Fig. 1 shows a cross-section through a young sunflower stem viewed using a microscope. The dark ring contains transport tissue. A gardener damaged the outer...
Question 1 Report
Fig. 1 shows a cross-section through a young sunflower stem viewed using a microscope. The dark ring contains transport tissue. A gardener damaged the outer surface on one side of similar stems while tying them to canes. Several days later, sugars built up above the damaged region but water still reached the leaves.
(a) Name the tissue that transports water from roots to a leaf. [1]
(b) Use the gardener's observation to identify the tissue that was damaged. [1]
(c) Describe the transport of sucrose in this tissue. [1]
(d) Explain why damage to this tissue can reduce growth in roots below the damaged region. [2]
Answer Details
(a) The tissue that transports water from roots to leaves is xylem. [1]
(b) The damaged tissue was phloem. Sugars accumulated above the damage, showing that their transport pathway had been interrupted, while water still reached the leaves through intact xylem. [1]
(c) Phloem transports sucrose from leaves to other parts of the plant. This movement is called translocation. [1]
(d) Roots below the damaged region receive less sucrose. They therefore have less substrate for respiration, so less energy is released for growth. [2]
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