What is the use of stem of a tuning fork?

A tuning fork A,marked 512 Hz, produces 5 beats per second,when sounded with another unmarked tuning fork B.If B is loaded with wax the number of beats is again 5 per second.What is the frequency of the tuning fork B when not loaded?

What is the function of a stem in a plant ?

How can the frequency of a tuning fork be changed?