Angiosperm Reproduction and Development Study Guide

Angiosperms: Defined as flowering plants (Vrugbeginsel). * Characterization: Angiosperms are characterized by having ovules that are enclosed within an ovary.
Flower Function: The flower serves as the specific organ of sexual reproduction. * Pollinator Attraction: One primary function of the flower is to attract pollinators to facilitate reproduction. * Hermaphrodites: Some flowering plants are hermaphroditic, meaning they produce both male and female gametes within the same structure.
Gamete Locations: * Male Gametes: Contained inside pollen grains, which are produced by the anthers. * Female Gametes: Contained inside ovules, which are enclosed and protected by the ovary.

Stamen (Male Part): Consists of the following components: * Anther: The site of pollen production. * Filament: The stalk that supports the anther.
Carpel / Pistil (Female Part): Consists of the following components: * Stigma: The uppermost part that receives pollen. * Style: The tube connecting the stigma to the ovary. * Ovary: The enlarged basal portion containing the ovules.
Supporting and Accessory Structures: * Petal: Often brightly colored to attract pollinators. * Sepal: Leaf-like structures that protect the flower bud. * Ovule: Found inside the ovary; contains the female gamete. * Receptacle: The thickened part of a stem from which the flower organs grow. * Pedicel: The stalk of an individual flower.

Composition: The stamen is composed of the anther and the filament.
Anther Function: Anthers are responsible for producing pollen grains, which house the male gametes.
Filament Function: The filament holds the anther in a favorable position to ensure pollen is effectively released.

Stigma: Described as the "sticky" part of the carpel. Its primary role is to receive pollen grains.
Style: Acts as a connector between the stigma and the ovary. It serves to hold the stigma in a favorable position to receive pollen from pollinators or the environment.
Ovary: This structure contains the ovules (female gametes). * Post-Fertilization Transformation: Once a gamete is fertilized, the ovule develops into a seed, and the surrounding ovary develops into a fruit.

Definition of Pollination: Pollination is the transfer of pollen from the anther to a stigma.
Mechanism: When an anther is mature, it splits open to discharge the pollen.
Types of Pollination: * Self-Pollination: Pollen is transferred from the anther to the stigma on the same flower or other flowers on the same plant. * Genetic Outcome: Results in no genetic variation. * Cross-Pollination: Pollen is transferred from the anther of a flower on one plant to the stigma of a flower on a different plant of the same species. * Genetic Outcome: Results in genetic variation.

Temporal Separation: In bisexual flowers, the anther and the stigma may ripen at different times to prevent self-fertilization.
Unisexual Flowers: Some flowers are naturally unisexual, ensuring they cannot pollinate themselves.
Structural Barriers: The stigma may be positioned physically above the anthers, making it difficult for pollen from the same flower to reach it.
Human Intervention: Plant breeders may manually remove anthers to prevent self-pollination, though this is not a natural process.

Visual and Olfactory Traits: These flowers typically have no scent, no nectar, and no bright petals, as they do not need to attract animal pollinators.
Physical Positioning: Flowers are often worn high on the plant to ensure maximum exposure to the wind.
Flower Structure: Flowers are small and reduced, lacking a cup or crown structure.
Anther and Filament Adaptation: Anthers are large and well-exposed. Filaments are long and flexible to catch the breeze.
Pollen Characteristics: The plant produces large quantities of very small, light, and non-sticky pollen.
Stigma Adaptation: The stigma is long and feathery with a large surface area specifically designed to capture wind-borne pollen.

Visual Cues: Flowers feature bright colors to attract insects. * Bee Vision: Note that bees cannot see the color red. * Evening Pollinators: White flowers are common for evening pollinators like moths.
Olfactory Cues: Flowers produce a sweet scent to attract butterflies and bees.
Food Rewards: The flower produces nectar as a food source for insects.
Pollen Characteristics: Pollen is sticky, allowing it to easily adhere to the insect's body.
Structural Mechanics: Stamens and stigmas are positioned inside the flower. This ensures that pollen on the insect's body can rub off onto the sticky stigma as the insect enters the flower.

Visual Cues: Flowers are brightly colored, frequently appearing in shades of red or orange to attract birds.
Food Rewards: Large quantities of nectar are produced to provide sufficient food for birds.
Sense of Smell: These flowers have little or no smell because birds generally have a weak sense of smell.
Flower Shape: Flowers are often shaped like a trumpet.
Structural Positioning: Stamens and the stigma protrude from the flower (exerted).
Stem Structure: Flowers are often carried in clusters on the tips of long, solid, leafless stems (Silva krie), making them more accessible for hovering birds.

Definition: Fertilization is the joining of $2$ haploid cells (gametes) to form a single diploid zygote.
Timing: Fertilization always takes place after pollination has occurred.
Sequence of Events: 1. Pollen lands on the stigma. 2. A pollen tube develops and grows downward along the style and into the ovule. 3. The pollen tube carries the male gamete. 4. The male gamete enters the ovule, and fertilization occurs. 5. Following fertilization, the development of the embryo begins.

Zygote Development: After fertilization, the zygote undergoes mitosis to develop into an embryo.
Embryo Components: The embryo consists of: * Cotyledons: Also known as seed leaves. * Radicle: Becomes the root of the plant. * Plumule: Becomes the shoot of the plant.
Endosperm: The remaining part of the ovule develops into endosperm tissue, which provides nutrition.
Seed Coat: The outer covering of the ovule forms the seed coat, also known as the testa.

Mechanism: The ovary grows in size while the seed is being formed; this matured ovary becomes the fruit.
Importance of Fruits: * Protection: Fruits protect the developing seeds. * Dispersal: Fruits help in the dispersal of seeds away from the parent plant.