Alternative to pratical

Question 1

The higher the concentration of the solution

Answer 1

The further the avid diffuses into the agar

Question 2

Describe the appearance of the onion cells in distilled water

Answer 2

The cells in distilled water ahve a large, pink or purple vacuole. The cytoplasm is not visible as it is pressed against the cell wall by the vacuole. The cells are turgid

Question 3

Describe the appearance of the onion cells in a salt solution

Answer 3

The cells in the 5% salt solution have a vacuole that has decreased in size (it is a lot smaller ). The cells are now flaccid or even plasmolysed (if the cytoplasm has detached from the cell wall).
The colour in the vacuole is more intense / darker

Question 4

Explain the change in appearance you observed after having replaced the distilled water with 5% salt solution

Answer 4

When placed in the 5% salt solution, the vacuole became smaller. So, the cell lost water. The salt solution has lower water potential than the inside of the cell. Osmosis took place and water left the cells (the vacuole) down its water potential gradient (from a high water potential to a low water potential) the cells are now flaccid or plasmolysed.