Biology: Sexual Reproduction in Flowering Plants

Study Notes

Self-incompatibility: the inability of a flower to fertilize itself with its own pollen
Mechanisms to prevent self-fertilization:
- Genetic incompatibility: genes that control pollen growth and pistil recognition prevent self-pollination
- Physical barriers: structures in the flower that prevent self-pollination (e.g., stamen and pistil arrangement)
- Chemical barriers: chemical signals that prevent self-pollen from germinating or growing on the stigma

Fruit formation:
- Ovary development: after fertilization, the ovary grows and matures into a fruit
- Pericarp differentiation: the ovary wall differentiates into exocarp, mesocarp, and endocarp
Seed formation:
- Embryo development: the zygote develops into an embryo
- Endosperm development: the fertilized central cell develops into the endosperm, providing nutrients to the embryo

Stages of embryo development:
1. Zygote formation: fusion of sperm and egg nuclei
2. Embryo formation: series of cell divisions and differentiation
3. Organogenesis: formation of root, stem, and leaf primordia
Embryo structure:
- Radicle (primary root)
- Hypocotyl (stem)
- Cotyledon (seed leaf)

Types of pollination:
- Self-pollination: pollination within the same flower
- Cross-pollination: pollination between different flowers
Agents of pollination:
- Biotic agents: insects, birds, bats, and other animals
- Abiotic agents: wind, water, and gravity

Process of fertilization:
1. Pollen germination: pollen grain grows a pollen tube
2. Sperm delivery: sperm nuclei are released into the pollen tube
3. Fertilization: sperm nuclei fuse with the egg nucleus and central cell nucleus
Double fertilization:
- Fertilization of the egg nucleus: forms the zygote
- Fertilization of the central cell nucleus: forms the endosperm

Self-incompatibility prevents a flower from fertilizing itself with its own pollen
Genetic incompatibility prevents self-pollination through genes controlling pollen growth and pistil recognition
Physical barriers, such as stamen and pistil arrangement, prevent self-pollination
Chemical barriers, such as chemical signals, prevent self-pollen from germinating or growing on the stigma

Fruit formation occurs after fertilization, where the ovary grows and matures
Ovary wall differentiates into exocarp, mesocarp, and endocarp
Seed formation involves embryo development from the zygote
Endosperm development provides nutrients to the embryo, formed from the fertilized central cell

Embryo development involves three stages: zygote formation, embryo formation, and organogenesis
The radicle develops into the primary root
The hypocotyl develops into the stem
The cotyledon develops into the seed leaf

Fertilization involves pollen germination, sperm delivery, and fertilization of the egg nucleus and central cell nucleus
Double fertilization results in the formation of the zygote and endosperm
The zygote develops into the embryo, while the endosperm provides nutrients to the embryo