To Determine Where Plants Obtain the Raw Materials Needed for Growth

Essay

To determine where plants obtain the raw materials needed for growth, van Helmont collected data on the growth of a willow tree for over 5 years. He measured the amount of soil in a pot, planted the tree in the soil, and then watered the tree with rainwater. After 5 years, he weighed the soil and the tree. He concluded that the tree did not gain its mass from the soil, but incorrectly concluded that the tree had gained its mass from the water. What are two critical problems with this study design? How could you redesign the study to fix these two study design problems?