Question

In an attempt to find out where a growing plant gets its mass, Van Helmont planted a willow seedling in a pot of soil. After five years, the willow weighed 76.8 kg, and the soil had lost 0.06 kg of weight. Only water had been added to the pot. Which of the following conclusions should Van Helmont have drawn?

• A. Plants get their mass from water
• B. Plants get their mass from water and air
• C. Plants get their mass from water and atmospheric $C{O}_2$
• D. Plants get all or almost all of their mass from a source other than soil

Answer 1

The correct option is D Plants get all or almost all of their mass from a source other than soil

Van Helmont carried out an experiment to see if the idea from ancient Greece was correct. He grew a willow tree in a weighed amount of soil. After five years, he discovered that the willow tree weighed about 74 kg more than it did at the start. As the weight of the soil had hardly changed, Van Helmont concluded that plant growth cannot only be due to minerals from the soil. He thought that the extra plant material had come from the water alone.

Therefore, the correct answer is option D.