There exists different types of cells within a plant, each type serving a purpose. Hence, chloroplasts allow for a plant to absorb the sunlight energy, being involved in photosynthesis process, while cell walls allow for the structure of a plant to be rigid.
Since potato is a vegetable root and it does not need sunlight for growing inside soil, it has no chloroplasts because it is not directly exposed to sunlight.
Plant cells can be recognized at a simple examination of their structure. Unlike animal cells, plant cell structure does not contain cilia, flagella, lysosomes, centrioles, intermediate filaments, but they do contain rigid cell wall and plasmodesmata, chloroplasts and central vacuole.