Seed Adaptations - Topic 1 (Plant Science II), Element 5 Flashcards
What is seed dormancy?
A condition where a viable seed does not germinate despite having the right environmental factors present
Dormancy can be innate or induced.
What are the two categories of seed dormancy?
Innate dormancy and induced dormancy
Innate dormancy develops before the seed is shed; induced dormancy develops later in response to environmental conditions.
What is breaking dormancy?
The process of removing dormancy stimuli to allow seed germination
This can involve various techniques.
What ecological purpose does dormancy serve for plants?
Ensures seeds germinate in Spring and spreads germination over time
This increases survival chances for seedlings.
What is the stale seedbed technique?
Cultivating an area for sowing before it is needed to allow weed seeds to germinate and be removed
This helps manage soil seed banks.
What is the impact of climatic conditions on dormancy?
Dormancy type influences germination timing based on the species’ native climate
For example, cooler climates delay germination until warmer weather.
What are hard seed coats?
Thick or waxy seed coats that prevent water absorption and gas exchange
These seeds require damage to the coat for germination.
What are chemical inhibitors in seeds?
Chemicals that prevent germination until they are removed or altered
This can occur through various environmental stimuli.
What is after-ripening?
A period required for some seeds to develop before they can germinate
This often occurs under warm, dry conditions.
What is scarification?
A method of damaging the seed coat to promote germination
Techniques include rubbing with sand or nicking with a knife.
What is soaking in the context of seed dormancy?
Drenching seeds to leach out inhibitors and soften seed coats
Soaking in hot water can be particularly effective.
What is stratification?
Subjecting seeds to a period of warm or cold, moist conditions to break dormancy
Mimics natural seasonal cycles.
What is warm, moist stratification?
Soaking seeds and placing them in moist conditions at 15-24°C for 4 weeks to 3 months
This helps start the germination process.
What is cold, moist stratification?
Placing seeds in moist conditions at 1-7°C for 4 weeks to 5 months
Required for many temperate and alpine species.
What is smoke treatment for seeds?
A method that uses chemicals from vegetation smoke to promote germination
Particularly effective for some Australian and southern African species.
True or False: Dormancy ensures seeds germinate at unsuitable times.
False
Dormancy prevents germination during unfavorable conditions.
What are plant growth regulators (PGRs)?
Hormones that help in the development and breaking of dormancy in seeds
They can be applied to overcome dormancy in some species.
Na
What is one advantage of seeds germinating only in light?
Prevents germination under the shade of other plants
This ensures better survival rates for seedlings.
What is the germination time for Fraxinus excelsior seeds after dispersal?
Approximately 18 months
They require warm and then cold stratification.
What are the key adaptations of seeds?
Adaptations include:
* Quantity of seed produced
* Dispersal mechanism
* Dormancy mechanisms
* Seed coats
* Storage of fats and oils
* Orthodox
* Recalcitrant
Orthodox seeds can tolerate desiccation, while recalcitrant seeds cannot.
What environmental conditions are necessary for seed germination?
Conditions include:
* Available water
* Oxygen
* Correct temperature
Some species have specific needs for moisture, oxygen, and temperature.
What is the function of the seed coat (testa)?
The seed coat protects the seed from invertebrates, bacteria, fungi, and prevents drying out.
What is the hilum in a seed?
The hilum is the scar where the seed was attached to the ovary.
What is the micropyle’s role in seed anatomy?
The micropyle is a tiny pore that allows the seed to take in water.
What are cotyledons?
Cotyledons are seed leaves; in eudicots and Basal Angiosperms, there are two cotyledons.
What is the endosperm’s role in a seed?
The endosperm is a starchy tissue that contains nutrients for the embryo during germination.
What does the embryo of a seed consist of?
The embryo consists of:
* Plumule (embryonic shoot)
* Radicle (embryonic root)
* Epicotyl (above cotyledons)
* Hypocotyl (below cotyledons)
The embryo has all basic parts of a plant in miniature.
How do monocot seeds differ from dicot seeds?
Monocots have one cotyledon, while dicots have two cotyledons, and the endosperm remains separate from the cotyledon in monocots.
