By Derek Plastids are cells that store specific things.
Plastids form small colorless bodies called proplastids.
Once formed certain kinds of plastids can be converted into other types. Chloroplasts contain chlorophyll which contains green pigment and some carotenoids which hold yellow or orange pigment. Leucoplasts are organelles where starch, oil and protein are stored. Chloroplasts Chloroplasts serve as the site of photosynthesis. Leaves have about 500,000 chloroplasts per square millimeter of the surface.