These eight original questions follow the lessons in plant nutrition. They ramp in difficulty and each answer shows the reasoning.
Write your answer first, then open the answer box.
The questions
Question 1. State one use of nitrate in a plant.
Answer
Nitrate is used to make amino acids, which are joined to form proteins. It is also needed for chlorophyll.
Question 2. Explain why magnesium is needed for photosynthesis.
Answer
Magnesium is part of the chlorophyll molecule. Without it, less chlorophyll is made, so less light energy is absorbed.
Question 3. Why do root hair cells take in mineral ions by active transport?
Answer
The concentration of ions can be higher inside the root hair cell than in the soil. Active transport moves ions against the gradient, using energy from respiration.
Question 4. Seedlings in a solution without phosphate grew 5.0 cm, and those in a complete solution grew 12.0 cm. Suggest why the complete solution is included.
Answer
It is the control. It shows normal growth, so the loss caused by missing phosphate can be measured: 12.0 − 5.0 = 7.0 cm.
Question 5. The older leaves of a plant turn yellow and its growth is slow. Suggest a likely missing mineral and give one piece of evidence you would want.
Answer
Nitrate is a likely cause, as it is needed for proteins and chlorophyll and can move to new growth. Evidence wanted: a control plant in a complete solution, and a comparison of height gain and leaf colour.
Question 6. Explain why a pitcher plant that traps insects still has green leaves.
Answer
The plant makes its own sugars by photosynthesis, which needs chlorophyll. The insects supply nitrogen compounds that the poor soil lacks, not sugars.
Question 7. State one benefit to a legume and one to the bacteria in its root nodules.
Answer
The legume gains nitrogen compounds made from nitrogen in the air. The bacteria gain shelter and sugars from the plant.
Question 8. Plan a fair test of whether potassium affects leaf growth. State the changed, measured and two constant variables.
Answer
Changed: potassium in the solution (with or without). Measured: leaf area or number of leaves after a set time. Constant, any two of: type and age of plant, volume of solution, light, temperature and other minerals. Include a control with all minerals and use at least five plants per group.
If you got these wrong
Questions 1 to 3 belong to explaining why plants need mineral ions. Questions 4 and 5 belong to interpreting mineral deficiency evidence.
Questions 6 and 7 need comparing nutritional adaptations, and question 8 needs planning a fair plant nutrition investigation. Log slips in the mistake log tool.
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