  A Choquet-type integral representation result for non-negative subharmonic
functions of a one-dimensional regular diffusion is established. The
representation allows in particular an integral equation for strictly positive
subharmonic functions that is driven by the Revuz measure of the associated
continuous additive functional. Moreover, via the aforementioned integral
equation, one can construct an {\em \Ito-Watanabe pair} $(g,A)$ that consist of
a subharmonic function $g$ and a continuous additive functional $A$ is with
Revuz measure $\mu_A$ such that $g(X)\exp(-A)$ is a local martingale. Changes
of measures associated with \Ito-Watanabe pairs are studied and shown to modify
the long term behaviour of the original diffusion process to exhibit
transience.
