Seed dormancy

Definition

Seed dormancy is a physiological state in which seeds enter a period of suspended growth, preventing germination even under favorable environmental conditions. This mechanism is crucial for plant survival, allowing seeds to remain viable until the timing is right for germination, ensuring that they do not sprout prematurely and are better suited to face the challenges of their environment.

5 Must Know Facts For Your Next Test

1. Seed dormancy can be triggered by environmental factors such as temperature, moisture levels, and light, allowing seeds to time their germination for optimal survival conditions.
2. There are different types of seed dormancy, including physical dormancy (due to hard seed coats), physiological dormancy (involving metabolic changes), and morphological dormancy (where the embryo is not fully developed).
3. Breaking seed dormancy often requires specific environmental cues, which can include seasonal changes like winter cold or fire in certain ecosystems.
4. Seed dormancy is an adaptive trait that enhances the chances of successful establishment for plant species in variable environments.
5. Some plants have evolved strategies like serotiny, where seeds remain dormant in cones or fruits that open only after fire or extreme conditions, ensuring germination at the right moment.

Review Questions

• How does seed dormancy enhance the survival chances of plant species in changing environments?
  • Seed dormancy allows plants to time their germination for optimal conditions, which is vital for survival. By remaining dormant, seeds avoid sprouting during unfavorable conditions, such as droughts or extreme temperatures. This ensures that when they do germinate, they have a better chance of establishing successfully and contributing to the population's resilience in a changing environment.
• Compare and contrast physical and physiological seed dormancy, providing examples of each type.
  • Physical seed dormancy occurs when a seed's hard outer coat prevents water absorption and gas exchange necessary for germination. An example is the seeds of legumes, which often require scarification to break dormancy. In contrast, physiological seed dormancy involves internal factors that inhibit germination despite favorable external conditions; an example is many temperate tree species whose seeds may not germinate until they have undergone cold stratification. Both types serve to ensure that seeds only germinate under suitable conditions.
• Evaluate the role of environmental cues in breaking seed dormancy and how this impacts plant distribution and community dynamics.
  • Environmental cues such as temperature fluctuations, moisture availability, and light exposure play critical roles in breaking seed dormancy. For instance, some seeds require cold stratification to trigger germination, which can limit their distribution to regions with specific climatic conditions. Additionally, these cues can synchronize germination within a population, promoting establishment and competition among seedlings. This dynamic influences community structure by determining which species thrive in a given habitat based on their dormancy-breaking requirements and timing.

Related terms

Germination: The process by which a seed develops into a new plant, involving the sprouting of the embryo and the emergence of the seedling.

Endosperm: A tissue produced within the seeds of most flowering plants that provides nutrition to the developing embryo.

Stratification: A process involving exposing seeds to a period of cold temperatures to break dormancy and promote germination.