This is because the traits like height, are influenced by environmental conditions around the individual. For example, there are two children born to same mother. But one is given best facilities, nutrition and care, whereas other one is brought up by a poor family, which hardly get good food to eat. His condition is much worse than the first case. In such a situation, the former child will grow up healthy and fit, and will have more height than the later one. Although, both got genes from same parent, but the environmental conditions influenced the expression of those genes differently.
Adenine, Guanine, Cytosine, Thymine?
Scientific method includes some steps that are necessary for conducting the successful experiment.
1. Make an observation
You observe the growth of the plant under the influence of light (phototropic effect) and you notice that some plants successfully grow under artificial light. You want to compare that growth with growth under the sunlight.
2. Ask a question
How does the light influence plant growth?
Are the wavelengths of the light important?
Is natural light source (sun) better for plant growth...
3. Form a hypothesis - it is a testable potential answer to the question
For example: Sunlight induces higher phototropic reaction.
4. Make a prediction
Sunlight is richer in red and blue hues which are both extremely important to plant growth.
5. Test the prediction
Design an experiment by putting one pot with beans outside on sunlight and other under the light bulb. Other conditions such as water must be the same. Monitor their growth for about 2 weeks and measure the results.
6. Analyze the data and make a conclusion.