CAIE A Level Biology 9700 · Energy and respiration
Rice plants (Oryza sativa) are commonly cultivated in flooded paddy fields. The roots of rice are often submerged in waterlogged soil, where oxygen is scarce. Rice roots have two key adaptations that enable them to survive in these hypoxic conditions: the formation of aerenchyma in the root tissue, and the ability to carry out ethanol fermentation. Explain how each of these adaptations helps rice roots to tolerate waterlogged soils.
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.
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