Carbon dioxide concentration and light intensity can act as limiting factors in photosynthesis. Explain what is meant by a limiting factor.
An investigation was carried out into the effect of soil nitrate ion (NO3−\text{NO}_3^-NO3−) concentration on the survival of young wheat shoots. Each experimental group initially contained 80 shoots.
The results are shown in the table below:
| Nitrate concentration (mg dm−3\text{mg dm}^{-3}mg dm−3) | Day | Number of shoots surviving |
|---|---|---|
| 5 | 4 | 80 |
| 8 | 79 | |
| 12 | 78 | |
| 16 | 77 | |
| 20 | 76 | |
| 25 | 4 | 80 |
| 8 | 78 | |
| 12 | 75 | |
| 16 | 74 | |
| 20 | 72 | |
| 100 | 4 | 80 |
| 8 | 65 | |
| 12 | 52 | |
| 16 | 40 | |
| 20 | 28 |
Summarise the conclusions that can be drawn from these data.
Explain how extremely high soil nitrate concentrations can lead to dehydration and shoot death, referring to water potential and osmosis.
Soluble potassium (K+\text{K}^+K+) ions are actively transported into root hair cells.
Explain why water molecules can form electrostatic interactions with potassium (K+\text{K}^+K+) ions.
Describe how the active transport of ions across a plant cell membrane causes water to enter the cell.
