CAIE A Level Biology 9700 · Transport in plants
A student investigates water uptake in a plant root. They place a root in a dilute solution of a water-soluble dye. They observe that the dye moves through the cell walls of the outer root tissues but is stopped at a band of cells around the stele. However, water continues to move into the xylem. Explain how water moves from the soil to the xylem in the root, comparing the apoplast and symplast pathways.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.