Angiosperm reprod. & Seeding Developmentbio II lab revised 2020

Flower Structure

Stamen: Male reproductive structure, consisting of two main parts.
- Anther: Part of the stamen that produces pollen.
- Filament: The stalk that holds the anther.
Carpel: Female reproductive structure, which includes:
- Stigma: The part of the carpel where pollen lands.
- Style: The stalk linking the stigma and the ovary.
- Ovary: Contains one or more ovules, where fertilization occurs.
- Ovule: Contains the female gametophyte.
Other parts include petals for attraction and sepals for protection.

The carpel has a long style and stigma for pollen landing. The ovary at the base houses ovules. A pistil can be a single carpel or several fused carpels.
The stamen comprises a filament topped by an anther loaded with pollen.

Gametophyte Development: Angiosperm gametophytes are microscopic, developing within the protective tissues of the flower.
Angiosperm Cycle: The cycle begins with the flower’s male and female structures where gametophytes are developed—male in pollen grains from anthers, female in ovules.
Double Fertilization: Involves one sperm fertilizing the egg, forming a diploid zygote, while the other sperm fuses with polar nuclei to form triploid endosperm for nourishment.

After fertilization, each ovule develops into a seed, while the ovary evolves into a protective fruit.
Seed Dormancy: A state allowing seeds to remain viable until favorable conditions for germination. Environmental cues are often necessary to break dormancy.
Germination: Involves imbibition (water uptake), with the radicle emerging first to anchor the plant. In eudicots, a hook forms in the hypocotyl for growth above ground.

Pollen transfer occurs via wind, water, or animals. Wind-pollinated species produce excess pollen to enhance chances of transfer.

Fruits serve to protect seeds and assist in dispersal. They can be classified into:
- Simple Fruits: From one or several fused carpels.
- Aggregate Fruits: From a single flower with multiple carpels.
- Multiple Fruits: Develop from a cluster of flowers (inflorescence).

Mature seeds consist of an embryo, a food supply, and a protective coat. Examples of different seed types include:
- Eudicot Seeds: Have thick cotyledons.
- Monocot Seeds: Have one cotyledon, with specialized structures like scutellum in grasses.

Fruits assist in seed dispersal through various methods: by water, wind, or animals. Techniques include:
- Wind dispersal via lightweight or winged fruits.
- Animal dispersal, including behaviors like seed hoarding or feces dispersion.