RP2 - OSMOSIS ON PLANT TISSUE

• Osmosis

  Diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Effect of osmosis on plant tissue

  1. Place plant cell in water

  2. Water moves into cell by osmosis, cell expands

  3. Place plant cell in concentrated solution

  4. Water moves out of cell by osmosis, cell shrinks
• Potato

  • Commonly used plant tissue to investigate osmosis
  • Can also use other vegetables like beetroot or parsnip
• Investigating effect of osmosis on plant tissue

  1. Peel potato

  2. Use cork board to produce potato cylinders of same diameter

  3. Trim cylinders to same length (around 3cm)

  4. Measure length and mass of each cylinder

  5. Place cylinders in test tubes with different solutions (0.5M sugar, 2.5M sugar, distilled water)

  6. Leave overnight to allow osmosis

  7. Remove cylinders, gently roll on paper towel to remove surface moisture

  8. Measure length and mass of cylinders again
• Percentage change

  Calculated as: (change in value / original value) x 100
• Concentration of sugar solution

  Affects percentage change in mass or length of potato cylinder
• Required practical 2: Investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue


  1. Use a scalpel/cork borer to cut up a potato (remove peal) into 6 identical size onders

  2. Blot dry then measure initial mass of each

  3. Place each in a different concentration of sugar solution for 24 hours

  4. Blot potato dry with paper towel then measure final mass of each

  5. Percentage change in mass (change in mass/starting mass) x 100

  6. Repeat and calculate a mean for each concentration

  7. On a graph, plot % change in mass (y axis) against concentration of sugar solution (x axis)
• Independent variable


  Concentration of sugar solution
• Dependent variable


  Change in mass of plant tissue
• Control variables


  • Volume of solution
  • Temperature of solution
  • Time in solution
  • Starting size / length / shape of potato
  • Variety of potato
• Potato in [named solution] gained mass

  Gained water by osmosis through a partially permeable membrane as more dilute solution outside cells/cell contents are more concentrated than solution
• Potato in [named solution] didn't change mass

  No net gain/loss of water by osmosis as solution conc. inside cells = solution conc. outside cells