Running PEX line through PVC then thread into end
One way would be to run your pex cable up the PVC pipe and put a PEX/ female hose connector on the end of the pex. (see below)

Another alternative would be to connect the pex to your PVC pipe at the bottom with this type of connector

and then at the top of the PVC pipe connect a female hose fitting

Your PC pipe would actually be under pressure at this point.
These fittings are available at home stores and plumbing supply stores.