Suppose that a botanist is interested in the effect of light on plants. In an experiment she conducts, 50 individual plants of a single species of flowering plant are grown for 60 days under different lengths of artificial daylight in a greenhouse. The plant species has flowers that can be either white or pink, depending on the genetics of the parent plants. The amount of water and fertilizer provided to each plant is constant. At the end of the experiment, the size of each leaf of every plant is measured. The independent variable in this experiment is the Group of answer choices leaf's size. duration of artificial daylight. flower's color. duration of the experiment.

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.