An experiment was carried out to investigate the effect of gibberellic acid (GA) on the growth of dwarf pea plants. GA can be absorbed by leaves. 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 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 (1)
2.4.1 Hypothesis: A possible hypothesis for this investigation could be: "Increasing the mass of gibberellic acid (GA) applied to the leaves of dwarf pea plants will result in a greater percentage increase in their stem height."
2.4.2 Two Controlled Variables:
Temperature : The temperature at which the plants are kept should be controlled because temperature can affect plant growth and the effectiveness of gibberellic acid.
Type of Soil : The type of soil used in each pot should be identical and consistent because different soil types can have varying nutrient levels and water retention capabilities that might impact the plant growth.
2.4.3 Increase in Number of Plants: An increase in the number of plants used in the investigation would likely lead to more reliable and accurate results. Having a larger sample size helps to ensure that the results are not due to random variation or anomalies in the experimental conditions. It increases the likelihood that the results are representative of the general effect of GA on dwarf pea plant growth.
2.4.4 Use of Gibberellins in Agriculture: Gibberellins, like gibberellic acid, are used in agriculture to improve fruit development by promoting cell division and elongation. As a result, these hormones can help increase fruit size and weight. Additionally, gibberellins can help in synchronizing fruit ripening and improving the yield and quality of fruits by ensuring that they develop under optimal growth conditions. This is particularly beneficial for commercial growers aiming to improve crop productivity and presentation. Gibberellins are also used to break seed dormancy, enhance germination rates, and initiate flowering in plants that otherwise may not flower under specific conditions.
