Life would not be possible without plants. Plants supply food to many organisms (including people), produce oxygen, absorb carbon dioxide from the air, provide products for human use, and homes for many other living things. It is not surprising, therefore, that plant growth is a familiar topic in the primary school science curriculum. This paper…

Three and a half centuries ago, a five-year experiment was conducted involving the growth of a willow tree in a pot which received only water. The conclusion, that a tree is therefore made solely from water, was not so ridiculous when there was still general acceptance of the Aristotelian view of only four "elements": water, earth, fire and air.…