seeds Flashcards
What is a seed?
A seed is a tiny embryonic plant encased in a seed coat, containing nutrition for its development.
What are the functions of a seed?
- Reproduction: Most flowering plants reproduce through seeds.
- Container of the Embryo: Protects and nurtures the developing embryo until maturity.
- Storage of Food: Stores nutrients in the cotyledon or endosperm, especially in monocots.
What are the advantages of seeds for plants?
- Dormancy Maintenance: Seeds remain inactive until favorable environmental conditions arise.
- Protection: Shields young plants at vulnerable developmental stages.
- Nutritional Support: Contains food reserves for the embryo until photosynthesis begins.
- Dispersal: Facilitates the spread of plants to new areas.
What are the external parts of a seed?
- Seed coat (Testa): Protective outer layer.
- Hilum: A scar marking where the seed was attached to the parent plant.
- Micropyle: An opening for water absorption during germination.
What are the internal parts of a seed?
- Cotyledon: First leaves of the seed; stores nutrients for the embryo.
- Epicotyl (Plumule): Develops into the shoot, leaves, and upper stem.
- Hypocotyl: Develops into the lower stem.
- Radicle: The embryonic root; grows into the plant’s root system.
What are the features of monocot seeds?
- Cotyledon (1): Stores energy as oils and proteins.
- Endosperm: Surrounds and stores food for the embryo.
- Coleoptile: Protective sheath for the shoot.
- Coleorhiza: Protective sheath for the root.
What are the features of dicot seeds?
- Cotyledons (2): Nutritional reserve for the embryo.
- Plumule: Develops into the shoot system.
- Radicle: Forms the primary root.
What are the steps of seed germination?
- Imbibition: Absorption of water by the seed.
- Activation of Enzymes: Converts stored starches into sugars for the embryo.
- Radicle Emergence: The first visible sign of germination.
- Growth of Shoot and Root: Development continues with elongation.
What is seed dormancy?
A state of low metabolic activity to survive unfavorable conditions.
What factors can break seed dormancy?
- Vernalization: Cold treatment.
- Scarification: Mechanical or chemical processes to soften the seed coat.
- Water Leaching: Washes away inhibitors in the seed coat.
- Fire or Heat Treatment: Common in some species.
What are the types of germination?
- Hypogeous Germination: Epicotyl elongates; cotyledons stay underground.
- Epigeous Germination: Hypocotyl elongates; cotyledons are pushed above ground.
- Vivipary: Seeds germinate while still attached to the parent plant.
What is seed dispersal?
Seed dispersal is the process of scattering or transporting seeds from the parent plant to different locations.
What is the importance of seed dispersal?
- Increases the chances of seeds landing in suitable environments for germination.
- Reduces competition for resources among seedlings and parent plants.
- Helps plants colonize new areas, enhancing biodiversity.
What are the modes of seed dispersal?
- Wind Dispersal (Anemochory): Lightweight and aerodynamic seeds.
- Animal Dispersal (Zoochory): Seeds transported by animals.
- Water Dispersal (Hydrochory): Buoyant seeds for travel across water.
- Explosion/Expulsion Dispersal (Autochory): Seeds ejected from pods.
What is ant-mediated seed dispersal?
A mutualistic relationship where ants collect seeds with elaiosomes, consuming them and discarding seeds in nutrient-rich piles.
