Flower Reproduction in Plants

Study Notes

Flowers are created by plants to assist with their reproductive process, not for human enjoyment.
Not all plants reproduce using flowers, but many plants, called angiosperms, rely on flowers for reproduction.
Flowers cannot support themselves without the rest of the plant mass, like the stem, leaves, branches, or roots.

Flowers have different parts with distinct names, designated as male, female, or sterile.
Sterile parts include:
- Petal: brightly colored to attract pollinators, helping in flower fidelity.
- Sepal: small leaves that cover and protect the flower, photosynthetic but not directly involved in reproduction.
- Receptacle: the portion of the stem where it attaches to the flower and sepal, providing stability.

Pistil is the collective term for female plant parts, consisting of:
- Style: connects other female parts, forming the "neck" shape.
- Stigma: receives pollen, flat and sticky for successful pollen transfer.
- Ovule: unfertilized, incomplete seeds that will develop into offspring.
- Ovary: holds ovules, which will develop into fruit if the plant is a fruiting angiosperm.
Stamen is the collective term for male parts, consisting of:
- Anthers: produce and hold pollen.
- Filament: holds anthers in place.

Pollen from anthers must reach the stigma, which neither male nor female parts can do alone, similar to humans.
Flowers solve the pollen-to-stigma issue in different ways, including:
- Wind: used by trees, like pine trees, which excrete huge amounts of pollen.
- Pollinators: plants offer nectar and sweet smells to attract pollinators, like bees, which bring pollen to the stigma.
After pollination, the female reproductive organs combine ovule and pollen to create a seed, containing a genetically unique individual plant.
The plant then kills off the flower and focuses on seed dispersal, which can occur through:
- Wind: plants like dandelions forming fluffy, aerodynamic structures called pappus.
- Animals: plants like sweet gum trees growing round, spiky seed pods that latch onto animals.
- Expulsion: rare plants, like the poisonous squirting cucumber, ejecting seeds with force.