A student prepares two epidermal tissue strips from a purple onion (Allium cepa). She submerges one strip in a dilute 0.1 mol/dm3 NaCl0.1\text{ mol/dm}^3\text{ NaCl}0.1 mol/dm3 NaCl solution and the second strip in a concentrated 1.5 mol/dm3 NaCl1.5\text{ mol/dm}^3\text{ NaCl}1.5 mol/dm3 NaCl solution. After 15 minutes, she observes the cells under a light microscope and records the images shown below:
Suggest why purple onion epidermal cells are particularly useful for demonstrating these physical changes without the use of chemical stains.
Explain what is meant by the term osmosis.
Explain the differences in the appearance of the onion cells between the two NaCl concentrations.
When human red blood cells are placed in a very dilute salt solution, they swell and burst. Explain why this occurs in red blood cells but does not happen to the onion epidermal cells.