I did not get to create beautiful trees. One can see the illuminated plane, how to get rid of the lighting? What would a uniform illumination of the object. Big Picture rF2, small rF1.
Set the tree's normal as "Pointy" in the Max Plugin. If you use either "gmotor normals" or "max normals" you'll get the bad effect shown in the pictures. Pointy normals will force the trees to be illuminated equally. If the transparency is not good for you, try to decrease the MipMapBias (try -4) of the diffuse texture in the material dialog. Probably, those two procedures will improve the tree's appearance a lot.
