Hypothesis: The macronutrients nitrogen, phosphorus and potassium are important for the healthy and normal growth of plants.
Variables:
(a) manipulated variable : contents of the culture solution
(b) responding variables : growth of plant and colour and size of leaves
(c) fixed variables : size and type of seedlings, volume of culture solution
Materials:
Cotton wool, black paper, glass tube, rubber tube, distilled water, maize seedling, calcium nitrate, potassium nitrate, potassium dihydrogen phosphate, magnesium sulphate, ferum phosphate, calcium chloride, potassium chloride, sodium nitrate and calcium dihydrogen phosphate.
Apparatus:
Bottle, measuring cylinder and weighing machine.
Procedure :
1 Four bottles are labelled A to D.
2 Each bottle is filled with a culture solution as shown in the table below.
3 Each bottle is fitted with a cork carrying a maize seedling and a glass tube as shown in Figure 2.10.
4 Each bottle is wrapped with a piece of black paper and placed near a window in the science laboratory where there is sunlight for 4-5 weeks.
5 The bottles are aerated each day.
6 The culture solution in each bottle is replaced each week.
7 The seedlings are observed each week and the observations are recorded.
Results :
Discussion:
1 Bottle A contains a complete culture solution with all the macronutrients and micronutrients required. The seedling shows normal and healthy growth.
2 Bottle A is set up as a control for comparison.
3 The bottles are covered with black paper to prevent sunlight from reaching the solution because sunlight encourages the growth of algae. The algae would absorb the nutrients, thus affecting the experiment.
4 The seedlings used must be of the same size (same age).
5 The bottles are aerated by blowing air through the rubber and glass tubes to supply oxygen for respiration.
6 The solutions are replaced each week to replace the minerals absorbed by the seedlings.
Conclusion:
The seedling in the complete culture solution grows into a healthy and normal plant.
The lack of a particular nutrient affects the growth of a plant as well as the colour and size of its leaves.
Thus, the hypothesis can be accepted.
Effects of the deficiency of nitrogen, phosphorus and potassium on plants ;
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