Biology: Plant Reproduction and Pollination

Pollination

• The transfer of pollen from the anther of one flower to the stigma of another
• Can occur through various agents:
  • Biotic: bees, butterflies, hummingbirds, bats
  • Abiotic: wind, water
• Pollination is necessary for fertilization to occur

Gamete Development

• Gametes are reproductive cells: eggs (female) and sperm (male)
• In flowering plants, gametes develop in the following structures:
  • Male gametes (sperm): develop in anthers (microsporogenesis)
  • Female gametes (eggs): develop in ovules (megasporogenesis)

Fertilization

• The fusion of a sperm cell with an egg cell to form a zygote
• In flowering plants, fertilization occurs in the ovary of the flower
• Double fertilization is a unique feature of flowering plants (see below)

Double Fertilization

• A process in which two sperm cells from a pollen grain fuse with two cells in the ovule
  • One sperm fertilizes the egg cell to form a zygote
  • The other sperm fertilizes the central cell to form the endosperm (triploid)
• Double fertilization ensures the formation of both the embryo and the endosperm

Embryogenesis

• The process of embryo development from a zygote
• In flowering plants, embryogenesis occurs in the ovule, leading to the formation of a seed
• The embryo develops into three main parts:
  1. Cotyledons (seed leaves)
  2. Hypocotyl (stem)
  3. Radicle (root)

Post-Fertilization Events

• After fertilization, the ovary develops into a fruit, and the ovules develop into seeds
• The seed coat, endosperm, and embryo make up the mature seed
• The fruit and seed structures vary among flowering plant species

Apomixis

• A type of reproduction in which seeds develop without fertilization
• Apomixis can occur in some flowering plants, bypassing the need for pollination and fertilization
• Apomictic seeds produce offspring genetically identical to the parent plant

Polyembryony

• A phenomenon in which multiple embryos develop from a single fertilized ovule
• Polyembryony can occur in some flowering plants, resulting in multiple seedlings from a single seed

Pollination

• Involves the transfer of pollen from an anther to a stigma, allowing for fertilization to occur
• Can occur through biotic agents like bees, butterflies, hummingbirds, and bats, or abiotic agents like wind and water

Gamete Development

• Gametes are reproductive cells, including eggs (female) and sperm (male)
• Male gametes develop in anthers through microsporogenesis, while female gametes develop in ovules through megasporogenesis

Fertilization

• The fusion of a sperm cell with an egg cell to form a zygote, necessary for seed formation
• In flowering plants, fertilization occurs in the ovary of the flower, and involves double fertilization

Double Fertilization

• A unique process in flowering plants where two sperm cells fuse with two cells in the ovule
• One sperm fertilizes the egg cell to form a zygote, while the other sperm fertilizes the central cell to form the endosperm

Embryogenesis

• The process of embryo development from a zygote, occurring in the ovule
• The embryo develops into three main parts: cotyledons (seed leaves), hypocotyl (stem), and radicle (root)

Post-Fertilization Events

• After fertilization, the ovary develops into a fruit, and the ovules develop into seeds
• The seed coat, endosperm, and embryo make up the mature seed, with varying structures among flowering plant species

Apomixis

• A type of reproduction where seeds develop without fertilization, bypassing pollination and fertilization
• Apomictic seeds produce offspring genetically identical to the parent plant

Polyembryony

• A phenomenon where multiple embryos develop from a single fertilized ovule
• Polyembryony can occur in some flowering plants, resulting in multiple seedlings from a single seed