The Poser 4 render engine does not support ray-tracing, which is needed for true reflections. Poser 5 (and above), Vue, Lightwave, and Studio Max all support ray-traced reflections.

There are a few cheats for Poser 4: I explain some of them on my website: How to Make Reflections (in Poser 4).
I also have a tutorial on How to Make Reflections in Poser 5 (and Above) and How to Make Realistic Poser Image Using Reflection Maps (which uses the Reflect node).

VanishingPoint... Advanced 3D Modeling Solutions