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Adrian decided to conduct an experiment on the effects of gibberellins on plant growth for a science project.. He grew a dwarf type of garden pea and sprayed half of plants with gibberellin every day for 3 weeks after germination. The other half of the plants were not sprayed. At the end of his experiment, he measured the height of all of the plants. The dwarf plants that were sprayed with gibberellin were much taller than the unsprayed plants. He concluded that gibberellin increases the growth rate of pea plants. How could you modify Adrian's conclusion to make it better reflect the results he obtained? How could Adrian have designed his experiment differently to make it a better experiment?

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Conclusion: Spraying dwarf plants with gibberellins increases the possibility that they would grow taller than dwarf plants not sprayed with gibberellins. Note: he should not include all pea plants because he used only dwarf pea plants.

Change to experiment: Spray the control plants with the solution minus the gibberellin. Include another experimental group and control group with tall pea plants.
Reply:A negative control should have been included. Whatever is in the solution containing the gibberellin (but not containing the gibberlellin itself) should havbe been sprayed on a third set of plants. This will exclude (or include) that another factor has contributed to the growth of the plants..



To better reflect the results, Adrian could conclude that gibberellins increases longitudinal growth of the stalk of the pea plants (since "bushiness" was not a factor).