An agricultural research institute is developing automated vertical farming systems to optimize the cultivation of butterhead lettuce (Lactuca sativa).
In one experiment, scientists compared growth in a standard aerated nutrient solution containing all essential macronutrients with a solution depleted of nitrogen.
Explain why the nutrient solution must be continuously aerated with oxygen gas.
The root chambers in this vertical farm are constructed from opaque black polymer. Suggest why blocking all light from the root chambers is necessary for a valid investigation.
Nitrogen is a key constituent of the green pigment required for photosynthesis. State the name of this pigment and describe the physical appearance of the lettuce leaves when grown in the nitrogen-deficient solution.
State two abiotic factors, other than nutrient availability and root aeration, that must be kept identical for both sets of plants during their growth.
Runoff of nitrogen-rich agricultural wastewater from such intensive farms into nearby slow-flowing river channels can lead to severe ecological damage.
Explain how the discharge of highly soluble nitrates into a river ecosystem can lead to the death of active aquatic organisms such as trout.
44 exam-style questions on Edexcel IGCSE Biology Human influences on the environment. Each one has a worked solution and a mark scheme showing where the marks go.