Name the microscope type that was used to produce the image in Fig. 1.1.
Calculate the true length, in micrometres ($\mu\text{m}$), of the root hair cell labelled in Fig. 1.1. Use the image length of the root hair cell measured along line X-Y in your calculation.
Root hairs are key adaptations of root hair cells for taking up water. Explain one way in which root hairs adapt root hair cells for water uptake.
Mineral ions are absorbed by root hair cells. Table 1.1 gives the concentrations of sodium ions ($\text{Na}^+$) and potassium ions ($\text{K}^+$) inside the root hair cells of a plant root and in the surrounding soil solution. Using Table 1.1, suggest the transport mechanisms for the movement of $\text{Na}^+$ and $\text{K}^+$ from the soil solution into the root hair cells, and state the reasons for your suggestions.
The tissue layer between the outer root surface and the endodermis is called the cortex. Table 1.2 gives the water potential of two neighbouring cells, A and B, in the cortex of a root. Using Table 1.2, explain the direction in which water moves between cell A and cell B.
In some soils, small negatively charged clay particles bind positive ions such as iron ions ($\text{Fe}^{2+}$). Fig. 1.2 shows the findings of one investigation into how pH affects the concentration of free $\text{Fe}^{2+}$ available in soil solution for absorption by root hair cells. Using Fig. 1.2, suggest and explain how the carbon dioxide released during respiration of root hair cells can raise the concentration of free $\text{Fe}^{2+}$ available for absorption by root hair cells.
Dissolved $\text{Fe}^{2+}$ is moved through the root tissues to the xylem. When the amount of dissolved $\text{Fe}^{2+}$ taken up by root hair cells is greater than the plant needs, not all of the $\text{Fe}^{2+}$ absorbed is delivered to the xylem. Suggest how the endodermis can lower the amount of $\text{Fe}^{2+}$ reaching the xylem.
Dissolved $\text{Fe}^{2+}$ is carried across root tissues to the xylem. If the amount of dissolved $\text{Fe}^{2+}$ absorbed by root hair cells is greater than the plant requires, not all of the $\text{Fe}^{2+}$ absorbed will be moved to the xylem. Suggest how the endodermis can reduce the amount of $\text{Fe}^{2+}$ reaching the xylem.