Seed dormancy and methods to break dormancy

1. Introduction

1. Seed dormancy is a state in which seeds do not germinate even under favorable conditions.
2. It ensures the survival of seeds by preventing premature germination.
3. Dormancy helps seeds to remain viable during unfavorable environmental conditions.

2. Types of Seed Dormancy

1. Exogenous Dormancy

1. Caused by external factors like a hard seed coat or chemical inhibitors.
2. Includes Physical, Mechanical, and Chemical Dormancy.

2. Endogenous Dormancy

1. Due to internal factors like immature embryos or metabolic inhibitors.
2. Includes Embryo Dormancy and Physiological Dormancy.

3. Combined Dormancy

1. Involves both exogenous and endogenous factors.
2. Example: Apple, Oak seeds.

3. Causes of Seed Dormancy

1. Physical Barriers

1. Hard seed coat prevents water and oxygen entry (e.g., Pea, Lotus).
2. Seeds require mechanical or chemical breakdown to germinate.

2. Chemical Inhibitors

1. Seeds contain growth inhibitors like abscisic acid (ABA).
2. Leaching out these inhibitors is necessary for germination.

3. Immature Embryo

1. Some seeds require further development before germination.
2. Example: Ginkgo, Orchid seeds.

4. Light and Temperature

1. Some seeds need specific light conditions (e.g., Lettuce).
2. Temperature extremes can also delay germination.

4. Methods to Break Seed Dormancy

1. Scarification

1. Breaking the seed coat to allow water and oxygen entry.
2. Methods:
   • Mechanical Scarification: Rubbing seeds with sandpaper.
   • Chemical Scarification: Treating with acids like H2SO4.
   • Thermal Scarification: Exposing seeds to hot water.
3. Example: Lotus, Acacia seeds.

2. Stratification

1. Exposing seeds to low or high temperatures to stimulate germination.
2. Cold stratification (chilling) is used for Apple, Walnut seeds.
3. Warm stratification is used for Palm seeds.

3. Leaching

1. Washing out chemical inhibitors from seeds using water.
2. Common in seeds of Tomato, Citrus.

4. Hormonal Treatment

1. Using growth hormones to stimulate germination.
2. Gibberellins (GA) help break dormancy in barley seeds.

5. Light and Oxygen Treatment

1. Seeds of Lettuce need light for germination.
2. Providing oxygen enhances germination in waterlogged seeds.

5. Importance of Breaking Dormancy

1. Ensures timely germination for crop production.
2. Essential for agriculture, forestry, and conservation.
3. Helps in seed banking and plant breeding.

6. Conclusion

1. Seed dormancy helps seeds survive harsh conditions.
2. Methods like scarification, stratification, and hormonal treatment help break dormancy.
3. Understanding dormancy is important for crop production and biodiversity conservation.