Answer:
Duration of artificial daylight.
Step-by-step explanation:
- A variable used in an experiment that is not affected by other variables and at the same time determines the value of other variables is termed as the independent variable.
- In a particular experiment the independent variable is the one that can only be controlled or manipulated by the person who is carrying out the experiment.
- In the given situation, the amount of water and fertiliser is constant and not changed by the experimenter however, it is the length of the artificial daylight that is being changed by the experimenter and the size of the leaf of the plant is being measured in response to the duration of the artificial daylight.
- Hence, the duration of the artificial daylight is the independent variable used in the experiment.