could we find differences among cells from different parts of a plant body ?

Yes, we can find differences in cells from various parts of the plant body. There are different types of cells in a plant body. They have different structures and perform different functions. So, root cells would differ from the types of cells present in leaves or stem.  For example: Leaf contains a number of different cells like mesophyll cells, bundle-sheath cells, guard cells which are not present in other parts of plant body.