Final answer:
In the described scenario, the growth rate or size of the plant is the dependent variable, and the amount of sunlight is the independent variable that is manipulated in the experiment.
Step-by-step explanation:
In the scenario described, the dependent variable is the growth rate or size of the plant, which is the variable that is expected to change as a result of manipulating the independent variable.
The independent variable, although not directly asked in this query, is the amount of sunlight the plants receive. This is the variable that is changed or controlled by the researcher to test its effects on plant growth.
To study the effect of sunlight on plant growth, one must ensure that other variables that could influence the outcome, like water, soil quality, and temperature, are kept constant across all subjects in the experiment.