Reproduction In Plants

• Sexual reproduction


  Reproduction involving the fusion of male and female gametes
• Female parent


  Produces female gamete (ovum) through meiosis
• Asexual reproduction

  Reproduction from a single parent, without the fusion of gametes
• Reproduction


  The ability of an organism to produce offspring of their own kind to keep their species
• One parent


  Organism that reproduces asexually
• Male parent


  Produces male gamete (sperm) through meiosis
• Gamete


  Haploid cell containing half the number of chromosomes (23)
• Fertilization


  The fusion of male and female gametes to form a zygote
• Zygote


  Diploid cell which contains the full number of chromosomes (46) due to fertilization
• Advantages of asexual reproduction

  • Rapid
  • Simple
  • Big number of offspring
  • Keeps good character
• Disadvantages of asexual reproduction

  • No variation
  • No evolution
• Advantages of sexual reproduction

  • There is variation
  • There is evolution
• Disadvantages of sexual reproduction

  • Slow
  • Complicated
  • Small number of offspring
  • Good characters in parents may not be transferred to the offspring
• Asexual reproduction


  • Binary fission in bacteria
  • Spore formation in bread mould fungus
  • Tuber formation in potato plant
• Tuber formation in potato plant

  1. Stem of potato plant produces branches that grow downwards (underground stems)

  2. Leaves make photosynthesis and transport food as starch to underground stems

  3. Parent plant dies, leaving tubers in soil

  4. Each tuber has eyes and buds that grow into new root and shoot, forming new plants
• Flower


  • Sepals (small green leaves for protection)
  • Petals (large colored leaves to attract insects)
  • Male organs (anther produces pollen grains)
  • Female organs (stigma receives pollen, style carries it to ovary which produces ovules)
• Pollination


  Transfer of pollen grains from anther to stigma
• Types of pollination


  • Self-pollination
  • Cross-pollination
• Self-pollination


  Occurs in bisexual flowers
• Advantages of self-pollination


  • Do not need wind or insect
  • No waste of pollen grains
• Disadvantages of self-pollination


  • Less variation
  • Less evolution
  • More homozygous genotypes, so bad recessive characters are more likely to be expressed
• Cross-pollination


  Occurs in unisexual or bisexual flowers
• Advantages of cross-pollination


  • More variation
  • More evolution
  • More heterozygous, less homozygous genotypes, so bad recessive characters are less likely to be expressed
• Disadvantages of cross-pollination


  • Need wind or insect
  • Waste of pollen grains
• Insect pollination


  1. Insects attracted by color, scent and nectar

  2. Insects brush against anthers, picking up pollen grains

  3. Pollen grains from insect's body stick to stigma of next flower
• Fertilization


  1. Pollen tube grows down style to ovule

  2. Male and female nuclei fuse to form zygote

  3. Zygote divides to form embryo
• Micropyle


  Pore that allows entry of pollen tube to ovule to deliver male nuclei for fertilization
• Steps after fertilization


  1. Sepals dry and fall off

  2. Style withers

  3. Ovary develops into fruit with seeds
• Structure of seed includes testa, stored food, radicle, plumule