Germination Flashcards
What are endospermic seeds?
Seeds that contain endosperm tissue for energy storage
Gibberellic acid produced by the embryo triggers enzyme production, which converts starch to sugar in the aleurone layer.
What role does gibberellic acid play in endospermic seeds?
Triggers enzyme production
These enzymes convert starch to sugar, which is then used for embryo growth.
In non-endospermic seeds, where is energy stored?
In cotyledons
Storage conversion happens during seed development.
What initiates germination in non-endospermic seeds?
Water acts as a catalyst
Various enzymes like amylase, lipase, and protease break down stored nutrients.
What distinguishes monocots from dicots?
Monocots have one seed leaf; dicots have two seed leaves
Both have a root cap to protect the radical during emergence.
What is epigeal germination?
Cotyledons emerge above the soil
Examples include sunflower and onion.
What is hypogeal germination?
Cotyledons remain below the soil
An example is peas.
What is innate dormancy?
Begins on the mother plant and involves hormones like abscisic acid
Requires an after-ripening period.
What is induced dormancy?
Occurs when germination starts but is prevented
It is hard to break once established.
What causes enforced dormancy?
Unfavorable environmental conditions
Such as lack of water, oxygen, light, or suitable temperature.
List natural methods to break dormancy.
- Soil abrasion
- Fire exposure
- Freeze/thaw cycles
- Leaching of inhibitors
- Digestive acids
- Bacterial/fungal action
These methods help in overcoming dormancy naturally.
List artificial methods to break dormancy.
- Scarification (sandpaper treatment)
- Heat treatment
- Stratification (0-5 degrees followed by warmth)
- Chemical treatment (acid solutions)
- Water soaking
These methods are applied to facilitate germination.
What are the growth phases of seedlings?
- Initially heterotrophic
- Becomes autotrophic
- Growth rate increases after becoming autotrophic
The transition to autotrophic growth is crucial for survival.
What is the critical period in seedling development?
Unfavorable conditions during transition can be fatal
It is essential to establish autotrophic growth before seed reserves exhaust.
What are the practical applications of seeding timing?
- Autumn grass seeding preferred over spring
- Better soil temperature conditions
- Reduced risk of drought
- More consistent moisture availability
- Better establishment rates
These factors contribute to successful seedling development.
