The correct answer to this question is this: Plant cells that are being placed first in a medium for the purpose of the tissue culture are differentiated cells. Pluripotent cells or cells that are able to develop into all the specialized cell types and structures of plants are being produced by undifferentiated cells.
Plant cells and the embryonic stem cells of an animal are mostly similar to each other. First, they develop in a tissue culture where it is easier to develop into a different cell type and structure.