Researchers transfer young seedlings from water into two samples of the same concentrated mineral-salt solution. The samples are kept at different oxygen concentrations.
The nitrate ion concentration in each sample remains lower than the nitrate ion concentration inside the root hair cells.
The researchers record the percentage of root hair cells that are plasmolysed.
| Treatment | Oxygen concentration in solution (mg dm−3^{-3}−3) | Cells plasmolysed after 1 hour (%) | Cells plasmolysed after 8 hours (%) |
|---|---|---|---|
| A | 8.0 | 74 | 19 |
| B | 0.0 | 72 | 70 |
Explain why a high percentage of the root hair cells are plasmolysed after 1 hour in both treatments.
Suggest why the percentage of plasmolysed cells falls much more in treatment A than in treatment B after 8 hours.
194 exam-style questions on OCR GCSE Biology 2.1 Supplying the cell, covering 2.1.1 Transport across cell membranes, 2.1.2 Mitosis and the cell cycle, 2.1.3 Importance of cell differentiation, and 2.1.4 Stem cells. Each one has a worked solution and a mark scheme showing where the marks go.