An experiment is set up to determine if wheat grows better when it is planted by itself or together with clover. The setup involves 3 pans of each treatment. Set-up A, B and C contain wheat alone. Set-ups D, E and F contain clover and wheat planted together, in rows alternating one seed of each type. One hundred seeds are planted in each pan. all treatments contain the same type of soil, are planted in the same size of pan, are exposed to the same amount of sunlight, and are maintained at the same temperature throughout the course of the experiment. Use Passage 1-1. Constants in this experiment are: