Cell diversity in plants

• Palisade Cells

  • long and cylindrical, so that they pack together quite closely but a little space between them air to circulate ; carbon dioxide in these air spaces diffuses into cells
  • they have a large vacuole ao that chloroplasts are positioned nearer to the periphery of the cell, reducing the diffusion distance for carbon dioxide
  • they contain many chloroplasts
  • they contain cytoskeleton threads and motor proteins to move chloroplasts nearer to the upper surface of leaf when sunlight intensity is low, but further down when high
• Guard cells 1

  • found in lower epidermis , contains chloroplasts but doesn't carry out photosynthesis because it doesn't have the enzyme needed for the second stage
  • Light energy is used to provide ATP
  • ATP actively transports potassium ions from surrounding epidermal cells to guard cells , lowering water potential
  • water enters by osmosis from neighbouring epidermal cells
  • Guard cells swell, the tips of the cellulose cell wall is flexible, and rigid where it is thicker;the tips bulge and open the stoma
• Guard cells 2

  • once the stomata is open , air can enter within the spaces beneath palisade cells
  • gaseous exchange can occur, carbon dioxide can diffuse into palisade cells ; as it's used for photosynthesis , it can maintain a steep concentration gradient
  • oxygen is produced by photyosynthesis , and diffused through spaces into open stomata (+ water vapour)
• Xylem + Phloem

  • they form vascular tissue of plant
  • xylem vessels + phloem sieve tubes
• Root hair cells

  • hair-like projections give it large surface area
  • mineral ions are actively transported from root hair cells, lowering water potential

  -> causing water to follow by osmosis, decreasing water potential

  • they have a special carrier protein to actively transport mineral ions
  • root hair cells provide ATP as it needs energy for active transport