The experiment investigates the effect of gibberellic acid (GA) on the growth of dwarf pea plants. Six identical pea plants were planted in pots containing 100 g of soil. The leaves of each plant were sprayed with equal volumes of water containing different masses of GA. The soil in each pot received 20 cm³ water each day, and the plants were continuously exposed to equal light intensity from above.
After seven days, the stem height of each plant was measured, and the percentage increase in stem heights was calculated.
The results of the experiment are shown in the table below:
| Mass of GA applied (micrograms) | Percentage increase in stem height (%) |
|---|---|
| 0.01 | 90 |
| 0.03 | 120 |
| 0.05 | 160 |
| 0.08 | 240 |
| 0.10 | 320 |
| 0.11 | 350 |
2.4.1 State a hypothesis for this investigation.
2.4.2 Identify TWO variables, not already mentioned, that should have been controlled to ensure the experimental procedure was valid.
2.4.3 How will an increase in the number of plants used in this investigation influence the results?
2.4.4 Explain the use of gibberellins in agriculture to improve fruit development.
Answer (2)
2.4.1 State a hypothesis for this investigation.
A suitable hypothesis for this experiment could be: "Increasing the mass of gibberellic acid (GA) will result in a greater percentage increase in the stem height of dwarf pea plants."
2.4.2 Identify TWO variables, not already mentioned, that should have been controlled to ensure the experimental procedure was valid.
Temperature : Ensuring that all plants are kept at the same temperature throughout the experiment is crucial, as temperature can significantly affect plant growth and development.
Humidity : Consistent humidity levels should be maintained for all plants, as variations in humidity can influence the transpiration rate and overall growth of the plants.
2.4.3 How will an increase in the number of plants used in this investigation influence the results?
Increasing the number of plants in the experiment can improve the reliability and accuracy of the results. With a larger sample size, the impact of anomalies or outliers is minimized, allowing for a better average result and greater confidence in the conclusions drawn from the data.
2.4.4 Explain the use of gibberellins in agriculture to improve fruit development.
Gibberellins, such as gibberellic acid, are plant hormones widely used in agriculture to promote growth and improve fruit development. They play a crucial role by:
Promoting Cell Elongation : Gibberellins stimulate cell elongation, which enhances the growth of fruit and increases its size.
Breaking Dormancy : These hormones help in breaking seed and bud dormancy, leading to enhanced flowering and fruit set.
Improving Fruit Shape and Quality : By regulating growth processes, gibberellins can improve the uniformity and quality of fruits, making them more marketable.
Enhancing Yields : Using gibberellins effectively can increase the overall yield and productivity of fruit crops by ensuring better pollination and fruit setting.
The hypothesis suggests that increasing gibberellic acid will lead to greater stem height increases in dwarf pea plants. Controlled variables such as soil type and light duration are necessary for valid results. Gibberellins, like gibberellic acid, are used in agriculture to promote growth, improve fruit shape and yields, and break seed dormancy.
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