Plant cell Organisation

• 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. Photosynthesis occurs in palisade mesophyll layer
• Leaf structure


  • Upper epidermis
  • Palisade mesophyll
  • Spongy mesophyll
  • Lower epidermis with stomata
• Stomata


  Allow carbon dioxide to enter but cause water loss
• Guard cells


  Control opening and closing of stomata based on water status
• Stomata mostly on underside of leaf to reduce water loss
• Meristem tissue


  Plant form of stem cells, found at growing tips, can differentiate into many cell types
• Epidermal cells


  Very thin cells that form the upper and lower epidermis of a leaf
• Upper epidermis


  • Transparent to allow light to pass through
  • Covered in a waxy cuticle to reduce water evaporation
• Lower epidermis


  • Contains tiny pores called stomata
  • Has guard cells on either side of the stomata
• Palisade mesophyll


  Consists of palisade cells packed full of chloroplasts that contain chlorophyll for photosynthesis
• Spongy mesophyll


  • Full of air spaces to allow carbon dioxide and oxygen diffusion
• Xylem


  Transports water and dissolved mineral ions from roots to stem and leaves
• Phloem


  Transports dissolved sugars produced by photosynthesis from leaves to rest of plant
• Translocation


  Movement of sugars through phloem tissue
• Meristem tissue


  Contains stem cells that can differentiate into different plant tissues
• Meristem tissue is found in growing tips of shoots and roots