What are endospermous plants?
Endospermous plants store food in endospermic tissue; examples include cereals like wheat and maize.
What are non-endospermous plants?
Non-endospermous plants store food in their cotyledons; examples include legumes like peas and beans.
What is the significance of seed viability?
Seed viability determines how long a seed can remain capable of germinating.
Define epigeal germination.
Epigeal germination is when the cotyledons are pushed above the ground.
Define hypogeal germination.
Hypogeal germination is when the cotyledons remain below ground.
In epigeal germination, which part of the seed elongates?
The hypocotyl elongates.
In hypogeal germination, which part of the seed elongates?
The epicotyl elongates.
What is the role of the coleoptile in monocot seeds?
The coleoptile is a sheath that protects the plumule.
What is the role of the coleorhiza in monocot seeds?
The coleorhiza is a sheath that protects the radicle.
What adaptations help seeds survive in their environment?
Adaptations include:
* Hard seed coats
* Waterproofing
* Heat resistance
* Stomach acid resistance
What are some horticultural methods to enhance germination?
Methods include:
* Providing optimum temperature
* Ensuring moisture
* Ensuring oxygen availability
* Manipulating plant growth regulators
* Removing dormancy mechanisms
Fill in the blank: Seeds of some plants, like orchids, do not contain _______.
[endosperm]
True or False: All seeds require light to germinate.
False
What is seed dormancy?
A condition where a viable seed does not germinate despite having the right environmental factors present
Dormancy can be innate or induced.
What are the two categories of seed dormancy?
Innate dormancy and induced dormancy
Innate dormancy develops before the seed is shed; induced dormancy develops later in response to environmental conditions.
What is breaking dormancy?
The process of removing dormancy stimuli to allow seed germination
This can involve various techniques.
What ecological purpose does dormancy serve for plants?
Ensures seeds germinate in Spring and spreads germination over time
This increases survival chances for seedlings.
What is the stale seedbed technique?
Cultivating an area for sowing before it is needed to allow weed seeds to germinate and be removed
This helps manage soil seed banks.
What is the impact of climatic conditions on dormancy?
Dormancy type influences germination timing based on the species’ native climate
For example, cooler climates delay germination until warmer weather.
What are hard seed coats?
Thick or waxy seed coats that prevent water absorption and gas exchange
These seeds require damage to the coat for germination.
What are chemical inhibitors in seeds?
Chemicals that prevent germination until they are removed or altered
This can occur through various environmental stimuli.
What is after-ripening?
A period required for some seeds to develop before they can germinate
This often occurs under warm, dry conditions.
What is scarification?
A method of damaging the seed coat to promote germination
Techniques include rubbing with sand or nicking with a knife.
What is soaking in the context of seed dormancy?
Drenching seeds to leach out inhibitors and soften seed coats
Soaking in hot water can be particularly effective.
What is stratification?
Subjecting seeds to a period of warm or cold, moist conditions to break dormancy
Mimics natural seasonal cycles.
What is warm, moist stratification?
Soaking seeds and placing them in moist conditions at 15-24°C for 4 weeks to 3 months
This helps start the germination process.
What is cold, moist stratification?
Placing seeds in moist conditions at 1-7°C for 4 weeks to 5 months
Required for many temperate and alpine species.
What is smoke treatment for seeds?
A method that uses chemicals from vegetation smoke to promote germination
Particularly effective for some Australian and southern African species.
True or False: Dormancy ensures seeds germinate at unsuitable times.
False
Dormancy prevents germination during unfavorable conditions.
What are plant growth regulators (PGRs)?
Hormones that help in the development and breaking of dormancy in seeds
They can be applied to overcome dormancy in some species.
Fill in the blank: _______ involves soaking seeds in sulphuric acid to mimic digestion.
Chemical inhibitors
This method is used commercially for specific species.
What is one advantage of seeds germinating only in light?
Prevents germination under the shade of other plants
This ensures better survival rates for seedlings.
What is the germination time for Fraxinus excelsior seeds after dispersal?
Approximately 18 months
They require warm and then cold stratification.
