need some background on plant and develop a hypothesis?

Question

my son has to science project on plants and this is the question do some background reseach and develop a hypothesis

Answer 1

How about an experiment to see whether talking to a house plant really stimulates its growth. Is it the words or is it the carbon dioxide from his breath?

You need two sets of plants that are identical. You need one to be exposed (by loudspeaker) to the sound of his words and the other to have him up close and breathing on it while talking.