Disable reflection of some objects

Hello. Probably my problem has been discussed in many forums. Let me explain my problem. I have three balls with mirror material. Then I added a white plane above them to give more depth. I would like it to be reflected in the spheres only the floor, instead spheres reflect each other. I read that you need to create two scenes or distributing objects at various levels. Thanks in advance.

That can be done. Using Blender Internal you can set a material to be ‘Traceable’ which allows it to participate in reflections and other ray trace algorithms. In Cycles there is a Ray Visibility panel, located under the object, to control what parts of a material are considered ‘Traceable’.

Thank you. But now, how I exclude the shadows produced by the balls?