The transport of water from the soil solution to the xylem of roots occurs by the apoplast and symplast pathways. Mineral ions can be transported dissolved in water. Researchers investigated the mechanism of transport used for the uptake of potassium ions $$$\left(\mathrm{K}^{+}\right)$$$into root epidermal cells at different concentrations of $$$\mathrm{K}^{+}$$$in the soil solution. Complete Table 6.1 to provide information about the two different transport mechanisms that were identified by the researchers. Table 6.1

Biology

IGCSE&ALevel

CAIE

Exam No：9700_w24_qp_22 Year：2024 Question No：6(b)

Answer:

Knowledge points:

7.2.1 state that some mineral ions and organic compounds can be transported within plants dissolved in water

7.2.2.1 apoplast pathway, including reference to lignin and cellulose

7.2.2.2 symplast pathway, including reference to the endodermis, Casparian strip and suberin

7.2.3 explain that transpiration involves the evaporation of water from the internal surfaces of leaves followed by diffusion of water vapour to the atmosphere

7.2.4 explain how hydrogen bonding of water molecules is involved with movement of water in the xylem by cohesion-tension in transpiration pull and by adhesion to cellulose in cell walls

7.2.5 make annotated drawings of transverse sections of leaves from xerophytic plants to explain how they are adapted to reduce water loss by transpiration

7.2.6 state that assimilates dissolved in water, such as sucrose and amino acids, move from sources to sinks in phloem sieve tubes

7.2.7 explain how companion cells transfer assimilates to phloem sieve tubes, with reference to proton pumps and cotransporter proteins

7.2.8 explain mass flow in phloem sieve tubes down a hydrostatic pressure gradient from source to sink

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Knowledge points:

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