The antenna ground plane will ideally be connected to the ground on the last active device in the transmitter, or the first active device in the receiver, chain. So if you have a transmitter with a power fet at the last stage, the source of the FET is attached with low inductance/resistance to the antenna ground plane.
Alternatively, you can hook the transmitter to a coaxial cable, and the coaxial cable has the center contact go to the monopole whip, and the ground shield go to the ground plane.
If you assume the negative is a good ground point, you are ignoring the various wire inductances and resistances in series.