

• Exposing the seeds of many species to red or white light leads to a termination of dormancy
• For example, lettuce seeds exposed to red light at 660 nm or to white light are induced to germinate
• Generally, seeds are placed initially in red light, and they subsequently transferred to dark or white light for germination