Light intensity and temperature can act as limiting factors in the rate of transpiration by affecting stomatal opening. Explain what is meant by a limiting factor.
An investigation was carried out into the effect of soil salinity (sodium chloride, NaCl\text{NaCl}NaCl, concentration) on the survival of young barley seedlings (Hordeum vulgare\textit{Hordeum vulgare}Hordeum vulgare). Each experimental group initially contained 60 seedlings.
The results are shown in the table below:
| Salinity (mmol dm−3\text{mmol dm}^{-3}mmol dm−3) | Day | Number of seedlings surviving |
|---|---|---|
| 20 | 5 | 60 |
| 10 | 60 | |
| 15 | 59 | |
| 20 | 59 | |
| 25 | 58 | |
| 100 | 5 | 60 |
| 10 | 57 | |
| 15 | 55 | |
| 20 | 53 | |
| 25 | 50 | |
| 400 | 5 | 60 |
| 10 | 45 | |
| 15 | 32 | |
| 20 | 18 | |
| 25 | 5 |
Summarise the conclusions that can be drawn from these data.
Explain how extremely high soil salinity can lead to dehydration and seedling death, referring to water potential and osmosis.
Soluble magnesium (Mg2+\text{Mg}^{2+}Mg2+) ions are actively transported into root hair cells.
Explain why water molecules can form electrostatic interactions with magnesium (Mg2+\text{Mg}^{2+}Mg2+) ions.
Describe how the active transport of ions across a plant cell membrane causes water to enter the cell.
