Standard Science Primary 5 Systems

Mei removed the outer ring of the stem of a plant, cutting away the food-carrying tubes but leaving the water-carrying tubes intact. After a week, a swelling was observed just ABOVE the cut. Why did the swelling occur?

A The stem absorbed extra water from the surrounding air.
B The cut allowed bacteria to enter and cause an infection.
C Food made by the leaves could not be transported past the cut.
D Water from the roots was trapped above the cut.
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Worked Solution

Step 1: Leaves make food during photosynthesis. Step 2: Food is transported downwards via the food-carrying tubes (phloem) which are on the outer edge of the stem. Step 3: Since the tubes are cut, the food cannot travel down and accumulates above the cut, causing it to swell.

Correct answer: Food made by the leaves could not be transported past the cut.

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