An early experiment by Van Helmont (1600s) describes how he "grew a tree in a large pot and found that after five years, the amo
unt of soil in the pot had not changed. He concluded that the increase in weight was due to the addition of water." At that time, the compounds in the air had not yet been identified. Today, you know that he only discovered half the story. Which additional experiment would provide evidence for the rest of the story? A. A very careful audit of the water taken in and lost by the tree would have revealed only half the added weight gained by the tree.
B. Carbon is discovered as a major element in trees and is lacking in water molecules.
C. Radioactive carbon in CO2 in the air is soon located as part of tree structures.
D. The critical experiment involves the conversion of nutrients in the soil.
E. All but the nutrient conversion is correct.
