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.
