Salvinia minima (water spangles) is a floating freshwater fern that grows by producing new leaves called fronds. Many mineral ions are required for healthy plant growth.
State one specific mineral ion required by plants for healthy growth, and describe its role in plant biochemistry.
Copper ions (Cu2+\text{Cu}^{2+}Cu2+) can inhibit the growth of Salvinia minima. To investigate this, a student set up two containers:
The student counted the number of living fronds every three days. The table below shows her results:
| Day | Container X (with copper ions) | Container Y (without copper ions) |
|---|---|---|
| 0 | 16 | 16 |
| 3 | 16 | 20 |
| 6 | 15 | 28 |
| 9 | 10 | 44 |
| 12 | 5 | 68 |
| 15 | 0 | 92 |
Calculate the percentage increase in the number of living fronds in Container Y from Day 0 to Day 15. Show your working.
State three environmental or experimental variables, other than the volume and concentration of the nutrient solution, that must be controlled to ensure the results are valid.
