A student investigated the movement of a fungal pathogen through plant stem tissue.
The student cut ten equal-sized cubes from the same plant stem. In five cubes, the cell walls were not deliberately damaged. The other five cubes were pierced many times with a fine needle to break many cell walls, without changing the size of the cubes.
The same amount of the fungus was placed in the centre of each cube. All the cubes were kept under the same conditions for 3 days.
| Treatment of tissue | Mean distance spread by the fungus / mm |
|---|---|
| cell walls not deliberately damaged | 2.4 |
| many cell walls broken | 6.8 |
(i) State which treatment allowed the fungus to spread further.
(ii) Calculate how much further, on average, the fungus spread in this treatment.
Explain how the cellulose cell walls reduced the spread of the fungus through the tissue.
Another student plans to use 10 mm wide cubes for one treatment and 15 mm wide cubes for the other treatment.
State the variable that would not be controlled.
A deep cut was accidentally made along one cube in the group whose cell walls were not deliberately damaged.
Suggest why the fungus could spread further through this cube than through the other cubes in the same group.
82 exam-style questions on Edexcel GCSE Biology 5.2 Plant and body defences, covering 5.2.1 Physical plant defences, 5.2.2 Chemical plant defences, 5.2.3 Detecting plant diseases, and 5.2.4 Human physical and chemical defences. Each one has a worked solution and a mark scheme showing where the marks go.