What is wrong with my triMesh

I am trying to create a earth with several triMesh, each triMesh had been set TextureState and BlendState, but the result turn out to be a strange case : the front and back texture seem overlap, so I could not realize what is going on with these triMesh. I am still junior about jme, so can somebody kindly help me to check it out ?

you can refer to the attached picture :

maybe it is a stupid question, and I have found it out, it is becaused I haven`t set bounding volumes for each triMesh, just for your reference