Photosynthesis

• Photosynthesis


  1. Takes place in the leaves

  2. Takes place in chloroplasts

  3. Chlorophyll absorbs light energy

  4. Converts carbon dioxide and water into glucose and oxygen
• Photosynthesis is an endothermic reaction, where energy is transferred from the environment to chloroplasts by light
• Carbon dioxide and water supply for photosynthesis

  1. Carbon dioxide diffuses into leaves through stomata

  2. Water is taken up from soil by roots and transported to leaves via xylem
• Products of photosynthesis


  • Glucose is the main product
  • Oxygen is also produced but not as important
• Uses of glucose produced by photosynthesis

  • Cellular respiration
  • Making cellulose
  • Making starch
  • Making amino acids
  • Making oils and fats
• Plant growth rate is often dependent on the rate of photosynthesis
• Factors affecting the rate of photosynthesis are light intensity, temperature, carbon dioxide concentration, and the amount of chlorophyll
• Levels of organization in plants

  • Cells
  • Tissues
  • Organs
  • Organ systems
• Leaf

  An organ that, along with a stem and roots, forms an organ system for transport of substances around the plant
• Photosynthesis


  1. Requires carbon dioxide and water

  2. Water transported from soil by roots and xylem

  3. Carbon dioxide diffuses into leaf through stomata

  4. Carbon dioxide enters spongy mesophyll tissue

  5. Carbon dioxide diffuses to palisade mesophyll layer where photosynthesis occurs

  6. Sugars produced are transported to rest of plant by phloem
• Stomata

  Tiny holes in lower epidermis that allow carbon dioxide to enter and water vapor to exit
• Plant is short of water

  Guard cells are flaccid, stomata close
• Meristem tissue


  Plant form of stem cells, found at growing tips of roots and shoots, can differentiate into many cell types
• Most stomata are on underside of leaves to reduce water evaporation