GeorgeRocco12
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Q1. Plants need nitrate ions in order to make proteins
A plant is growing in soil flooded with water
Explain why the plant cannot absorb enough nitrate ions (5)

Q2 Plant roots absorb water mainly by osmosis
Plant roots absorb ions mainly by active transport

Explain why roots need to use the two different methods to absorb water and ions (4)
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macpatgh-Sheldon
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Q1. Even without flooding, the concentration of ions in the soil is low, i.e. the soil has a high water potential. If the soil is flooded, there are even less nitrate ions available in terms of concentration in the vicinity of the root hairs, so enough nitrate simply cannot be absorbed, even though the process involved is active transport.

Q2. The high water potential mentioned in Q1 means that water is easily absorbed by osmosis through the partly permeable membrane of the root hair epithelium. However, the concentrations of ions in the soil is low compared to that inside the root so absorption by diffusion is not an option. The absorption needs to occur against a conc-n gradient, so a mechanism is required that can use ATP to provide energy to drive the ions against this conc-n gradient = active transport.

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