The independent variable in an experiment is the variable that influences the other variable called the dependent variable. The independent variable is therefore manipulated to ascertain its effect on the dependent variable.
Explanation:
In this experiment, the air temperature is the independent variable because it is being manipulated to check its effect on the plant's photosynthesis. Probably, the higher the air temperatures, the higher the rate of photosynthesis and vice versa. The rate of photosynthesis is the dependent variable and is what is being measured as the air temperature is being controlled.
