Final Final Final Revision Flashcards
What is Double Fertilization?
A unique process in angiosperms where two sperm cells fertilize cells within the ovule: one fuses with the egg cell forming a zygote, and the other combines with two polar nuclei to form the triploid endosperm.
What are the steps leading to Double Fertilization?
- Pollen lands on the stigma and germinates.
- A pollen tube grows down the style toward the ovary.
- The tube penetrates the ovule through the micropyle.
- Two sperm cells travel through the pollen tube into the ovule.
What is formed when one sperm cell fertilizes the egg cell?
A diploid (2n) zygote, which will develop into the embryo.
What is the role of the second sperm cell in Double Fertilization?
It fuses with the two polar nuclei in the central cell, forming a triploid (3n) endosperm.
What is the significance of Double Fertilization?
- Ensures synchronized development of the embryo and its food supply.
- Contributes to efficient resource allocation in seed development.
What is Germination?
The process by which a seed emerges from dormancy and begins to sprout, developing into a new plant under favorable conditions.
What are the stages of Germination?
- Imbibition
- Enzyme Activation
- Respiration Increase
- Radicle Emergence
- Shoot Emergence
What is Imbibition in the context of germination?
The seed absorbs water, swelling and softening the seed coat.
What role does oxygen play in germination?
Required for aerobic respiration.
Define Physical Dormancy.
Hard seed coat prevents water uptake.
What is Scarification?
Physically breaking or softening the seed coat to break dormancy.
What are the components of a flower?
- Calyx
- Corolla
- Androecium
- Gynoecium
What is the function of sepals?
Protect developing buds.
What does the Androecium consist of?
The male reproductive part made up of stamens.
What is Actinomorphic symmetry?
Radial Symmetry; multiple planes divide the flower into mirror-image halves.
What is Secondary Thickening?
The increase in the girth (diameter) of stems and roots in woody plants, resulting from the activity of lateral meristems.
What are the lateral meristems involved in secondary thickening?
- Vascular Cambium
- Cork Cambium (Phellogen)
What does the vascular cambium produce?
Secondary xylem (wood) inward and secondary phloem outward.
What is the significance of secondary thickening?
- Provides structural support.
- Facilitates increased transport capacity.
What do annual growth rings represent?
Visible rings in the cross-section of woody stems, each typically representing one year of growth.
What are Auxins?
Hormones that promote cell elongation by increasing the plasticity of the cell wall.
What do Gibberellins stimulate?
- Stem elongation
- Seed germination
- Flowering
What is the role of Cytokinins?
Promote cell division and differentiation, delay leaf senescence.
What does Ethylene regulate?
- Fruit ripening
- Leaf abscission
- Response to mechanical stress
What is the function of Abscisic Acid (ABA)?
Induces seed dormancy and helps plants respond to environmental stresses like drought.
What is the location and function of Shoot Apical Meristems (SAM)?
Located at the tips of shoots; responsible for the primary growth and elongation of the plant.
What are the zones of the SAM?
- Central Zone (CZ)
- Peripheral Zone (PZ)
- Rib Zone (RZ)
How is the SAM maintained?
A balance between cell division and differentiation, regulated by genetic factors and hormonal signals.
What role does the SAM play in organogenesis?
Initiates the formation of lateral organs such as leaves, flowers, and branches.
What is the structure of the Cell Wall?
A rigid layer composed mainly of cellulose, providing structural support and protection.
What are Plasmodesmata?
Channels between adjacent plant cells that allow for the transport of substances and communication.
What is the function of the Vacuole?
Stores nutrients, waste products, and helps maintain turgor pressure.
What do Chloroplasts contain?
Chlorophyll, the site of photosynthesis.
What is the primary function of Mitochondria?
Generate ATP through cellular respiration.
What is the Seed Coat (Testa)?
The protective outer covering of the seed that prevents desiccation and regulates water uptake.
What does the Embryo consist of?
- Radicle (future root)
- Plumule (future shoot)
- Cotyledons
What are Cotyledons?
Seed leaves that store/transmit nutrients.
What is the function of Endosperm?
A nutrient-rich tissue that provides energy.
What is the Hypocotyl?
The embryonic stem located below the cotyledons.
What does the Epicotyl develop into?
The shoot system.
What is the Plumule?
The shoot tip of the embryo that contains leaf primordia.
