Plant Biology Notes

Plant Stems

• Stems:
  • Produce leaves, branches, and flowers.
  • Support plant body.
  • Hold up leaves to increase surface area for photosynthesis.
  • Hold up flowers to help with pollination.
  • Transport materials between roots and shoots.
  • Some stems store materials.
    • Cacti stems store water.
    • Potatoes store starch.
  • Some stems aid in asexual reproduction.
    • Strawberry stolons = runners.
    • Crown.

Plant Leaves

• Leaves:
  • Optimized for absorbing light for photosynthesis.
  • Structures in leaf allow for gas exchange & transpiration.
    • Gas exchange: in plants $CO<em>2$ enters the leaves and $O</em>2$ exits.
    • Transpiration: Loss of water from plant leaves into the atmosphere.

Gas Exchange in Leaves

• $CO_2$ enters through stoma.
• $H<em>2O$ and $O</em>2$ exit through stoma.
• Cuticle.
• Vascular tissue.
• Stoma.
• Guard cells.

Plant Leaves

• Metabolism in plants:
  • Photosynthesis: the process by which plants, algae, and some bacteria use sunlight, carbon dioxide, and water to make food (glucose).
    • $6CO<em>2 + 6H</em>2O \rightarrow C<em>6H</em>{12}O<em>6 + 6O</em>2$
  • Cellular Respiration: the process that releases energy from food in the presence of oxygen.
    • $C<em>6H</em>{12}O<em>6 + 6O</em>2 \rightarrow 6CO<em>2 + 6H</em>2O + ATP$ (energy).

Plant Leaves

• Stomata: (singular, stoma) opening in a leaf or stem that enables gas exchange to occur.
  • Usually on the underside of the leaf.
• Guard cells: Cells on each side of a stoma.
  • Control opening and closing of the stoma.

Plant Leaves

• Leaf Adaptations:
  • Some leaves have functions other than photosynthesis and have become modified:
    • Spines on cactus.
      • Discourage animals from eating plants.
    • Leaves on Venus Fly trap or Sundew.
      • Capture food for additional nutrients.
    • Flower petals.
      • Attract pollinators.

Plant Reproduction

• Plants reproduce both asexually and sexually.
• Asexual reproduction:
  • Also known as vegetative reproduction.
  • Types of vegetative reproduction:
    • Plantlets.
    • Tubers.
    • Cuttings.
    • Runners.