Photosynthesis

• Green plants are known as the food factories of the world because almost all the food on Earth comes directly or indirectly from green plants
• Green plants use water and carbon dioxide to make food using light energy from the sun, a process known as photosynthesis
• Photosynthesis is considered the primary process by which green plants produce their food
• Plants are autotrophs since they can make their own food
• Sunlight is trapped by pigments, such as chlorophyll, found in chloroplasts
• Chloroplasts convert light energy, carbon dioxide, and water into glucose and oxygen
• Glucose is a simple sugar that is used as an energy source for the plant and to make other substances such as starch
• During photosynthesis, oxygen is released into the air through small pores called stomata in the leaves
• The equation for photosynthesis is:

  Carbon Dioxide + Water + Light energy (trapped by chlorophyll) → Glucose + Oxygen
• Green plants are known as the food factories of the world because almost all the food on Earth comes directly or indirectly from green plants
• Green plants perform photosynthesis using carbon dioxide, water, and light energy from the Sun
• Photosynthesis is the process by which green plants make their food
• Plants are considered autotrophs because they can produce their own food
• The energy from sunlight is captured by green pigments called chlorophyll, located in chloroplasts within the cells of green leaves
• During photosynthesis, light energy is used to convert carbon dioxide and water into glucose and oxygen
• Glucose, a simple sugar produced during photosynthesis, is used to provide energy for the plant and to create other substances like starch and sucrose
• Plants store substances like starch for later use
• Oxygen produced during photosynthesis is released into the air through tiny pores called stomata
• The process to determine if leaves have carried out photosynthesis involves:

  1. Placing 2-3 leaves in a beaker of hot distilled water for about 10 minutes to soften them

  2. Removing the leaves from the hot water and placing them in another beaker containing ethanol

  3. Carefully heating the leaves in the ethanol for 5-10 minutes to extract chlorophyll pigments

  4. Removing the leaves from the ethanol when they are no longer green and washing them with cold water

  5. Placing the leaves on a Petri dish and adding iodine solution; starch in the leaves turns blue-black when iodine solution is added
• Structure of a leaf:

  • Upper epidermis
  • Mesophyll
  • Lower epidermis
  • Cuticle
  • Cytoplasm
  • Vacuole
  • Chloroplast
  • Nucleus
  • Cell wall
  • Air space
  • Guard cell
  • Stoma
• Cell structure of a leaf includes:

  • Palisade mesophyll
  • Spongy mesophyll
  • Wax cuticle
  • Palisade layer
  • Upper epidermis
  • Spongy layer
  • Lower epidermis
  • Wax cuticle
  • Mesophyll (photosynthetic tissue)