Jan Baptista van Helmont did an important experiment related to photosynthesis. He weighed a small willow tree and a pot of soil. Jan then planted the tree in the pot. Over the course of five years, he added only water to the pot. At the end of five years, he weighed the tree and found that it had gained 74.4 kg. He weighed the soil, and it was only 57 g less. What do the results of this specific experiment demonstrate about what is needed for a plant to grow and increase its mass?

Question

A.  All of the food a plant needs to grow comes from the soil
B.  Plants do not need soil to grow
C.  Plants must be able to increase their mass using substances in addition to what is found in soil
D.  All of the food a plant needs to grow comes from the water
E.  Plants need oxygen to grow

Answer 1

C.  Plants must be able to increase their mass using substances in addition to what is found in soil

Because the plant increased its mass to a greater extent than the soil mass was depleted, this suggests that the plant can increase its mass using substances other than what is found in the soil.