Question

Write a note on Van Helmont’s experiment focussing on how he concluded that water was important for plant growth and increase in body mass.

Answer 1

In 1634, Jan Baptist van Helmont was arrested by agents of the Spanish Inquisition for the crime of studying plants and other phenomena. While under house arrest, he started to consider how plants grew. 

The prevailing theory at the time was that plants grew by eating soil, and van Helmont devised a clever investigation to test this idea. He weighed a willow tree and weighed dry soil. He planted the tree, watered it and then left it for 5 years. He then re-weighed the tree, which had increased in mass by over 12 stone. He dried the soil and weighed it, showing that the soil was almost the same mass. He concluded that the tree grew by drinking water.

Answer 2

Van Helmont

Explanation:

• Van Helmont’s well known “willow tree experiment” was performed over a five-year time period in the 1630s
• The prevailing common theory at the time was that plants grew by eating and digesting the soil, but Van Helmont disagreed, and constructed an experiment to test this
• In this experiment, he planted a willow tree in a pot with soil and placed in a controlled environment
• He weighed the mass of the soil in the pot and carefully watered the willow tree over the next five years
• At the end of his experiment Van Helmont removed the tree from the soil, weighed it, and weighed the dry pot of soil
• The soil had barely changed in weight
• Following this finding, Van Helmont came to the conclusion that the willow tree growth was in turn from the water and not the soil
• We now know his findings were generally inaccurate; however, they did prove that water was a contributing factor to the growth of plants, and that plants did not “eat” or “digest” soil