Advanced Science Primary 5 Systems

A ring of stem is removed from a plant, removing the food-carrying tubes but leaving the water-carrying tubes intact. After a week, the stem above the cut swells. Why does this happen?

A Food made by the leaves cannot flow down and accumulates above the cut.
B The plant is storing extra water for survival.
C Mineral salts are trapped above the cut.
D Water cannot flow down to the roots and accumulates above the cut.
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Worked Solution

Step 1: The food-carrying tubes (phloem) transport food made in the leaves downwards to the rest of the plant. Step 2: Removing the outer ring removes these tubes. Step 3: Food cannot move past the cut, so it accumulates in the tissue just above it, causing swelling.

Correct answer: Food made by the leaves cannot flow down and accumulates above the cut.

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