大象传媒

Plant disease - OCR Gateway Growth of plants in different nutrient solutions

Pathogens are disease-causing viruses, bacteria, fungi or protists, which attack plants as well as animals. Plants have physical and chemical defences against pathogens.

Part of Biology (Single Science)Global challenges

Growth of plants in different nutrient solutions

When plants suffer from , they do not have enough ions. This can be investigated in science experiments by measuring the growth of barley seedlings.

Method:

  1. Sow ten barley seeds onto cotton wool in a petri dish. Add 10 cm3 of distilled water, seal using tape to avoid water loss through evaporation and place on a sunny windowsill to germinate. Repeat with three other petri dishes.
  2. About one week after germination, open each petri dish, pour out any distilled water and add 10 cm3 of the following solutions:
    • Petri dish 1 - Distilled water
    • Petri dish 2 - Culture solution containing magnesium sulfate and potassium nitrate
    • Petri dish 3 - Culture solution containing magnesium sulfate (deficient in nitrogen)
    • Petri dish 4 - Culture solution containing potassium nitrate (deficient in magnesium)
  3. Replace all petri dishes on the window sill and leave for two weeks.
  4. Open each petri dish and carefully remove each from the cotton wool.
  5. Dry in an oven and record the total dry mass of each set of ten seedlings.

Results:

Petri dishSolution addedSeedling dry mass
1Distilled water2.1 g
2Culture solution containing magnesium sulfate and potassium nitrate3.4 g
3Culture solution containing magnesium sulfate (deficient in nitrogen)2.3 g
4Culture solution containing potassium nitrate (deficient in magnesium)2.7 g
Petri dish1
Solution addedDistilled water
Seedling dry mass2.1 g
Petri dish2
Solution addedCulture solution containing magnesium sulfate and potassium nitrate
Seedling dry mass3.4 g
Petri dish3
Solution addedCulture solution containing magnesium sulfate (deficient in nitrogen)
Seedling dry mass2.3 g
Petri dish4
Solution addedCulture solution containing potassium nitrate (deficient in magnesium)
Seedling dry mass2.7 g

Conclusions:

Question

What conclusions can you draw from this data? Use numbers in your answer. [4 marks]