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?