Plant mineral requirementsEdexcel A-Level Biology A: Subtopic test

1. 1
   A grower produces tomatoes in a greenhouse using hydroponics, in which the roots grow in a nutrient solution rather than soil. The solution must contain every essential mineral ion. A batch of plants was accidentally given a solution that contained no nitrate ions.

   (a)

   Which molecule in the leaf cells of the tomato plants contains magnesium?

   [1 mark]

   • AGlucose
   • BStarch
   • CChlorophyll
   • DCellulose

   (b)

   The grower also checks the calcium ion concentration of the solution. Calcium ions are needed by the plants for the formation of which structure?

   [1 mark]

   • ACellulose microfibrils
   • BLignin in xylem walls
   • CStarch grains in chloroplasts
   • DThe middle lamella between neighbouring cell walls

   (c)

   The lower leaves of the plants given no nitrate turned yellow first, while the youngest leaves stayed green. Explain these observations.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A class investigates plant mineral deficiencies. Barley seedlings are grown for three weeks in four boiling tubes containing: a complete culture solution; a solution lacking nitrate; a solution lacking magnesium; and a solution lacking calcium. The same volume of solution is used in each tube and the tubes are kept in the same window.

   (a)

   What is the main reason for including the tube with the complete culture solution?

   [1 mark]

   • AIt acts as a control showing normal growth for comparison
   • BIt tests the effect of adding extra nitrate
   • CIt shows that the seedlings do not need minerals
   • DIt makes sure that the other tubes receive the same light

   (b)

   Air is bubbled through each solution. What is the main reason for this?

   [1 mark]

   • AThe roots need carbon dioxide for photosynthesis
   • BThe roots need oxygen for aerobic respiration to provide ATP for uptake of ions
   • CThe air keeps the ions dissolved in the solution
   • DThe air prevents the solution from getting too warm

   (c)

   The students wrapped each tube in black paper. Suggest why.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A pot plant with soft, non-woody stems is left without water for a week on a sunny windowsill. Its leaves and stems droop. After it is watered, it gradually becomes upright again.

   (a)

   Explain how water supports the stems of a non-woody plant such as this one.

   [3 marks]

   (b)

   Describe two roles of water in a plant, other than support, in photosynthesis and in transport.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A wheat farmer finds that some plants in a field have stunted growth and pale leaves. A soil test shows low concentrations of nitrate and magnesium ions. A student grows wheat seedlings for 21 days in four solutions and measures the mean dry mass of the seedlings: complete solution 4.8 g, solution lacking nitrate 1.9 g, solution lacking magnesium 3.1 g and solution lacking calcium 3.6 g. Each solution was tested on one group of seedlings.

   (a)

   Explain the importance of nitrate, calcium and magnesium ions to a plant and the symptoms of a deficiency of each.

   [6 marks]

   (b)

   Use the student's data to evaluate which mineral deficiency has the greatest effect on growth, and discuss the limitations of the investigation.

   [6 marks]

   Total for question 4: 12 marks

End of questions